Relevant bibliographies by topics / M23C6

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  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers

Academic literature on the topic 'M23C6'

Author: Grafiati
Published: 4 June 2021
Last updated: 29 January 2023

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Journal articles on the topic "M23C6"

1

Zhao, Hongchang, Zixi Wang, Xi Han, and Mingjia Wang. "Effect of Long-Term Aging on the Microstructural Evolution in a P91 Steel." Materials 15, no. 8 (April 13, 2022): 2847. http://dx.doi.org/10.3390/ma15082847.

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The precipitation and growth mechanism of the Laves phase and the coarsening behaviors of Laves phase, M23C6 and MX carbonitrides have been emphatically investigated in P91 steel at 625 °C under different aging conditions. After long-term aging at 625 °C (>1500 h), it was observed that the Laves phase grew rapidly in the region near the M23C6 carbide once precipitated, and further gradually completed the engulfment process until the M23C6 carbide particles disappeared. Furthermore, a new crystallographic orientation relationship between M23C6 carbides and Laves phase has been observed at 625 °C for 5000 h, which is {0001}Laves∥{111}M23C6, <112¯1>Laves∥ <011>M23C6. The coarsening behaviors of Laves phase, M23C6 carbides and MX carbonitrides have been emphatically investigated, conforming to the existing ripening model of multicomponent alloys. The coarsening rates for the Laves phase, M23C6 and MX have values of ~32.2 (≥5000 h), 5.3 and 0.6 nm/h1/3, respectively.
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Kim, Hong-Pyo, Yun-Min Park, Hyoung-Min Jang, Sang-Yeob Lim, Min-Jae Choi, Sung-Woo Kim, Dong-Jin Kim, Seong-Sik Hwang, and Yun-Soo Lim. "Early-Stage M23C6 Morphology at the Phase Boundary in Type 304L Austenitic Stainless Steel Containing δ Ferrite." Metals 12, no. 11 (October 24, 2022): 1794. http://dx.doi.org/10.3390/met12111794.

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The early-stage M23C6 morphology at the phase boundary between austenite and δ ferrite grain in Type 304L austenitic stainless steel was investigated with transmission electron microscopy (TEM). The M23C6 has coherency with austenite grains at phase boundary. The phase boundary between the M23C6 and austenite grains has curved appearance. The curved phase boundary might be a faceted interface composed of (111) plane and the other low-index planes on the atomic scale. The M23C6 morphology at the phase boundary was identified to be a complex pyramid-like shape that has {111}, {110} and {100} interfaces. The slight deviation in the angle measured between edges of carbide in the TEM images from that calculated between edges expected from the M23C6 morphology might be attributed to multilayer growth in the interior region of the M23C6 face.
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Song, Young-Gy, Jun-Seok Oh, Baig-Gyu Choi, Chang-Yong Jo, and Je-Hyun Lee. "Effects of Primarily Solidified Dendrite and Thermal Treatments on the M23C6 Precipitation Behavior of High-Chromium White Iron." Metals 11, no. 11 (October 23, 2021): 1690. http://dx.doi.org/10.3390/met11111690.

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The precipitation behavior of M23C6 carbide during thermal treatment of high-Cr white iron with various fractions of primarily solidified dendrite was studied and reviewed. M23C6 precipitation in the primarily solidified dendrite occurred preferentially during conventional heat treatment, whereas it occurred scarcely in the eutectic austenite. The reaction between M7C3 and austenite caused the dissolution of M7C3 into austenite, followed by precipitation of M23C6 along the periphery of eutectic M7C3. Relatively low-temperature thermal treatment (modified heat treatment) led to precipitation of M23C6 particles in the eutectic austenite, which is presumed to be caused by solubility difference depending on temperature.
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Redjaïmia, Abdelkrim, and Antonio Manuel Mateo Garcia. "On the M23C6-Carbide in 2205 Duplex Stainless Steel: An Unexpected (M23C6/Austenite)—Eutectoid in the δ-Ferritic Matrix." Metals 11, no. 9 (August 25, 2021): 1340. http://dx.doi.org/10.3390/met11091340.

