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1
Hu, Rong. "Irradiation effects on Fe-Cr alloys". Thesis, University of Oxford, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.560928.
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Ferritic chromium steels are important structural materials for future nuclear fission and fusion reactors due to their advantages over traditional austenitic steels, including low swelling rates, better thermal fatigue resistance, and lower thermal expansion coefficients. Radiation-induced segregation or depletion (RIS/RID) of solute atoms at grain boundaries is considered to be a potentially significant phenomenon for structural materials because of its potentially detrimental role in affecting microstructure and furthermore mechanical properties. However, the behaviour of Cr at grain boundaries in ferritic steels is not well understood. Both segregation and depletion of Cr at grain boundary under irradiation have been previously observed and no clear dependency on irradiation condition or alloy type has been presented. Furthermore, ferritic alloys are known to undergo hardening and embrittlement after thermal aging in the temperature range of 300-550DC and this phenomenon is related with a and a' phase separation occurring in the solid solution. However the low temperature a-a' miscibility gap in the currently used phase diagram is extrapolated from high temperature results and conflicts with many experimental observations. To understand the Cr behaviour at gram boundaries in ferritic steels under irradiation, a systematic approach combining SEM/EBSD, FIB specimen preparation and APT analysis has been developed and successfully applied to a Fe- 15.2at%Cr to investigate the effect of pre-irradiation chemistry, grain boundary misorientation, impurities, irradiation damage, irradiation depth, and other possible factors to get a better understanding of RIS/RID phenomena. Both low sigma boundaries and randomly selected high angle boundaries have been investigated in detail. Systematic differences between the behaviour of different classes of boundaries had been observed, and the operating mechanisms are also discussed in this thesis. The maximum separation method has been applied on APT data to study the C- enriched clusters and Cr-enriched clusters, which were not directly visible on the atom maps. The composition of the Cr-enriched clusters was consistent with a' phase and the irradiation was found to accelerate the nucleation rather than the growth of these clusters. Such results provided important information in re- determining the a-a' phase boundary.
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Xu, Sen. "Characterisation of radiation damage in Fe-Cr-Alloys". Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534015.
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Ferguson, David Bruce. "Characterization of high damping Fe-Cr-Mo and Fe-Cr-Al alloys for naval ships application". Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/22942.
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The metallurgical basis for high damping in Fe-Cr-based alloys was investigated. Two alloys similar to VACROSIL-010 were studied, with compositions of 84.7 Fe-11.44 Cr-2.91 A1 and 84.8 Fe-11.65 Cr-2.92 Mo. The strain dependence of specific damping capacity (SDC) was evaluated using a modified version of the resonant dwell technique. Heat treatment variations were introduced by annealing in argon gas at temperatures between 950 C and 1100 C and then furnace cooling. Cantilever beam specimens were evaluated for SDC at their first three resonant modes (0-1,000 Hz) at room temperature. Changes in damping capacity were correlated with the results of tensile hysteresis testing and dilatometry. Keywords: Damping; Ship silencing; Ferritic stainless steels
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Sorour, Ahmad. "Microstructure and tribology of Fe-Cr-B-based alloys". Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123081.
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Wear causes loss of materials of moving parts and tools used in many fields. Wear can be reduced by employing appropriate materials and coatings, which requires an understanding of their microstructure, properties and tribological behavior. One of the high wear resistant materials is the Fe-Cr-B-based alloy system. Fe-Cr-B-based alloys have been fabricated using thermal spray, welding and sintering processes; and it has been found that their microstructure, properties and tribological performance vary from process to process. This dissertation focuses on advances made by employing recent processes to fabricate these alloys. The primary aim of this research is to understand the microstructure and tribology of the Fe-Cr-B-based alloys fabricated by the controlled short-circuit metal inert gas (CSC-MIG) welding and spark plasmasintering (SPS) processes.CSC-MIG was used to weld a Fe-28.2Cr-3.8B-1.5Si-1.5Mn (wt.%) cored wire alloy onto 1020 carbon steel substrate. SPS was employed to consolidate a Fe-45Cr-5.9B-2Si-0.1C (wt.%) gas-atomized powder alloy. Solidication behaviors of the gas-atomized powder and weldments were investigated through thermodynamiccalculations. Microstructure characterizations, hardness measurements and tribology testings were performed for these fabricated alloys.Upon cooling, the primary (Cr,Fe)2B phase began to form, followed by eutectic formation of the (Cr,Fe)2B and body-centered cubic (BCC) Fe-based solid solution phases. Because the powder contained a small amount of C, (Cr,Fe)7C3 was precipitated at the end of the solidication. The CSC-MIG weldment was composed of 44 wt.% primary and secondary orthorhombic (Cr,Fe)2B plates embedded in 56 wt.% BCC Fe-based solid solution, containing Fe, Cr, Mn and Si. The SPS specimen contained 65 wt.% (Cr,Fe)2B plates and 1 wt.% (Cr,Fe)7C3 precipitates dispersed in 34 wt.% BCC Fe-based solid solution, containing Fe, Cr and Si. The (Cr,Fe)2B phase was bigger in the weldment than the sintered specimen. The hardness of (Cr,Fe)2B was 24 GPa, independent of the alloy's composition and process parameters. As the B content increased, the fraction of (Cr,Fe)2B increased. As the (Cr,Fe)2B fraction increased, the bulk hardness of the specimens increased linearly. When the specimen's hardness and (Cr,Fe)2B size increased, abrasive wear resistance increased, while sliding wear resistance was independent of hardness but improved as the (Cr,Fe)2B size increased. The abrasive wear mechanism was microcutting, while sliding wear mechanisms were adhesion and mild oxidation.L'usage cause la perte du materiel de pieces mobiles et d'outils utilises dans plusieurs domaines. L'usage peut ^etre reduit en utilisant des materiaux appropries et des rev^etements dont l'utilisation demande la comprehension de leure microstructure, leures proprietes et leur comportement tribologique. Un des materiaux aillant une haute resistance a l'usage est le systeme d'alliage Fe-Cr-B. Les alliages a base Fe-Cr-B sont fabriques par pulverisation thermal, soudure et des processus de frittage. C'etait decouvert que la microstructure, les proprietes et la performance tribologique varie d'une procede a l'autre. Cette dissertation est centre sur les avances concues en utilisant des recentes procedes pour fabriquer ces alliages. Le but primaire de cette recherche est de comprendre la microstructure et la tribology des alliages Fe-Cr-B fabriques par soudure controlled short-circuit metal inert gas (CSC-MIG) et frittage ash (SPS).CSC-MIG etait utilise pour souder un alliage llamente Fe-28.2Cr-3.8B-1.5Si-1.5Mn (wt.%) sur un substrat d'acier 1020. SPS etait utilise pour consolider un alliage en poudre Fe-45Cr-5.9B-2Si-0.1C (wt.%) fabrique par atomization a gaz. Les comportements de solidication du poudre atomize par gaz et des soudures etaient etudies a travers des calculs thermodynamiques. Une caracterisation microstructurielle, des mesures de durete et des tests de tribology etaient performes pour ces alliages. Durant la refroidissement, la phase primaire (Cr,Fe)2B a commence a se developper suivi par une formation eutectique du (Cr,Fe)2B et de la phase en solution solide corps-centre cubique (BCC) a base de fer. Puisque la poudre contenait des petites quantites de C, le (Cr,Fe)7C3 a precipite a la n du solidication. La soudure CSC-MIG etait composee de plaques orthorhombiques de phase primaire et secondaire de (Cr,Fe)2B a 44 wt.% integre dans 56 wt.% d'une solution solide a base de Fe BCC content du Fe, Cr, Mn et Si. Le specimen prepare par SPS contenait des plaques de 65 wt.% (Cr,Fe)2B et des precipites de 1 wt.% (Cr,Fe)7C3 dispersees dans une solution solide a base de Fe BCC de 34 wt.% aillant du Fe, Cr et Si. La phase (Cr,Fe)2B etait plus grand dans la soudure que dans le specimen fritte. La durete du (Cr,Fe)2B etait 24 GPa sans dependance sur la composition de l'alliage ni les parametres de procede. Pendant que la quantite de B s'accroissait, la fraction du (Cr,Fe)2B s'accroissait aussi. Pendant que la fraction de (Cr,Fe)2B s'accroissait, la durete entiere des specimens s'accroissait d'une facon lineaire. Quand la durete du specimen et la taille du (Cr,Fe)2B s'accroissaient, la resistance abrasif d'usage s'accroissait pendant que la resistance glissant d'usage etait independant de la durete mais s'ameliorait pendant que la taille du (Cr,Fe)2B s'accroissait. Le mechanism de l'usage abrasif etait la microcoupure pendant que le mechanism de l'usage glissant etait l'adhesion de l'oxidation mineure.
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Sorsh, Frans. "Assessment of creep damage in Fe-Ni-Cr alloys". Thesis, KTH, Hållfasthetslära (Avd.), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259516.