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This study is focused on isothermal and anisothermal precipitation of M23C6 carbides from the fully ferritic structure of the (γ + δ) austenitic-ferritic duplex stainless steel X2CrNiMo2253, (2205). During isothermal heat treatments, small particles of K-M23C6 carbide precipitates at the δ/δ grain-boundaries. Their formation precedes γ and σ-phases, by acting as highly potential nucleation sites, confirming the undertaken TEM investigations. Furthermore, anisothermal heat treatment leads to the formation of very fine islands dispersed throughout the fully δ-ferritic matrix. TEM characterization of these islands reveals a particular eutectoid, reminiscent of the well-known (γ-σ)—eutectoid, usually encountered in this kind of steel. TEM and electron microdiffraction techniques were used to determine the crystal structure of the eutectoid constituents: γ-Austenite and K-M23C6 carbides. Based on this characterization, orientation relationships between the two latter phases and the ferritic matrix were derived: cube-on-cube, on one hand, between K-M23C6 and γ-Austenite and Kurdjumov-Sachs, on the other hand, between γ-Austenite and the δ-ferritic matrix. Based on these rational orientation relationships and using group theory (symmetry analysis), the morphology and the only one variant number of K-M23C6 in γ-Austenite have been elucidated and explained. Thermodynamic calculations, based on the commercial software ThermoCalq® (Thermo-Calc Software, Stockholm, Sweden), were carried out to explain the K-M23C6 precipitation and its effect on the other decomposition products of the ferritic matrix, namely γ-Austenite and σ-Sigma phase. For this purpose, the mole fraction evolution of K-M23C6 and σ-phase and the mass percent of all components entering in their composition, have been drawn. A geometrical model, based on the corrugated compact layers instead of lattice planes with the conservation of the site density at the interface plane, has been proposed to explain the transition δ-ferrite ⇒ {γ-Austenite ⇔ K-M23C6}.
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Oh, Jun-Seok, Young-Gy Song, Baig-Gyu Choi, Chalothorn Bhamornsut, Rujeeporn Nakkuntod, Chang-Yong Jo, and Je-Hyun Lee. "Effect of Dendrite Fraction on the M23C6 Precipitation Behavior and the Mechanical Properties of High Cr White Irons." Metals 11, no. 10 (October 3, 2021): 1576. http://dx.doi.org/10.3390/met11101576.

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High Cr white irons with various fractions of primary dendrite have been prepared through the modification of their chemical composition. Increasing C and Cr contents decreased the primary dendrite fraction. Eutectic solidification occurred with the phase fraction ratio of austenite: M7C3 = 2.76:1. The measured primary dendrite fractions were similar to the calculated results. ThermoCalc calculation successfully predicted fractions of M7C3, austenite, and M23C6. Conventional heat treatment at high temperature caused a destabilization of austenite, releasing it’s solute elements to form M23C6 carbide. Precipitation of M23C6 during destabilization preferentially occurred within primary (austenite) dendrite, however, the precipitation scarcely occurred within austenite in eutectic phase. Thus, M23C6 precipitation by destabilization was relatively easy in alloys with a high fraction of primary dendrite.
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Li, Shanlin, Kejian Li, Mengjia Hu, Yao Wu, Zhipeng Cai, and Jiluan Pan. "The Mechanism for HAZ Liquation of Nickel-Based Alloy 617B During Gas Tungsten Arc Welding." Metals 10, no. 1 (January 6, 2020): 94. http://dx.doi.org/10.3390/met10010094.