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It is only a matter of time before components working in high temperature environments fail due to creep. Design for creep is therefore of vital importance to maximize the lifetime of components and reduce costs that may arise from maintenance and replacement of components. This thesis aims to use metallographical methods and finite element modeling to assess creep damage in a hydrogen reformer. The decommissioned reformer, made of Fe-Ni-Cr alloys, was investigated thoroughly via replica testing, hardness measurements as well as finite element modeling of the welds. An extended literature review was performed to gain a better understanding of creep in Fe-Ni-Cr alloys, welds and the modeling of creep generally. The microstructures of samples from the reformer were analyzed and mapped out in terms of creep damage which were then compared to a creep analysis of the welds with a simulation time of 100 000 h. The FE results yielded high stresses and creep strains with a maximum of 0.95% in the boundaries of the welds which gave realistic representations of strain distributions when compared to the metallographical results. Hardness measurement indicated that a relatively narrow zone with altered mechanical properties is present along the weld boundaries. This area, called the heat affected zone, was found to be most affected by creep with microcracks reaching maximum lengths of 2 mm. The creep strains obtained from simulation did not fall in line with the observed creep damage, it was thus concluded that a material model that considers tertiary creep would yield a more realistic representation in FEM for Fe-Ni-Cr alloys.Det är bara en tidsfråga innan komponenter som arbetar i högtemperaturförhållanden misslyckas pga kryp. Att designa med avseende på kryp är därmed viktigt för att maximera livslängden och reducera kostnader som kan komma från underhåll och från utbyte av komponenter. I detta examensarbete används metallografiska metoder och finita element modellering för att bedöma krypskador i en vätgasreformer. Vätgasreformern, som är tillverkad i Fe-Ni-Cr legeringar, togs ur drift och undersöktes metallografiskt med hjälp av replikprovning och hårdhetsprovning samt med finita element modellering av svetsar. En djupgående litteraturstudie utfördes för att öka förståelsen av kryp, specifikt i Fe-Ni-Cr legeringar och även modellering av kryp generellt. Mikrostrukturen från utvalda provbitar undersöktes och krypskador kartläggdes för att sedan jämföra med en krypanalys av svetsarna där 100 000 timmars kryp simulerades. Krypanalysen resulterade i höga spänningar och kryptöjningar upp till maximalt 0.95% i svetsgränserna vilket gav realistiska representationer av töjningsdistributionen jämfört med metallografiska resultaten. Hårdhetsmätningar indikerade att ett smalt område med förändrade mekaniska egenskaper fanns utmed svetsgränserna. Detta område, den värmepåverkade zonen, var mest utsatt för krypskador med mikrosprickor uppemåt 2 mm i längd. Kryptöjningar som erhölls från simuleringen gav inte en tillräckligt bra uppskattning av kryptöjningarna – de krypskador som observerades motsvarar lokalt högre töjning. Slutsatsen är att en materialmodell som tar hänsyn till tertiärkryp skulle i det här fallet ge en mer realistisk representation i FEM för Fe-Ni-Cr legeringar.
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Pan, Li-Mei. "Phase equilibria and elastic moduli of rapidly solidified Fe-Cr-Mo-B and Fe-Cr-Ni-B alloys". Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/2387/.
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Zhou, Jing. "Experimental study of phase separation in Fe-Cr based alloys". Licentiate thesis, KTH, Metallografi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119230.
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Duplex stainless steels (DSSs) are important engineering materials due to their combination of good mechanical properties and corrosion resistance. However, as a consequence of their ferrite content, DSSs are sensitive to the so-called ‘475°C embrittlement’, which is induced by phase separation, namely, the ferrite decomposed into Fe-rich ferrite (α) and Cr-rich ferrite (α'), respectively. The phase separation is accompanied with a severe loss of toughness. Thus, the ‘475°C embrittlement’ phenomenon limits DSSs’ upper service temperature to around 250°C. In the present work, Fe-Cr binary model alloys and commercial DSSs from weldments were investigated for the study of phase separation in ferrite. Different techniques were employed to study the phase separation in model alloys and commercial DSSs, including atom probe tomography, transmission electron microscopy and micro-hardness test. Three different model alloys, Fe-25Cr, Fe-30Cr and Fe-35Cr (wt. %) were analyzed by atom probe tomography after different aging times. A new method based on radial distribution function was developed to evaluate the wavelength and amplitude of phase separation in these Fe-Cr binary alloys. The results were compared with the wavelengths obtained from 1D auto-correlation function and amplitudes from Langer-Bar-On-Miller method. It was found that the wavelengths from 1D auto-correlation function cannot reflect the 3D nano-scaled structures as accurate as those obtained by radial distribution function. Furthermore, the Langer-Bar-On-Miller method underestimates the amplitudes of phase separation. Commercial DSSs of SAF2205, 2304, 2507 and 25.10.4L were employed to investigate the connections between phase separation and mechanical properties from different microstructures (base metal, heat-affected-zone and welding bead) in welding. Moreover, the effect of external tensile stress during aging on phase separation of ferrite was also investigated. It was found that atom probe tomography is very useful for the analysis of phase separation in ferrite and the radial distribution function (RDF) is an effective method to compare the extent of phase separation at the very early stages. RDF is even more sensitive than frequency diagrams. In addition, the results indicate that the mechanical properties are highly connected with the phase separation in ferrite and other phenomena, such as Ni-Mn-Si-Cu clusters, that can also deteriorate the mechanical properties.QC 20130308
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EverhartC, Charles. "The Electrodeposition of Fe-Ni-Cr Alloys from Aqueous Electrolytes". Cleveland, Ohio : Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1252092401.
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Thesis(M.S.)--Case Western Reserve University, 2009Title from PDF (viewed on 2010-01-28) Department of Chemical Engineering Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
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Koseki, Toshihiko 1958. "Undercooling and rapid solidification of Fe-Cr-Ni ternary alloys". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/12040.
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Flores, Carlos D. (Carlos Daniel). "Evaluation of radiation induced segregation in Fe-Ni-Cr alloys". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/44597.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering; and, (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1994.Includes bibliographical references.
by Carlos D. Flores.
M.S.
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Hardie, Christopher David. "Micro-mechanics of irradiated Fe-Cr alloys for fusion reactors". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:a3ac36ba-ca6f-4129-8f37-f1278ef8a559.
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In the absence of a fusion neutron source, research on the structural integrity of materials in the fusion environment relies on current fission data and simulation methods. Through investigation of the Fe-Cr system, this detailed study explores the challenges and limitations in the use of currently available radiation sources for fusion materials research. An investigation of ion-irradiated Fe12%Cr using nanoindentation with a cube corner, Berkovich and spherical tip, and micro-cantilever testing with two different geometries, highlighted that the measurement of irradiation hardening was largely dependent on the type of test used. Selected methods were used for the comparison of Fe6%Cr irradiated by ions and neutrons to a dose of 1.7dpa at a temperature of 288°C. Micro-cantilever tests of the Fe6%Cr alloy with beam depths of 400 to 7000nm, identified that size effects may significantly obscure irradiation hardening and that these effects are dependent on radiation conditions. Irradiation hardening in the neutron-irradiated alloy was approximately double that of the ion-irradiated alloy and exhibited increased work hardening. Similar differences in hardening were observed in an Fe5%Cr alloy after ion-irradiation to a dose of 0.6dpa at 400°C and doses rates of 6 x 10-4dpa/s and 3 x 10-5dpa/s. Identified by APT, it was shown that increased irradiation hardening was likely to be caused by the enhanced segregation of Cr observed in the alloy irradiated with the lower dose rate. These observations have significant implications for future fusion materials research in terms of the simulation of fusion relevant radiation conditions and micro-mechanical testing.
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Techaboonanek, Chanachon. "Precipitation during Tempering of Martensite in Fe-Cr-C alloys". Thesis, KTH, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103192.
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The martensite structure is the most important microstructure in tool steel due to its high hardness. However, a lack of ductility is the major drawback. In order to improve the ductility and still maintaining a suitable hardness a tempering process is needed. The tempering process will cause recovery and recrystallization in the matrix, and moreover carbides will precipitate. The specific carbides have different characteristics and thus the type of carbide formed during tempering is very important for the properties of the steel. The simulation software (TC-Prisma) is interesting because it can predict type, size, and amount of carbides. The present study was carried out to investigate both the microstructure, hardness evolution of martensite and precipitation which occurred in Fe-C-Cr steel with different compositions, tempered at 700oC. The experimental results were compared with simulation results. Micro-Vickers hardness test with a load of 100 g was used and the hardness value dropped 40% and 60% in low carbon alloy and high carbon alloy steels, respectively. The significant drop occurred during the first 30 seconds of tempering due to recovery of the matrix. Hardness values slightly decreased and then stabilized during continued tempering. The microstructure of martensite and the morphology of carbides at different tempering times were examined by scanning and transmission electron microscopy in order to study the precipitation of carbides from the nucleation and growth to coarsening. There are three types of carbides which precipitated in the Fe-C-Cr specimens: M7C3, cementite and M3C2 depending on the composition. Fe-0.16C-4.05Cr contained M7C3, Fe-0.95C-1.065Cr contained cementite and M3C2 and Fe-014C-0.983Cr and Fe-0.88C-4.12Cr contained M7C3 and cementite. M7C3 has a faceted shape and precipitates referentially at grain boundaries. On the other hand, cementite has an elongated shape and precipitated mainly at grain boundaries but also intragranulary. M3C2 has a rounded shape and was seen only in very small amounts, and seemed to precipitate at random sites. The trend of carbide growth in experiments is consistent with the simulations using TC-Prisma, but more work is needed to enable quantitative comparisons.
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Higginson, A. "The passivation of Fe-Cr-Ru alloys in acidic solutions". Thesis, University of Manchester, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488143.
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Jung, Kyung Sub [Verfasser] y Eric J. [Akademischer Betreuer] Mittemeijer. "Nitriding of iron-based ternary alloys : Fe-Cr-Ti and Fe-Cr-Al / Kyung Sub Jung. Betreuer: E. J. Mittemeijer". Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2011. http://d-nb.info/1014148138/34.
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Tappin, David Keith. "The characterisation of displacement cascades in austenitic Fe-Cr-Ni alloys". Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317254.
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Clauß, Arno Rainer. "Nitriding of Fe-Cr-Al alloys nitride precipitation and phase transformations /". Stuttgart : Max-Planck-Inst. für Metallforschung, 2008. http://d-nb.info/995395918/34.
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Watson, Maxine. "Phase stability, constitution and precipitation effects in Fe-Ni-Cr alloys". Thesis, Sheffield Hallam University, 1990. http://shura.shu.ac.uk/20503/.
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A study of the constitution, transformation and precipitation effects in ternary Fe-Cr-Ni alloys and quaternary Fe-Cr-Ni-X alloys containing Mo, Nb, Ti, and Si was carried out. A systematic approach was adopted so that the microstructural effects observed as a result of ageing the selected iron base ternary alloys could be directly compared to the quaternary alloys. A series of ageing curves were plotted for the six ternary alloys over the temperature range 400°-900°C and for the ten quaternary alloys in the temperature range 650°-850°C. Optical and electron metallography were used to study the transformation and precipitation of intermetallic phases and carbides in the aged microstructures. The transformation of delta ferrite to sigma phase in a duplex (gamma+delta) ternary alloy was studied. The transformation was preceded by the precipitation of a cellular structure which formed on the delta/gamma grain boundaries and consisted of M23C6 and new austenite. A complex transformation product, which resembled a region of imiscibility, then formed at the delta/(gamma + M23C6) interface, this product consumed the delta ferrite grain, eventually transforming to sigma phase and new austenite. The alpha' phase, more commonly referred to as 475°C embrittlement, was also observed precipitating in the delta ferrite grains in two of the iron based ternary alloys in the temperature region 400°-500°C. Overageing of the alpha' precipitates after 1000 hours at 500°G was accompanied by the precipitation of a rod like austenite. The elements 2%Mo, 1%Nb, 1/4%Ti and 1% and 2%Si were added totwo Fe-Ni-Cr base alloys. One alloy was an austenitic (20Cr,23Ni) and the other was a transformable alloy (18Cr, 7Ni). The quaternary element additions had no effect on the constitution of the austenitic ternary alloy. However the addition of Mo to the 18Cr, 7Ni ternary alloy caused the transformation of delta ferrite to sigma phase over ageing temperature range 650°-850°C. The addition of Si moved the constitution of the ternary alloy further into the gamma+delta phase field, a small amount of sigma phase was observed in the 2%Si quaternary alloy on ageing at 650°C for 1000 hours. Irradiation damage studies were performed using High Voltage Electron Microscope and Variable Energy Cyclotron. The effect ofthe quaternary alloying additions Mo, Si, and Nb on the voidswelling behaviour of a 20Cr, 23Ni alloy were studied using 46MeV Ni6 ions in the Variable Energy Cyclotron, irradiating to a total dose of 10dpa at 550°C. All additions reduced void swelling, the largest reduction was observed in the Si containing allov. The Insert A Thermal ageing showed the presence of M23C6 the amount of which increased with increasing ageing temperature. No delta ferrite was observed in these alloys.
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Xu, Shuo. "A study of irradiation damage in iron and Fe-Cr alloys". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:fec4b2d0-411e-4c20-862d-e5fd884367f3.
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Irradiation damage structures induced in pure Fe and Fe-Cr (up to 14%Cr) alloys by 2 MeV Fe+ ion irradiations in the temperature range 300-460°C were investigated by transmission electron microscopy. Specimens were irradiated in bulk to doses of 1.5 x 1019 Fe+/m2 (about 2.5 displacements per atom: dpa) and 4.5 x 1019 Fe+/m2 (about 7 dpa). In most cases, damage took the form of dislocation loops with diameters from 2-100nm; the loops were distributed uniformly within all the samples. At higher irradiation temperatures (400°C, 460°C), complex microstructures such as finger loops (50nm in width and 1 micron in length) and perpendicular <100> loop clusters, were observed in both pure Fe and Fe-Cr samples. Loop sizes and densities were seen to change as a function of irradiation temperature and dose. Loop sizes were seen to increase as the increase of irradiation temperatures and doses, while loop densities only increased with increasing doses and decreased as increasing temperatures. Loops with both types of Burgers vectors (<100> and ½<111>) were observed in all the samples. The proportion of <100> loops was higher in Fe than that in Fe-Cr alloys at the same irradiation condition, which has can be attributed to the high mobility of ½<111> loops in Fe, so that a large proportion of them will escape to the (001) foil surface. A transition in loop Burgers vectors as a consequence of increasing temperature was observed. In Fe, the proportion of <100> loops increased with increasing irradiation temperature from 40% at 300°C to 60% at 460°C. A similar trend was found in the Fe-Cr alloys, but due to the higher proportion of ½<111> loops in these alloys, the increase of <100> loops was not that obvious, being from 30% at 300°C to 45% at 460°C(Fe-11Cr). The effects of irradiation dose rate on the formation of dislocation loops by 2 MeV Fe+ ions were also investigated. These irradiations were carried out at 300°C with two different implantation dose rates: 6 x 10-4 dpa/s and 3 x 10-5 dpa/s. The implantation dose for both implantations was 0.38 x 1019 Fe+/m2 (0.5 dpa). Both the average loop size and loop densities for the Fe-Cr specimens subjected to the high dose rate irradiation were higher than that in the low dose rate irradiations. Take Fe-14Cr as an example, that the loop densities in high dose rate irradiation increased about 90% compared to that in low dose rate, and the average loop size in high dose rate irradiation was 30% larger than that in low dose rate irradiation. The ‘inside-outside contrast’ method was applied to determine the loop nature in all the samples. It was found that all the large loops (>5nm) are of interstitial type. Any vacancies are believed to exist in the form of small dislocation loops (<5nm) or sub-microscopic voids.
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Matsumoto, Jun. "Electrochemistry of intermetallic phases of Ni-Cr-Fe alloys in aqueous environment". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13439.
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Maloney, Michael. "Rapid solidification processing and oxidation of fine grained Fe-Cr-Al alloys". Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/89250.
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Kish, Joseph J. "Active-passive corrosion of Fe-Cr-Ni alloys in hot concentrated sulphuric acid solutions /". *McMaster only, 1999.
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KUNIOSHI, CLARICE T. "Obtencao e caracterizacao de ligas metalicas amorfas Fe-Cr-P eletrodepositadas". reponame:Repositório Institucional do IPEN, 1998. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10696.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Ward, Michael C. L. "An EXAFS structural study of the passive films formed on Fe-Cr alloys". Thesis, University of Warwick, 1986. http://wrap.warwick.ac.uk/50791/.
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Comparatively little is known about the nature of the passive films formed upon the technologically important iron-chromium alloys. It is known however, that they are both very thin (50A) and possibly amorphous: as such they are difficult to characterize by conventional diffraction methods. To avoid the problems associated with the diffraction techniques, the EXAFS technique has been used to characterize the passive film. Iron-chromium alloys containing up to 29% atomic chromium were passivated in 0.1M NaNO2, 0.05M K2CrO4 and 2.0M H2S04. X-ray absorption measurements were then made upon the passivated alloys, using both total electron yield and fluorescence yield to determine the X-ray absorption. Analysis of the extended X-ray absorption fine structure has revealed that an increase in structural disorder of the passive film may be correlated with an increase in the chromium content of the alloy. It has been shown that chromium contained in the passive film is associated with the disorder in the film Fe-O and Fe-Fe bond lengths compatible with the known oxides and hydroxides of iron have been obtained, but the uncertainties in the bond length determination prevent any structure being put forward for the passive film.
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Pleune, Thomas Todd 1974. "Integrated environmental degradation model for Fe-Ni-Cr alloys in irradiated aqueous solutions". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/84224.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1999.Includes bibliographical references.
An integrated model has been developed to evaluate the effect of reactor flux, fluence, and other operating conditions on crack growth rates in austenitic stainless steels in boiling water reactor (BWR) environments. The model evaluates the following in order to account for all factors affecting irradiation assisted stress corrosion cracking. *water chemistry including radiolysis and hydrogen injection *radiation induced segregation of the metal *radiation hardening of the metal *crack tip strain rate of a growing crack *dissolution rate at the crack tip following passive film rupture. The results of each of these models are combined to determine the crack advance rate for the given conditions. Environmentally assisted cracking (EAC) is a phenomenon where a combination of aggressive environment, susceptible material, and significant tensile stress result in accelerated degradation, including stress corrosion cracking (SCC), and hydrogen embrittlement. The EAC model is based on first principles electrochemistry and physical metallurgy. The effect of neutron and gamma radiation dose is included so that irradiation assisted stress corrosion cracking can be studied. By integrating the bulk chemistry with crack tip processes, the crack growth behavior of an aqueous system can be completely characterized. The model integrates chemistry and mechanical behavior to allow the study of EAC in general.