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The mechanism for HAZ (heat-affected zone) liquation of alloy 617B during gas tungsten arc welding (GTAW) was investigated. Welding thermal simulation work was conducted to investigate the effects of thermal parameters (peak temperature, holding time, and thermal cycle numbers) on M23C6 carbides’ evolutionary behavior in nickel-based alloy 617B. OM (optical microscopy), SEM (scanning electron microscopy), TEM (transmission electron microscopy), and SIMS (secondary ion mass spectrometry) were employed to characterize HAZ carbides. It was found that the constitutional liquation of M23C6 carbides is responsible for HAZ liquation in alloy 617B. Rapid heating meant that solute atoms released from partially dissolved M23C6 carbides did not have enough time to sufficiently diffuse into the matrix, resulting in eutectic reaction M23C6 + γ → liquid in the temperature range from 1250 °C to 1300 °C. In the following cooling process, the liquid phase transformed into γ and M23C6 (or M6C) carbides simultaneously, creating a eutectic microstructure. Subsequent thermal cycles with peak temperature 1100 °C and proper holding time brought about a tempering effect to precipitate fine M23C6 carbides from the Cr supersaturated zone around the eutectic microstructure. Boron was found to be enriched in carbides and was expected to promote HAZ liquation by two mechanisms. No cracking caused by HAZ liquation has been found, indicating that GTAW is a suitable method for joining alloy 617B.
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Igarashi, Masaaki, Koji Moriguchi, Seiichi Muneki, Fujio Abe, and Yasuharu Shirai. "Analysis of Creep Deformation Process of Heat Resistant Steels Using Positron Annihilation Lifetime." Materials Science Forum 561-565 (October 2007): 2233–36. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.2233.

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Creep deformation mechanism of the steels with a different matrix, α (ferrite), α’ (martensite) and γ (austenite), and precipitates such as MX and M23C6 has been analyzed using positron annihilation lifetime measurement. The positron annihilation lifetime has been found to be a very useful tool for evaluating the characteristic creep damage of the steels with different microstructure and the corresponding microstructural evolution during creep deformation. The creep deformation process of the α steel is heterogeneous, while the α’+M23C6 steel exhibits gradual changes in the creep rate in both transient and acceleration creep regions with the largest off-set strain, implying the homogeneous creep deformation. The α’+M23C6+ MX steel is in between the α and α’+M23C6 steels. The homogeneous creep deformation takes place in the γ steel.
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Laigo, Johanne, Franck Tancret, René Le Gall, and Jader Furtado. "EBSD Phase Identification and Modeling of Precipitate Formation in HP Alloys." Advanced Materials Research 15-17 (February 2006): 702–7. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.702.

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Heat-resistant steels of HP series (Fe-25Cr-35Ni) are used as reformer tubes in petrochemical industries. Their composition includes Nb and Ti as strong carbide formers. In the ascast condition, alloys exhibit an austenite matrix with intergranular MC, M23C6 and/or M7C3 eutectic carbides. During exposure at high temperature, phase transformations occur: chromium carbides of M7C3 type transform into the more stable M23C6 type, intragranular M23C6 carbides precipitate, and a silicide, the G-phase (Ni16Nb6Si7), forms due to the instability of MC carbides (NbC). Thermodynamic simulation is of great help for understanding precipitate formation and transformations. Thermo-Calc and Dictra are used to simulate the precipitation of carbides in the austenite matrix during service. However, from an experimental point of view, M23C6 and M7C3 are not easy to distinguish in bulk alloys. Indeed, backscattered scanning electron microscopy does not bring any contrast between the two phases, and energy dispersive spectroscopy (EDS) analysis does not lead to carbon content and consequently to the distinction between M23C6 and M7C3. With transmission electron microscopy (TEM), sample preparation is difficult and the observed area is extremely small. In the present work, HP alloys are investigated by electron backscatter diffraction (EBSD) coupled to EDS. Carbides are identified on the basis of crystal structure, in the bulk, within their microstructural context, and the experimental procedure is both simpler and cheaper than TEM. Precipitates (M23C6, M7C3) could be identified by orientation mapping and single spot analysis.
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Chouksey, Yogendra, and Surya D. Yadav. "Influence of alloying elements on the coarsening coefficients of M23C6 and M2B precipitates in a 10% Cr Belgorod steel." IOP Conference Series: Materials Science and Engineering 1248, no. 1 (July 1, 2022): 012028. http://dx.doi.org/10.1088/1757-899x/1248/1/012028.