(cont.) EAC phenomena of interest include anodically driven stress corrosion cracking as well as cathodically driven hydrogen embrittlement. The model is able to predict measured data in the literature with good accuracy and precision. It predicts the effects of dose-rate and accumulated dose on stress corrosion cracking in BWRs. This model contributes to the field of crack growth modeling by creating a complete picture including all the major factors effecting crack growth in irradiated systems.
by Thomas Todd Pleune.
Ph.D.
25
Goodwin, Paul S. "Microstructures and properties of rapidly solidified Al-Cr-Fe alloys for aerospace applications". Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/842855/.
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The development of aluminium alloys capable of elevated temperature service by utilization of Rapid Solidification (RS) processing techniques has been an area of intense study during the past decade. The ternary alloy system, Al-Cr-Fe, has displayed very promising mechanical properties when produced by an evaporation-vapour deposition technique, but little indication exists of whether similar properties may be achievable by using other, more commercially applicable, RS techniques. This work comprises a study of the microstructure and tensile properties of a range of Al-Cr-Fe alloys (Al-2.93 to 8.43 wt% Cr-0.67 to 2.07 wt% Fe) processed by high pressure gas atomisation (HPGA), supplemented by additional experiments using melt-spinning and chill-casting techniques in order to allow the effects of a wide range of cooling rates (< 1k/s to 106K/s) to be examined. A series of binary Al-Cr alloys (Al-1.99 to 5.50 wt% Cr) were also processed in order to facilitate comparison with the ternary alloys. The variety of microstructures observed in the atomised powders were consistent with the different cooling rates and nucleation temperatures experienced by droplets of different diameters. The cooling rate necessary to suppress formation of the Ali3Cr2 phase was found to be consistently higher in the ternary alloys than in the corresponding binaries. No evidence was found of partitionless solidification having occurred in the Al-Cr-Fe powders, the estimated solidification front velocities being insufficient to prevent the partitioning of the iron to the infinity-aluminimum cell boundaries. The infinity-aluminium phase was found to be divided into two co-existing, but distinct, solid solutions with different chromium solute levels. A fine spherical phase was observed in the finest particles of the most concentrated alloy (Al-8.43 wt% Cr-1.26 wt % Fe), which was found to be similar to the icosahedral phase identified in the melt-spun ribbon. A relationship has been determined between the thickness of wedge shaped chill castings and powder particle diameters for similar microstructural transitions. A procedure is proposed by which the determination of alloy compositions designed to give a particular microstructure in a specific powder size fraction can be accomplished by a simple chill casting technique. The mechanical properties of the atomised powders consolidated by extrusion have been determined and related to the microstructures and strengthening mechanisms operative in the materials. A large contribution to the strength of the extruded materials is derived from their fine grain size. However, none of the atomised Al-Cr-Fe alloys matched the properties obtained in the Al-7.5 wt% Cr-1.2 wt% Fe alloy material produced by the vapour deposition technique. None of the alloys investigated retained its strength after prolonged thermal exposure at or above 350°C, nor possessed adequate tensile strength properties at 350°C. The results do suggest, however, that a service temperature of 300°C may be possible.
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Kish, Joseph R. "Active-passive corrosion of Fe-Cr-Ni alloys in hot concentrated sulphuric acid solutions". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0022/NQ50995.pdf.
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Hou, Ziyong. "Study of precipitation in martensitic Fe-C-Cr alloys during tempering : Experiments and modelling". Licentiate thesis, KTH, Metallografi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176430.
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Understanding the precipitation reaction is very important since precipitation hardening is one of the most effective strengthening mechanisms in metallic alloys. In martensitic steels, a tempering heat treatment is often performed. During tempering various new phases are precipitated and the spatial and temporal evolution of these precipitates strongly influences the properties of the steel, such as strength/ductility, creep, fatigue and hot corrosion resistance. Therefore, the possibility of quantitative modelling of the precipitation process will provide many opportunities for advanced materials and process design and optimization as well as service life assessments. The Fe-C-Cr system forms the basis for tool steels and is consequently used in many applications such as e.g. metal forming operations. They are characterized by a high hardness and good toughness, even at elevated temperatures.In the present work, the as-quenched martensitic microstructures of four Fe-C-Cr alloys with varying Cr and C contents were characterized by Light Optical Microscopy (LOM) and Electron Microscopy. The effects of Cr and C on the morphology of martensite were investigated. It was found that Cr addition had a similar effect as C on the martensitic morphology and on the ratio of high-angle grain boundary (HAGB) to low-angle grain boundary (LAGB). However, the micro-hardness was unaffected by the Cr addition whilst it was strongly influenced by the C addition.In addition, a quantitative experimental characterization of the precipitates formed during tempering of the martensite was performed. The Langer-Schwartz theory combined with the Kampmann-Wagner-Numerical (KWN) method, as implemented in the software TC-PRISMA, was used to predict the precipitation of carbides after tempering in one of the model alloys: Fe-0.15C-4.0Cr (mass%). The microstructure characterization of the as-quenched material provided vital input parameters for the modelling work and a comparison was made between the modelling predictions and the experimental results. The effect of parameters such as dislocation density, grain size and interfacial energy on the precipitation of carbides was discussed.QC 20151105
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King, Simon L. "The interaction of HVEM generated point-defects with dislocations in Fe-Ni-Cr alloys". Thesis, University of Oxford, 1990. http://ora.ox.ac.uk/objects/uuid:b9b6a0fa-a180-40fe-be48-7c28fc369ca1.
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The climb of dissociated dislocations in FCC materials is known to be complex: Observations of climb under HVEM irradiation in CuAl suggest that it, proceeds via the nucleation of interstitial loops directly onto individual partials. In silver, however, dissociated dislocations appear to constrict at an early stage in the irradiation, and dense vacancy cluster damage is seen to form in their vicinity. This thesis presents results and analysis of a study aimed at the determination of the interaction of HVEM generated interstitials and vacancies with pre-existing dislocations in a range of Fe-17Cr-Ni ternary alloys (with the nickel content varying between 15 and 40%). Two quaternary alloys (Fe-15%Ni-17%Cr-l%Si and Fe-15%Ni-17%Cr-2%Mo) arc also studied. As with earlier studies in CuAl and Ag, pre-existing dislocations in a (111) orientated foil were first characterized at subthreshold voltages employing the weak-becim technique, then irradiated with IMeV electrons at temperatures in the range 400-430°C and finally returned to the low voltage microscope for postirradiation characterization of the observed damage. Analysis of the post-irradiation microstructures indicates that interstitial climb only occurs at particularly favourable sites, such as pre-existing jogs: For the ternary alloys, constrictions are removed along edge and mixed dislocations, whilst zig-zagging of screw and near-screw dislocations may also be attributable to jog climb. After the annihilation of constrictions evidence of climb is not seen and pipe diffusion is thought to be occurring. The precipitation of small clusters, many of which are identifiable as vacancy SFT, is reminiscent of observations in silver. The addition of silicon to the matrix apparently leads to the creation of favourable sites for interstitial climb, as evidenced by the formation of high densities of new jogs after irradiation. Loops are seen to precipitate close to dislocations in the Mo-doped material. The origin of these loops is unclear at this stage. The relevance of the results to the phenomenon of void swelling is discussed.
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Li, Zhen. "SURFACE HARDENING OF AUSTENITIC FE–CR–NI ALLOYS FOR ACCIDENT-TOLERANT NUCLEAR FUEL CLADDING". Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case150486174877088.
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Perks, Jonathan Michael. "Phosphorus segregation and diffusion in nickel and Fe-Cr-Ni alloys under fast particle irradiation". Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329993.
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Janis, Jesper. "Inclusions and/or Particles Engineering for Grain Refining Purposes in Ferritic Fe-20mass%Cr alloys". Doctoral thesis, KTH, Tillämpad processmetallurgi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-13012.
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Compared to more common used austenitic stainless steels, ferritic stainless steels contain very low amounts of the expensive alloying element Ni. In addition, they have good corrosion properties, but are sometimes suffering from poor weldability and bad mechanical properties. This is mainly due to the presence of large grains after casting and large grain growth during heat treatment or welding. Processes for reducing the grain size (grain refining) of metal alloys are widely known and proven before to be suitable for many alloys. A successful grain refining process can increase the strength of an alloy without decreasing the ductility. This can be achieved by different methods, such as rolling or cooling. In this work, the focus has been on studying the aspect from a metallurgist point of view, to analyse the possibilities to create small particles in the liquid stage to enhance the solidification. The focus has been on oxide and nitride formation for nucleation of smaller grains during solidification. This study was made by forming particles, develop the analysis methods and thereafter to study the effect of particles on the structure of a ferritic stainless steel. The particles were formed by additions of Ti, Ce and Zr in to a liquid Fe-20mass% Cr alloy containing different amounts of oxygen and nitrogen. The electrolytic extraction technique was used to achieve a good understanding of the reaction processes and the particles size, number, composition and morphology. The grain sizes and the particles were then studied in as-cast samples as well as in specimens heat treated for 60 minutes at 1200, 1300 and 1400°C in a Confocal Scanning Laser Microscope (CSLM). Also, based on Scanning Electron Microscope (SEM) determinations and Thermo-Calc calculations, the precipitated particles were divided as primary and secondary particles. Thereafter, the grain refining potential was studied for each of these types. In this work, particles engineering by using small particles have been proven suitable for the Fe-20mass% Cr ferritic stainless steel alloys. Although the work has been based on small-scale samples and experiments, the results show good tendencies with respect to grain refining as well as a clear relationship between the particles in the steels and the microstructures. It was found that Ti-Ce additions in Fe-20mass% Cr alloys resulted in complex oxides including Ti, Ce and Cr. These oxides were observed to have high agglomeration tendencies and therefore to form larger particles or clusters. The grain refining potential on the solidification structure was insignificant, despite a relatively large amount of particles. However, Ti-Zr additions in Fe- 20mass% Cr alloys on the other hand resulted in primary precipitated particles such as ZrO2 and ZrO2+ZrN. Furthermore, ZrN nucleated ferrite during solidification, which lead to a clearly observed grain refining effect. This effect was also increased with an increased number of particles. The amount of particles (primary and secondary) was also found to increase with an increased amount of nitrogen. Secondary particles (mostly TiN) were precipitated near grain boundaries, which lead to a location based pinning effect of the grain growth during heat treatment at 1200 °C. This pinning effect was increased by an increased nitrogen content and thereby an increased number of particles. Finally, the pinning effect was clearly reduced during heat treatment at 1400 °C.QC20100524
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Razumovskiy, Vsevolod. "Thermodynamic and kinetic properties of Fe-Cr and TiC-ZrC alloys from Density Functional Theory". Doctoral thesis, KTH, Materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96285.
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The complete and accurate thermodynamic and kinetic description of any systemis crucialfor understanding and predicting its properties. A particular interest is in systemsthat are used for some practical applications and have to be constantly improved usingmodification of their composition and structure. This task can be quite accuratelysolved at a fundamental level by density functional theory methods. Thesemethods areapplied to two practically important systems Fe-Cr and TiC-ZrC.The elastic properties of pure iron and substitutionally disordered Fe-Cr alloy are investigatedas a function of temperature and concentration using first-principles electronicstructurecalculations by the exact muffin-tin orbitals method. The temperature effectson the elastic properties are included via the electronic, magnetic, and lattice expansioncontributions. It is shown that the degree of magnetic order in both pure iron andFe90Cr10 alloy mainly determines the dramatic change of the elastic anisotropy of thesematerials at elevated temperatures. A peculiarity in the concentration dependence ofthe elastic constants in Fe-rich alloys is demonstrated and related to a change in theFermi surface topology.A thermodynamic model for the magnetic alloys is developed from first principles andapplied to the calculation of bcc Fe-Cr phase diagram. Various contributions to the freeenergy (magnetic, electronic, and phonon) are estimated and included in the model. Inparticular, it is found that magnetic short range order effects are important just abovethe Curie temperature. The model is applied for calculating phase equilibria in disorderedbcc Fe-Cr alloys. Model calculations reproduce a feature known as a Nishizawahorn for the Fe-rich high-temperature part of the phase diagram.The investigation of the TiC-ZrC system includes a detailed study of the defect formationenergies and migration barriers of point defects and defect complexes involvedin the diffusion process. It is found, using ab initio atomistic simulations of vacancymediateddiffusion processes in TiC and ZrC, that a special self-diffusion mechanism isoperative for metal atom diffusion in sub-stoichiometric carbides. It involves a noveltype of a stable point defect, a metal vacancy ”dressed” in a shell of carbon vacancies.It is shown that this vacancy cluster is strongly bound and can propagate through thelattice without dissociating.QC 20120604
HERO-M
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Al-Badairy, Hameed Hussein S. "The mechanical and chemical failure of alumina scales formed on Fe-Cr-Al based alloys". Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367056.
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Weber, Johann Karl Richard. "Oxidation of Fe Cr Al alloys in simulated coal gasifier atmospheres at 850-1050°C". Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46905.
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Unfried, Silgado Jimy. "Mecanismo de fratura por queda de ductilidade em ligas Ni-Cr-Fe". [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263356.
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Orientador: Antonio José Ramírez LondoñoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: A fratura por queda de ductilidade (FQD) é um tipo de falha que ocorre em temperatura elevada e que afeta adversamente diversos materiais metálicos com estrutura cristalina cúbica de faces centradas (CFC), tais como, ligas de Níquel, Cobre e aços inoxidáveis. Na FQD é observada uma forte redução da ductilidade e a ocorrência de fratura intergranular no intervalo de temperatura homologa entre 0,4 e 0,8, e sob aplicação de esforços de tensão. Diversos autores têm proposto alguns fenômenos metalúrgicos, tais como o escorregamento ao longo dos contornos de grão e a precipitação de carbonitretos e carbonetos, como fatores que influenciam o comportamento da FQD em estrutura bruta de solidificação de ligas de Níquel. Não obstante, o mecanismo fundamental operante neste tipo de fratura ainda não está totalmente esclarecido. Neste trabalho é estudado o mecanismo operante na FQD em função do papel da precipitação de carbonitretos e das características microestruturais na estrutura bruta de solidificação de ligas Ni-Cr-Fe endurecidas por solução sólida. Foram fabricadas e avaliadas cinco ligas experimentais baseadas na composição da liga 690 com e sem adições de Nb, Mo e Hf, as quais foram projetadas com o suporte do método Calphad. A avaliação da FQD foi realizada a través da aplicação iterativa de técnicas de caracterização baseadas em microscopia eletrônica, combinada com a determinação experimental da energia de falha de empilhamento (EFE) usando radiação sincrotron e o uso de ensaio termomecânico in situ em temperatura elevada acoplado a um microscópio eletrônico de varredura (MEV), cujos resultados permitiram realizar mapeamento da deformação a partir de imagens digitais. O teste in situ facilitou o acompanhamento, em tempo real, do fenômeno de FQD dentro do intervalo de temperaturas entre 500 °C e 1000 °C, evidenciando a ocorrência de escorregamento ao longo dos contornos de grão, o que por sua vez permitiu a identificação das etapas do fenômeno com suas respectivas características. Nas ligas experimentais com adições de Nb e Hf foram obtidos contornos de grão fortemente ondulados devido à alta freqüência de precipitados primários intergranulares finos. A adição de Mo nas ligas experimentais juntamente com as adições de Nb e Hf contribuíram para uma forte diminuição da EFE. Os contornos de grão ondulados foram relacionados com o bloqueio mecânico do escorregamento que ocorre ao longo dos mesmos, como sugerido por diversos autores. A presença de Mo na rede cristalina e a baixa EFE contribuíram na restrição da mobilidade de discordâncias em temperaturas elevadas. As características anteriores foram relacionadas com o aumento da resistência a FQD. Finalmente, baseado na evidencia experimental obtida neste trabalho é proposto um mecanismo fundamental de ocorrência da FQD em estruturas brutas de solidificação por soldagem de ligas Ni-Cr-Fe similar ao mecanismo de fluência sem domínio da difusão com escorregamento ao longo dos contornos de grão proposto por Rachinger.
Abstract: Ductility-dip cracking (DDC) is a high temperature fracture phenomenon, which affects several face centered cubic (FCC) metallic materials, such as Nickel alloys, Copper alloys, and stainless steels. DDC is observed as a drastic reduction of ductility that leads to intergranular fracture at homologous temperature range between 0,4 and 0,8 under tensile stress. Diverse theories related to the grain boundary sliding and to carbides and carbonitrides precipitation were proposed to describe DDC behavior in Ni-alloys; however, the fundamental mechanism of DDC is not clear yet. In this work is investigated the fundamental mechanism of DDC, as well as the role of carbonitride precipitates and metallurgical characteristics on this phenomenon in aswelded solid-solution strengthened Ni-Cr-Fe alloys. Experimental alloys were designed by means of Calphad methodology using the alloy 690 chemical composition as the start point. Five compositions with Nb, Mo and Hf additions were subsequently fabricated and evaluated. The DDC evaluation was performed using electron microscopy characterization techniques, experimental measurements of stacking fault energy (SFE) using synchrotron radiation, and a scanning electron microscopy thermo-mechanical in situ test that allows a strain mapping from digital images. The in situ test has allowed obtaining at real time information about of DDC phenomenon on the temperature range between 500 °C and 1000 °C. Evidences of grain boundary sliding (GBS) were obtained through high temperature experiments, consequently allowing the recognition of DDC stages characteristics. Wavy grain boundaries were obtained in Ni-Cr-Fe alloys with Nb and Hf additions due to the high frequency and homogeneous distribution of fine intergranular primary precipitates. Mo, Nb, and Hf additions contributed for a perceptible SFE reduction. Several authors suggested that wavy grain boundaries block GBS, while the Mo presence in the crystal lattice leads to SFE reduction, which is related to the restriction of dislocations mobility at high temperature and to the increase of DDC resistance. Finally, a new fundamental mechanism of DDC is proposed based on experimental evidences for as-welded structures of Ni-Cr-Fe alloys, which is similar to the creep mechanism without diffusion, involving grain boundary sliding mechanism proposed by Rachinger.