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Abstract A 10% Cr steel designed by ‘Belgorod State University’, has been considered in the present work in order to study the effect of alloying elements on the coarsening characteristics of precipitates. The stepped equilibrium diagram was constructed through the CALPHAD approach, employing the ThermoCalc software. The precipitates observed at the temperature of interest, i.e., 650 °C, were M23C6 (M=Cr, Fe), Laves phase, M2B, NbC and TiN. Amongst all the precipitates, M23C6 has the maximum phase fraction, i.e., 0.022. The magnitude of the coarsening coefficients for all the precipitates other than Laves phase, were observed to be of the order of 10-29 m3/s. In case of Laves phase, it was of the order of 10-31 m3/s. The variation of the coarsening coefficients of M23C6 and M2B, with respect to weight percent of alloying elements has been also investigated. It was observed that, with the increase in the weight percent of Co, Nb and W; the coarsening coefficients of M23C6 and M2B decrease. However, with the increase in weight percent of the V, the coarsening coefficients of M23C6 decrease and M2B increase.
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Liu, Yang, Lei Wang, Yu Chen Wang, Hong Yan Liu, Xue Jiao Chen, and Yan Yu. "Effects of Electropulsing Treatment on the Precipitation Behaviour of Grain Boundary Carbides in GH3044 Alloy." Materials Science Forum 654-656 (June 2010): 464–67. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.464.

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The effects of electropulsing treatment on the precipitation behaviour of grain boundary carbides in GH3044 alloy were investigated. The results showed that the initial temperature of precipitation of M23C6 type carbides on grain boundary could be decreased by electropulsing treatment under the condition of high current density of 10.0kA/mm2 with a frequency of 5Hz and pulse width of 15s. The volume percentage of M23C6 type carbide was greatly increased to 274.60% comparing with that of the aging treatment at the same temperature. However, the precipitation of M23C6 type carbide was inhibited by electropulsing treatment under the condition of high frequency of 45Hz with the current density of 2kA/mm2 and pulse width of 15s. The volume percentage of M23C6 type carbide was decreased to 18.81% comparing with that of the aging treatment at the same temperature. It has been found that the diffusion of solute atom in the alloy can be promoted by the electric effect with the electropulsing. As a result, the thermodynamic condition and kinetics of the precipitation of M23C6 type carbide were changed, and both the initial and peak temperatures of precipitation were decreased.
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Dissertations / Theses on the topic "M23C6"

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Ekström, Karin, and Shanar Kordbache. "Equilibrium studies in the Co-Cr-C system : Solubility of Cobalt in M23C6 and M3C2." Thesis, KTH, Materialvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-37914.

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This project concerns cemented carbides and the carbides that are formed when adding chromium. Cemented carbides are composites, often consisting of tungsten-carbide particles embedded in a cobalt-rich matrix, and are because of their extreme hardness used in for example cutting tools and drills. Chromium is sometimes added when making cemented carbides in order to lower the melting point, reduce grain growth and/or increase corrosion resistance. When adding chromium there is a risk of forming unwanted carbides such as M 23C6, M7C3and M3C2. It is therefore of great interest to know the stability of these carbides. The purpose of this work was to investigate the solubility of Co in M23C6 and M3C2by equilibrium studies. The aim was to produce samples equilibrated in the three-phase regions between liquid‐M23C6‐M7C3 and M3C2‐M7C3‐graphite, to study the solubility of Co in M23C6 and M3C2 respectively. Initial studies were performed at Sandvik Mining and Construction (SMC) to determine the compositions of the samples to be produced and temperatures for the heat treatments. The alloys were heat‐treated at 1450⁰C for three days and were thereafter investigated with LOM and XRD. The work was carried out in collaboration with Sandvik Mining and Construction (SMC). It was difficult to analyze the results with XRD since the intensity peaks in the diffractograms are close or overlapping for the M23C6 and M7C3 carbides. The solubility of Co in M23C6 could not be investigated accurately. The M3C2-M7C3‐graphite sample did not reach equilibrium in the three days of heat treatment. The conclusions that can be drawn from this project are that further work, using longer annealing times, has to be done in order to get more knowledge about the Co solubility in M23C6 and M7C3 carbides.
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Guiz, Robin. "Influence d’additions de titane/tungstène et de vanadium sur la précipitation de carbures secondaires au sein d’alliages modèles de type HP." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEM011/document.