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica
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Wang, Haijuan. "Investigations on the Oxidation of Iron-chromium and Iron-vanadium Molten Alloys". Doctoral thesis, KTH, Materialens processvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12955.
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With the progress of high alloy steelmaking processes, it is essential to minimize the loss of valuable metals, like chromium and vanadium during the decarburization process, from both economic as well as environmental view points. One unique technique to realize this aim, used in the present work, is the decarburization of high alloy steel grades using oxygen with CO2 in order to reduce the partial pressure of oxygen. In the present work, the investigation on the oxidation of iron-chromium and iron-vanadium molten alloys under CO2-O2 mixtures was carried out and presented in this dissertation. For oxidation study on Fe-Cr molten alloy with CO2-O2 mixtures, on the basis of thermodynamic analysis, energy balance calculation and modeling results, experimental validation in laboratory was carried out, and later on, the oxidation kinetics of Fe-Cr and Fe-Cr-C melts under controlled partial pressure of oxygen was investigated. Thermodynamics calculation and energy balance estimation demonstrated that, it is possible to use CO2 or CO2-O2 mixtures as decarburizers during EAF process and high initial carbon contents in the steel can be adopted at the beginning in order to reduce the cost. A generic model has been developed to describe the overall process kinetics prevailing in metallurgical reactors containing liquid metal and gas bubbles. This model is general and can be extended further to consider any gas liquid reactions in any chemical engineering reactor, and especially the metallurgical ones, like AOD. In the present dissertation, the model is applied in predicting the evolution of Cr and C contents in a Fe-C-Cr melt during injection of different O2-CO2 mixtures. The related simulation results illustrated that CO2 is efficient in Cr retention. In order to verify the modeling results, 1kg induction furnace experiments were carried out in the present laboratory. The results indicated that the predictions of the model are in good agreement with the experimental results. Meanwhile, the experimental results indicated that the Cr-losses can be significantly lowered by replacing the oxygen with CO2 in the injected gas, specifically for Fe-Cr-C melts with carbon levels higher than about 0.8 mass%. Subsequently, the oxidation kinetics of Fe-Cr and Fe-Cr-C melts was investigated under different CO2-O2 mixtures. It is indicated that, the oxidation rate is controlled by the chemical reaction at the initial stage and the reaction rate can be expressed as at the Cr range of 11-21 mass% in the Fe-Cr melt. For oxidation study on Fe-V liquid alloy, the investigation of the oxidation kinetics was carried out under CO2-O2 mixtures, which is followed by the study on thermodynamic properties of vanadium containing slags. During oxidation of Fe-V melt, in the case of alloys with vanadium contents exceeding 10 mass%, there exists an incubation period before the chemical reactions prevail the process. In addition, the ‘incubation time’ increased with the increase of temperature and the vanadium content, whereas it decreased with the increase of oxygen partial pressure in the oxidant gas. High-temperature mass spectrometric method was used to determine the activity of the vanadium oxide in CaO-MgO-Al2O3-SiO2-V2O3 slags, whereas, the oxidation states of vanadium in the CaO-MgO-Al2O3-SiO2-VOxslag system was studied by XANES method. The results indicated that, higher basicities stabilize higher vanadium oxidation state, whereas, higher temperature stabilizes lower vanadium oxidation state. The present work, which was carried out within the ECO-STEELMAKING project funded by MISTRA via Jernkontoret is expected to lead to implementation of some modifications in high alloy steel production based on fundamental concepts towards more environment-friendly steel processing.QC20100628
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Olsson, Pär. "Modelling of Formation and Evolution of Defects and Precipitates in Fe-Cr Alloys of Reactor Relevance". Doctoral thesis, Uppsala University, Department of Neutron Research, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6014.
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Fe-Cr alloys form the basis of many industrially important steels. Due to their excellent resistance to radiation induced swelling, ferritic steels are expected to be used for critical structural components in advanced nuclear systems, such as fast breeder reactors, accelerator driven systems and fusion reactors. In this thesis project, theoretical modelling of bulk properties of Fe-Cr alloys has been performed for a wide range of phenomena. Electronic structure calculations, based on density functional theory, have been used to determine equilibrium properties for different magnetic states of the alloy. Ferromagnetic alloys of low Cr concentration (<10% Cr) are anomalously stable, which is related to the variation in sign of the mixing enthalpy which was predicted for the first time in this work. This finding is in agreement with experimental evidence of long range ordering in Fe-Cr alloys with low Cr concentration, as well as the observed phase separation for compositions with higher Cr content.
The character of the interaction of point defects with solute Cr atoms in an iron matrix was investigated ab initio. It was found that due to magnetic interactions, interstitial defects are bound by Cr atoms in bulk iron. Vacancies, on the other hand, interact only weakly with Cr. These results may offer qualitative explanations to the observed concentration dependence of radiation induced swelling in Fe-Cr model alloys.
The ab initio predictions inspired an effort to develop an interatomic alloy potential capable of reproducing both the thermodynamic bulk behaviour of the alloy, such as the mixing enthalpy, and the point defect interactions, in order to perform large scale atomistic and stochastic simulations on scales out of reach for density functional theory. A two-band extension of the embedded atom method of interatomic potentials was developed in order to model ferromagnetic Fe-Cr alloys of arbitrary composition. Kinetic Monte-Carlo simulations of thermal aging, using this two-band potential, reproduce the experimentally measured formation and evolution of solute precipitation as a function of concentration for temperatures relevant to structural materials in nuclear reactors.
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Clauß, Arno Rainer [Verfasser]. "Nitriding of Fe-Cr-Al alloys : nitride precipitation and phase transformations / vorgelegt von Arno Rainer Clauß". Stuttgart : Max-Planck-Inst. für Metallforschung, 2008. http://d-nb.info/995395918/34.
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Olsson, Pär. "Modelling of formation and evolution of defects and precipitates in Fe-Cr alloys of reactor relevance /". Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6014.
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Stallybrass, Charles. "The precipitation behaviour and mechanical properties of novel Fe Al Ni Cr alloys with coherent precipitates". Aachen Shaker, 2007. http://d-nb.info/987862510/04.
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Zhou, Jing. "An Atom-Probe Tomography Study of Phase Separation in Fe-Cr Based Steels". Doctoral thesis, KTH, Metallografi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-150796.
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Stainless steels are very important engineering materials in a variety of applications such as in the food industry and nuclear power plants due to their combination of good mechanical properties and high corrosion resistance. However, ferrite-containing stainless steels are sensitive to the so-called ‘475°C embrittlement’, which is induced by phase separation of the ferrite phase, where it decomposes into Fe-rich ferrite (α) and Cr-rich ferrite (α'). The phase separation is accompanied with a severe loss of toughness. Therefore, the upper service temperature of ferrite-containing stainless steels in industrial applications has been limited to around 250°. In the present work, Fe-Cr based steels were mainly investigated by atom probe tomography. A new method based on the radial distribution function (RDF) was proposed to quantitatively evaluate both the wavelength and amplitude of phase separation in Fe-Cr alloys from the atom probe tomography data. Moreover, a simplified equation was derived to calculate the amplitude of phase separation. The wavelength and amplitude was compared with evaluations using the auto-correlation function (ACF) and Langer-Bar-on-Miller (LBM) method, respectively. The results show that the commonly used LBM method underestimates the amplitude of phase separation and the wavelengths obtained by RDF shows a good exponential relation with aging time which is expected from the theory. The RDF is also an effective method in detecting the phenomena of clustering and elemental partitioning. Furthermore, atom probe tomography and the developed quantitative analysis method have been applied to investigate the influence of different factors on the phase separation in Fe-Cr based alloys by the help of mainly mechanical property tests and atom probe tomography analysis. The study shows that: (1) the external tensile stress during aging enhances the phase separation in ferrite. (2) Phase separation in weld bead metals decomposes more rapidly than both the heat-affected-zone metals and the base metals mainly due to the high density of dislocations in the welding bead metals which could facilitate the diffusion. (3) The results show that Ni and Mn can enhance the phase separation comparing to the binary Fe-Cr alloy whereas Cu forms clusters during aging. (4) Initial clustering of Cr atoms was found after homogenization. Two factors, namely, clustering of Cr above the miscibility gap and clustering during quenching was suggested as the two responsible mechanisms. (5) The homogenization temperatures significantly influence the evolution of phase separation in Fe-46.5at.%Cr.QC 20140910
Spinodal Project
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Heintze, Cornelia. "Einfluss der Bestrahlung mit energiereichen Teilchen auf die Härte von Fe-Cr-Legierungen". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-120166.
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Ferritisch/martensitische Cr-Stähle und deren oxiddispersionsverfestigte Varianten gehören zu den potenziellen Konstruktionswerkstoffen für Komponenten zukünftiger kerntechnischer Einrichtungen, wie z. B. Fusionsreaktoren und Spaltreaktoren der IV. Generation, die Strahlungsfeldern mit hohem Neutronenfluss ausgesetzt sind. Ein Hauptproblem dieser Materialgruppen ist das Auftreten des Spröd-duktil-Übergangs und dessen maßgeblich durch die Strahlenhärtung verursachte Verschiebung zu höheren Temperaturen.