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Les alliages de type HP constituent un matériau de choix pour l'élaboration des tubes de vaporeformage et de vapocraquage dans l'industrie pétrochimique. Exposés à des températures comprises entre 700°C et 1000°C sous des pressions gazeuses de plusieurs MPa, leur microstructure initiale associée à une fine précipitation secondaire, intervenant en cours de service, leur confèrent une excellente résistance aux mécanismes de fluage auxquels ils sont sujets. Néanmoins, à terme, la coalescence des précipités conduit à la dégradation rapide des tubes.Les effets de certains éléments d'alliages (V, Ti/W) sur la précipitation secondaire des carbures M23C6 et NbC ont été étudiés au travers de simulations via le logiciel TC-PRISMA. Sur la base de résultats prometteurs en termes d'optimisation des caractéristiques de la précipitation, deux alliages modèles ont été coulés au laboratoire et soumis à divers vieillissements dans la gamme de température correspondant aux conditions de service. Les microstructures de ces alliages ont d'abord été comparées à celle d'un alliage HP industriel de composition standard à l'état brut de coulée. La précipitation secondaire a par la suite été caractérisée au sein des trois alliages dans les différents états vieillis. Les investigations microstructurales ont permis de mettre en avant certains effets bénéfiques d'un ajout de vanadium et d'ajouts combinés de titane et de tungstène sur les caractéristiques de la précipitation secondaire
HP alloys are typically used as steam methane reforming tubes in the petrochemical industry. During service, they are exposed to temperatures between 700°C and 1000°C under gaz pressure of several MPa. Their as-cast microstructure, together with fine in-situ secondary precipitation, provide these alloys with an excellent resistance to creep deformation. Nevertheless, after long-time ageing, coarsening of secondary carbides leads to the weakening of the tubes and therefore to an accelerated damaging.The effects of some alloying elements (V, Ti/W) on secondary precipitation of M23C6 and NbC carbides were investigated through numerical simulations performed with TC-PRISMA software. On the basis of encouraging results in terms of precipitation optimization, two model HP-type alloys were cast at the laboratory and aged in the range of temperatures corresponding to service conditions. As-cast microstructures were first compared with an industrial "standard" alloy. Then, secondary precipitation were characterized for all the alloys and all ageing temperatures. Microstructural investigation highlighted the beneficial effect of vanadium and titanium/tungsten additions on secondary precipitation characteristics
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Maminska, Karolina. "Optimisation microstructurale d’un acier HP pour des applications à haute température." Thesis, Saint-Etienne, EMSE, 2013. http://www.theses.fr/2013EMSE0696/document.