In der vorliegenden Arbeit wird das Bestrahlungsverhalten von binären Fe-Cr-Modelllegierungen untersucht, die ein vereinfachtes Modell für ferritisch/martensitische Cr-Stähle darstellen. Dabei werden Bestrahlungen mit Eisenionen zur Simulation der durch Neutronen hervorgerufenen Schädigung verwendet. Die auf wenige Mikrometer begrenzte Eindringtiefe der Ionen macht es erforderlich, dass für dünne Schichten geeignete Charakterisierungsmethoden eingesetzt werden. Im Rahmen dieser Arbeit sind das Nanohärtemessungen und Transmissionselektronenmikroskopie (TEM).
Im Ergebnis liegen die bestrahlungsinduzierte Härteänderung der Schicht in Abhängigkeit von Chromgehalt, Bestrahlungsfluenz und –temperatur sowie, für ausgewählte Zustände, quantitative TEM-Analysen vor. Zusammen mit begleitenden Ergebnissen von Neutronenkleinwinkelstreuexperimenten an neutronenbestrahlten Proben der gleichen Werkstoffe ermöglichen sie die Identifizierung von bestrahlungsinduzierten Versetzungsringen und nm-großen α’-Ausscheidungen als Quellen der Strahlenhärtung. Im Rahmen eines vereinfachten Modells, das auf Orowan zurückgeht, werden die Hindernisstärken dieser Gitterbaufehler für das Gleiten von Versetzungen abgeschätzt.
Darauf aufbauend erfolgt ausblickartig eine Erweiterung des Untersuchungsgegenstands auf komplexere Situationen hinsichtlich der Bestrahlungsbedingungen und des Werkstoffs. Durch das Einbeziehen simultaner und sequentieller Bestrahlungen mit Eisen- und Heliumionen kann gezeigt werden, dass der Effekt von Helium auf die Strahlenhärtung von der Bestrahlungsreihenfolge abhängt und dass der simultane Eintrag fusionsrelevanter Mengen von Helium zu einer Verstärkung der Strahlenhärtung führt, die auf einem synergistischen Effekt beruht. Für Cr-Stähle mit 9 % Cr und deren oxiddispersionsverfestigte Varianten wird kein grundlegend anderes Bestrahlungsverhalten beobachtet als für binäres Fe-9at%Cr. Es gibt jedoch Hinweise, dass Oxid-dispersionsverfestigung die Strahlenhärtung unter bestimmten Bedingungen reduzieren kann.
Im Ergebnis der Arbeit zeigt sich, dass Ionenbestrahlungen in Kombination mit Nanohärtemessungen zu einem vertiefenden Verständnis der Strahlenhärtung in Werkstoffen auf Fe-Cr-Basis sowie zu einer effektiven Materialvorauswahl beitragen können. Voraussetzung ist, dass der Eindruckgrößeneffekt und der Substrateffekt auf geeignete Weise in Rechnung gestellt werden.
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Stallybrass, Charles [Verfasser]. "The precipitation behaviour and mechanical properties of novel Fe-Al-Ni-Cr alloys with coherent precipitates / Charles Stallybrass". Aachen : Shaker, 2008. http://d-nb.info/1161313362/34.
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Marques, Daniel Cirillo. "Estudo da influencia do teor de niquel na usinabilidade de ligas Fe-Cr-Ni". [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264200.
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Orientador: Anselmo Eduardo DinizDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: O objetivo deste trabalho foi estudar a influência do teor de níquel de ligas FeCrNi na vida da ferramenta de metal duro em processo de torneamento em acabamento. Para este estudo foram preparadas ligas com composição básica 18%Cr-0,01%C-0,2%Si-0,4%Mn e com teores de níquel variados (0, 10, 20, 30, 40, 50 e 60%). A medida que o teor de níquel subia, o teor de ferro diminuía na mesma proporção. Os ensaios foram realizados com pastilhas de metal duro classe M15 revestidas com TiC/Al2O3/TiN. Todos os materiais foram usinados nas mesmas condições (vc = 230 m/min, ap = 0,6 mm e f = 0,1 mm/volta), garantindo assim, como única fonte de variação, o teor de níquel. Os resultados mostram que a vida da ferramenta diminui com o aumento do teor de níquel e que o principal mecanismo de desgaste da ferramenta é a adesão e arrancamento de partículas da ferramenta. Uma exceção se deu com o material com 30% de níquel, que apesar de apresentar o mesmo mecanismo de desgaste, mostrouse mais fácil de usinar, gerando maior tempo de vida da ferramenta
Abstract: The aim of this work was to study the influence of nickel content in FeCrNi alloys on the coated cemented carbide tool life during the finish turning process. For this purpose 18%Cr-0,01%C-0,2%Si-0,4%Mn base composition and variable nickel content (0, 10, 20, 30, 40, 50 and 60 weight %) alloys were prepared. As the nickel content increased, the iron content decreased in the same proportion. Tests were carried out with coated cemented carbide inserts, M15 class with TiC/Al2O3/TiN coating. All alloys were machined on the same cutting conditions (vc = 230 m/min, ap = 0,6 mm and f = 0,1 mm/rev), in order to set nickel content as the only input variable. Results indicate that tool life decreases with the growth of nickel content, and the mainly tool wear mechanism is attrition. An exception was the material with 30% of nickel, that presented the same tool wear mechanism but showed out higher machinability, allowing longer tool life
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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Costa, Davide. "Modelling the thermal ageing evolution of Fe-Cr alloys using a lattice kinetic Monte Carlo approach based on DFT calculations". Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10037/document.
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Cette thèse aborde l'étude du vieillissement thermique du système Fe-Cr. Nous avons étudié le mécanisme de diffusion de la lacune dans le cadre de la théorie de la fonctionnelle de la densité (Density Functional Theory - DFT) et examiné la capacité d'un potentiel empirique de la classe EAM (Embedded Atom Method) à reproduire les résultats DFT. Nous avons montré que l'énergie de migration de la lacune dépend fortement de l'environnement atomique du point de col où les interactions chrome-chrome et chrome-lacune déterminent en partie l’énergie de point de col. Nous avons proposé trois approches pour la paramétrisation d'un modèle Monte Carlo Cinétique (MCC) atomique : l’une entièrement basée sur le potentiel EAM, les autres partiellement basées sur nos calculs DFT. Les simulations par MCC du vieillissement thermique des alliages Fe-20% at. Cr et Fe-25% at. Cr à 773 K montrent la formation de précipités riches en chrome dont la croissance avec le temps suit une loi de puissance avec un exposant 1/3, en accord avec la théorie de Lifshitz-Slyozov-Wagner. La paramétrisation des simulations par MCC entièrement basée sur le potentiel EAM prédit une taille moyenne des précipités supérieure à celle observée expérimentalement, alors que cette dernière est sous-estimée par les paramétrisations partiellement basées sur nos calculs DFT. Ce désaccord semble avoir une origine cinétique plutôt que thermodynamique. La composition de la phase riche en chrome varie au cours de la séparation de phase, indiquant ainsi que la démixtion se produit par nucléation non-classique ou par décomposition spinodale. Des précipités interconnectés sont plus susceptibles de se former dans le système Fe-25% at. Cr plutôt que dans l’alliage Fe-20% at. Cr suggérant ainsi que, lorsque la concentration en soluté augmente, le mécanisme de démixtion se rapproche de la décomposition spinodaleIn this thesis, we address the study of the microstrucutre evolution of the Fe-Cr system under thermal ageing. The vacancy diffusion mechanism was investigated in the framework of the density functional theory (DFT) and the capability of a recently developed embedded atom method (EAM) empirical cohesive model to reproduce the DFT results was examined. We have shown that the vacancy migration energy strongly depends on the saddle point atomic environment where the chromium-chromium and the chromium-vacancy interactions partially determine the saddle point energy. We proposed three approaches for the parameterisation of an atomistic kinetic Monte Carlo (AKMC) model: one fully based on the EAM potential, the others partially based on our DFT calculations. The AKMC simulations of the thermal ageing of the Fe-20 at.%Cr and Fe-25 at.%Cr alloys at 773 K show the formation of chromium-rich precipitates whose growth with time follows a power law with exponent 1/3. This is consistent with the Lifshitz-Slyozov-Wagner theory of coarsening. The AKMC parameterisation fully based on the EAM potential predicts a mean precipitate size higher than the experimentally observed one, whereas the parameterisations partially based on our DFT calculations underestimate it. This disagreement seems to have a kinetic rather than thermodynamic origin. The composition of the precipitating phase varies during the phase separation thus indicating that the unmixing is driven by either a non-classical nucleation or a spinodal decomposition. Interconnected precipitates are more likely to form in the Fe-25 at.%Cr alloy than in the Fe-20 at.%Cr thus suggesting that, as the solute concentration increases, the spinodal decomposition is more likely to occur
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Cardoso, Amanda da Silva. "Estudo da corrosÃo de ligas Fe-Cr-Mo em Ãgua artificial de tanque de armazenamento de petrÃleo saturada com CO2". Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=8477.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorConselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
O objetivo deste trabalho foi avaliar a influÃncia da porcentagem em massa de Mo em ligas Fe-Cr-Mo frente à corrosÃo por CO2 em Ãgua artificial de tanque de armazenamento de petrÃleo e propor uma liga experimental para ser usada em dutos suscetÃveis a esse tipo de corrosÃo. Foram estudados o aÃo carbono 1020, para comparaÃÃo, e dois tipos de ligas Fe-Cr-Mo, uma comercial, denominada P9 (Fe-9Cr-1Mo); e uma liga experimental, E (Fe-9Cr-5Mo). Foram feitas medidas de PLP com tempo de Eca de 1 h. As curvas mostraram que, no aÃo 1020, ocorre apenas a dissoluÃÃo do Fe, enquanto que, com o aumento da porcentagem de Mo, ocorre passivaÃÃo. O monitoramento da corrosÃo foi feito por espectroscopia de impedÃncia eletroquÃmica, ao longo de 168 h de imersÃo. Os diagramas de Nyquist mostraram que o aumento na quantidade de Mo aumenta a impedÃncia das ligas estudadas. Jà as representaÃÃes de Bode mostraram que hà apenas um processo na corrosÃo no aÃo 1020, enquanto que hà dois para as ligas P9 e E. A caracterizaÃÃo da superfÃcie foi feita por MEV. A distribuiÃÃo dos produtos de corrosÃo foi homogÃnea no aÃo 1020 e heterogÃnea nas demais ligas. A identificaÃÃo dos produtos de corrosÃo foi feita por espectroscopia RAMAN, mostrando que houve a formaÃÃo de produtos de corrosÃo protetores apenas para as ligas Fe-Cr-Mo e que apenas a liga E apresentou produtos contendo Mo. Isso està em acordo com os resultados obtidos nas curvas de polarizaÃÃo e nos diagramas de impedÃncia, uma vez que o Mo pode estabilizar filmes de passivaÃÃo. Assim, a liga experimental E pode ser usada em substituiÃÃo à liga comercial P9 em plantas de exploraÃÃo de petrÃleo suscetÃveis a corrosÃo por CO2.