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L’objectif de ce travail est d’améliorer la durée de vie en fluage d’un alliage résistant à haute température. L’alliage étudié, nommé « C », appartient à la classe des aciers austénitiques de type HP utilisés pour la fabrication des tubes de reformage. L’évolution microstructurale de l’alliage « C » a été étudiée dans une vaste gamme de températures, s’étendant de 700 à 1040°C pour des temps de vieillissement allant jusqu’à 1000 h. La caractérisation de ces états vieillis a été réalisée au moyen de la microscopie électronique (MEB-FEG, MET) et de la diffraction des rayons X. L’accent a été mis sur une caractérisation fine de la précipitation secondaire présente Ces résultats ont ensuite été utilisés afin d’identifier les conditions thermiques optimales pour l’affinement de la précipitation en vue d’amélioration du comportement macroscopique de l’alliage. La cinétique de précipitation a été modélisée à l’aide du logiciel PRISMA ThermoCalc. Un bon accord entre la simulation et les mesures expérimentales a pu être obtenu.Dans la gamme de températures étudiée, la précipitation secondaire est majoritairement constituée de deux carbures : M23C6 (M=Cr, Fe) et NbC. En condition de service (980°C), la croissance du M23C6 est rapide. La coalescence des précipités survient dès 200 h de vieillissement. Nous avons prouvé qu’un vieillissement à des températures plus basses (700-750°C) permet d’affiner cette précipitation. De plus, notre étude a montré l’efficacité d’un prétraitement à des températures basses, effectué avant la mise en service du matériau à 980°C. Une nette amélioration de la résistance en fluage dans des essais accélérés a été obtenue pour l’alliage « C » ayant subi le prétraitement cité ci-dessus. Outre l’affinement et le retardement de la coalescence du M23C6, la présence d’une précipitation nanométrique du NbC sur des lignes de dislocations est probablement à l’origine de cet effet
The purpose of this work is to optimise the microstructure of a creep-resistant alloy of the type HP, called “C” (industrial denomination). These austenitic steels are used for the manufacture of reformer tubes. The microstructural evolution of the alloy "C" has been studied in a wide range of temperatures, ranging from 700 to 1040 °C for aging times up to 1000 h. The characterization of these aged states was performed using electron microscopy (FEG-SEM, TEM) and X-ray diffraction, with emphasis on a detailed characterization of this secondary precipitation. This knowledge was then used to identify the optimal thermal conditions for the refinement of precipitation to improve the macroscopic behaviour of the alloy. The precipitation kinetics was modelled using the PRISMA ThermoCalc. A good agreement between simulation and experimental measurements has been obtained.In the studied range of temperature, the secondary precipitation consists mainly of two carbides M23C6 (M = Cr, Fe) and NbC. In the service conditions (980°C), the growth of M23C6 is fast. The coalescence of the precipitates starts after only 200h of aging. Aging at lower temperatures (700-750°C) refines this precipitation. Our study showed the efficacy of pre-treatment of the alloy at low temperatures, before the service of the material at 980°C. In the alloy "C", treated in such conditions, a significant increase in creep resistance was obtained in accelerated testing. In addition to refinement of the secondary precipitation and delaying the effects of coalescence of M23C6, the presence of a nanoscale precipitation of NbC on dislocation lines is probably the origin of this effect
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Li, Letian. "Microstructural evolution in 9 wt.% Cr power plant steels." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/11980.

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High chromium ferritic steels such as Grade 91 and Grade 92 are extensively used in the power plant industry. Components made from these types of steels, including headers, steam pipes and tubes, are required to provide reliable service at high pressures (20-30 MPa) and temperatures (550-610°C) for several decades. However, in order to further improve the thermal efficiency of the power plant, the future operation temperature for the ferritic steels needs to be elevated to 650°C. Therefore, the current research project focuses on the examination of recently developed MarBN type steels (Martensitic steel strengthened by Boron and Nitrides) and four Grade 92 derivatives in order to evaluate their suitability for 650°C application, and also to assess their creep strength from a microstructural point of view.
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Gustafson, Åsa. "Aspects of microstructural evolution in chromium steels in high temperature applications." Doctoral thesis, KTH, Materials Science and Engineering, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3048.

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In this thesis 9-12 % Cr steels, used for high-temperaturecomponents in fossil-fired power plants are considered. Thecreep strength of thees steels depend on their microstructurethat consists of a matrix of tempered lath martensite withdensely distributed precipitates. The mechanical properties arestrongly influenced by precipitates present in the matrix andthe more densely distributed they are the higher is thehardening effect. These particles nucleate, grow and coarsenduring use in power plants, leading to a degradation ofmechanical properties. In this thesis the nucleation andcoarsening behaviour of the precipitates in the Cr steels aresimulated by new models and the results are compared withtransmission electron microscopy (TEM) observations of testedmaterials.

A model of the nucleation of MX, which mainly isvanadium-nitrides, is presented. MX precipitates are assumed tonucleate on dislocations during annealing. The model takes intoaccount the full multicomponent thermodynamical behaviour ofthe system as well as the strain energy caused by a puredilatoric strain and the shape of the nucleus. The calculationsyield a critical size and shape represented by an oblatespheroid with a radius of a few nanometers and a thickness ofan atomic layer. This is in agreement with TEM observations ofsupercritical particles.