The objective of this work was to evaluate the influence of the percentage in mass of Mo in Fe-Cr-Mo alloys against CO2 corrosion in artificial water of oil storage tank and to propose an experimental alloy to be used in susceptible to this kind of corrosion pipes. They had been studied the 1020 carbon steel, for comparison, and two types of Fe-Cr-Mo alloys, one advertising, called P9 (Fe-9Cr-1Mo); and one experimental alloy, E (Fe-9Cr-5Mo). They had been made measurements of LSP with time of Eoc of 1 h. The curves had shown that, in 1020 steel, the dissolution of Fe occurs only, whereas, with the increase of the percentage of Mo, occurs passivation. Monitoring of the corrosion was made by electrochemical impedance spectroscopy, throughout 168 h of immersion. Nyquist diagrams had shown that the increase of Mo content increased the impedance of the studied alloys. Although, the Bode representations showed that there is only one process in the corrosion of 1020 steel, while there are two ones for P9 and E alloys. The characterization of the surface was made by SEM. The distribution of the corrosion products was homogeneous in the 1020 steel and heterogeneous one in the other alloys. The identification of the corrosion products was made by RAMAN spectroscopy, showing that there was protective corrosion products formation only to Fe-Cr-Mo alloys and that only the E alloy presented Mo-containing products. This is in agreement with the results obtained in polarization curves and in impedance diagrams, once Mo can stabilizes passivation films. So, experimental E alloy can be used in substitution of P9 alloy in oil exploration plants susceptible to CO2 corrosion.
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Kneeshaw, Jonathan Andrew. "The corrosion behavior of Fe-Cr-Ni alloys in complex high temperature gaseous atmospheres containing the reactants oxygen, sulphur and carbon". Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/14610.
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A systematic in-depth study has been undertaken to establish the corrosion mechanism of a Model 25Cr-35Ni-Fe alloy and four commercial alloys HP40Nb, AISI314, HP40Al and Alloy 800H in low oxygen, high sulphur and carbon containing environments typically found in coal gasification and fluidised bed combustion processes. A review of present knowledge of corrosion processes in purely oxidizing, sulphidizing and carburizing environments and multiple reactant carburizing/ oxidizing, carburizing/sulphizing and oxidizing/sulphidizing environments is given. The experimental programme was designed to establish the role of sulphur on the corrosion process by studying corrosion mechanisms in a sulphurfree H2-7%C0-1.5%H2o gas, a low sulphur H2-7%C0-1.5%H20-0.2%H 2 S gas (pS2_8= 10 bar), and a high sulphur H 2 -7%C0-1.5%H 2 0-0.6%H 2 S gas (pS = lO bar) at 800'C. All_21j_hree environments had a constant partiaf pressure of oxygen (po2 = 10 bar) and carbon activity (ac = 0.3). In the sulphur-free gas the Model alloy formed a thin uniform cr 2 o 3 layer which grew at a constant parabolic rate throughout the exposure period of 0 - 5000 hours. Surface working increased the growth rate and thickness of the Cr 2 o 3 layer but created a large number of cracks and pores which allowed carbon containing gaseous species to diffuse through the oxide to form carbide precipitates in the alloy substrata. Alloying additions of Si promoted the formation of an inner SiO layer which reduced the corrosion rate by cutting off the outward diffusion of Cr, Mn and Fe. Alloying additions of Mn promoted the formation of an additional outer (Mn, Fe )Cr 2o 4 layer. The 3. 5% Al content of the HP40Al was insufficient to form a complete Al 2 o3 layer. Alloy 800H was susceptible to localised internal oxidation. Adding a low level of sulphur (0.2% H 2 S) to the gas increased the corrosion rate of the Model alloy in the 1nitial stages. This rate gradually slowed down before becoming parabolic after 1000 - 2000 hours. This was due to the nucleation of sulphides in addition to oxides. The oxides and sulphides grew side by side until the oxides overgrew the sulphides to form a complete Cr 2o3 layer which cut off further ingress of sulphur from the gas. The entrapped sulphides promoted localized thickening of the oxide layer. Eventually the sulphur redistributed from the sulphides in the scale to internal sulphide precipitates in the alloy with the corrosion rate returning to that of the sulphur-fre,e gas for the rest of the exposure period (5000 hours total). In the commercial alloys the internal sulphide precipitates prevented the inner Si02 layer becoming complete. Sulphur doped the (Mn, Fe) Cr 2 0 4 outer layer ana the intermediate Cr 2o3 layer formed from the spinal layer, increasing the number of cation . vacancies and the growth rate of the scale. These factors caused a massive Cr depletion of the alloy substrata after several thousand hours. The internal carbides became unstable which led to a massive amount of internal attack and a dramatic increase (breakaway) in the corrosion rate. Due to its thickness and the presence of Si02 inner layer the external scale became susceptible to spallation. If this occurred the oxides and sulphides nucleated on the alloy surface again but sulphides. protective alloy. insufficient Cr was available for the oxides to overgrow the The sulphides therefore grew to form a fast growing nonsulphide scale which soon led to catastrophic failure of the Increasing the level of sulphur in the gas to 0.6% H2S caused oxides and sulphides to nucleate on the surface, but in this case the sulphides overgrew the oxides to form thick fast growing non-protective sulphide scales on all the alloys.
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Ulmer, Ulrich [Verfasser] y R. [Akademischer Betreuer] Dittmeyer. "Effects of Impurities on the Performance and Cost of V-Fe-Cr-Ti-based Solid Solution Alloys / Ulrich Ulmer. Betreuer: R. Dittmeyer". Karlsruhe : KIT-Bibliothek, 2016. http://d-nb.info/1097380890/34.
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Dong, Chuang. "Structure et formation des quasicristaux et des phases cristallines approximantes dans les alliages Ti-Fe, Al-Cu-Fe(-Cr), Al-Cu-Co(-Si) et Al-Pd-Mn". Vandoeuvre-les-Nancy, INPL, 1991. http://docnum.univ-lorraine.fr/public/INPL_T_1991_DONG_C.pdf.
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Nous avons analysé par microscopie électronique à transmission et par diffraction des neutrons les alliages quasicristallins suivants: Ti2Fe, Al65Cu20Fe15, Al71Pd19Mn10, Al65Cu20Fe10Cr5, Al65Cu17,5 et Al63Cu17,5Si2. Toutes ces études abordent deux aspects différents de ces alliages : les phases quasicristallines et leurs approximants cristallins. Dans le premier aspect, nous avons étudié la structure et la formation des phases icosaédriques Ti-Fe, Al-Cu-Fe et Al-Pd-Mn. Les mécanismes de croissance ont été identifiés. Les vitesses de croissance de ces quasicristaux sont très faibles par rapport à celles des cristaux. En ce qui concerne le deuxième aspect, nous nous sommes attachés à l'étude des approximants de la phase décagonale dans les alliages Al65Cu20Fe10Cr5 et Al63Cu17,5Co17,5Si2. Nous avons pu relier la phase décagonale à ses approximants en mettant en évidence les mêmes types d'unités structurales. Nous avons aussi mis l'accent sur la phase de type CsCl qui peut être la structure de base pour toutes les structures quasicristallines et cristallines étudiées dans ce travail
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WANG, CHAO-ZHENG y 王朝正. "High temperature oxidation of Fe-Mn-Al-Cr alloys". Thesis, 1988. http://ndltd.ncl.edu.tw/handle/56291925298037407643.
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