A new coarsening model, which takes into account themulticomponent effects, is presented and it has been tested ondifferent systems to validate the model.

    Four different carbides, Cr7C3, Mo6C, VC and NbC, in austenitic matrix as well asγ ' in ternary Ni-base super-alloy systems (Ni-Al-Mo)were compared with measurements from literature.

    TiC-particles in austenitic stainless steel, ASTM 316Ti,were considered. The simulations were performed taking intoaccount iron and 7 alloying elements. The measurements wereperformed with TEM on samples that had been heat-treated at900° C.

    MX and M23C6in a 9 % Cr steel were investigated with energyfiltering transmission electron microscopy (EFTEM) andcompared with simulations. The used samples had been heattreated for various periods of time at 600 and 650° Cfor up to 26 000 h.

The agreement of the simulations with the experiments wasgood in all cases when reasonable values of the interfacialenergy, the only adjustable parameter, were chosen.

Coarsening simulations were also performed to investigatethe influence of changes in composition on the coarsening rate.For MX, in a 9 % Cr steel, the coarsening rate is almostindependent of the V/Nb ratio but highly dependent on theN-content. Also the effect on the coarsening rate for M23C6by adding Co to a Cr steel was investigated bysimulation. Co is known to increase the resistance totempering. The results show that a final average radius of thecarbides after 30 000 h at 600° C decreases with 30 % witha Co addition of 10 mass %.

Keywords:Cr steels, nucleation, coarsening, model,DICTRA, precipitates, carbides, carbo-nitrides, MX, VN, M23C6, TiC, TEM, EFTEM, Curie-temperature

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Bénéteau, Adeline. "Étude in situ des évolutions microstructurales d'un acier inoxydable martensitique à l'azote au cours d'une succession de traitements thermiques." Thesis, Vandoeuvre-les-Nancy, INPL, 2007. http://www.theses.fr/2007INPL016N/document.

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L’acier inoxydable martensitique à l’azote XD15NW (Fe–15,5%Cr–0,4%C–0,2%N–1,7%Mo–0,3%V) est un candidat attractif pour les bagues de roulement des moteurs spatiaux. Il possède de bonnes propriétés mécaniques et une bonne résistance à la corrosion grâce à l’azote qui contribue à la formation de précipités de petite taille dans une matrice à grains fins. Nous avons étudié les évolutions microstructurales de cet acier au cours d’une succession de traitements thermiques: austénitisation et trempe, revenu, traitement de surface par induction. Outre les techniques usuelles d’analyse microstructurale (MEB, MET, dilatométrie), nous avons utilisé la diffraction des rayons X de haute énergie in situ (rayonnement synchrotron). Cette technique nous a permis d’obtenir les cinétiques d’évolution des phases en fonction de la température et du temps, les gradients de microstructure au sein de pièces traitées par induction en surface et les évolutions de paramètres de maille des phases
The nitrogen martensitic stainless steel XD15NW (Fe–15,5%Cr–0,4%C–0,2%N–1,7%Mo–0,3%V) is an attractive candidate for the bearing rings of the space engines turbopumps. It owns good mechanical properties and a good corrosion resistance thanks to the nitrogen which contributes to the formation of little size precipitates in a fine grains matrix. The microstructural evolutions of this steel during a succession of thermal treatments were studied: austenitisation and quenching, tempering, induction surface heat treatment. In addition to the usual techniques of microstructural analysis (SEM, TEM, dilatometry), the in situ high energy synchrotron X-ray diffraction was used. It allowed to obtain the evolution kinetics of the phases as a function of temperature and time, the microstructural gradients in induction treated samples and the lattice parameters evolutions which are linked to the chemical composition or the internal stresses evolutions of the phases
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Maetz, Jean-Yves. "Évolution de la microstructure d’un acier inoxydable lean duplex lors du vieillissement." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0008/document.

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Les aciers inoxydables lean duplex sont une famille d'aciers austéno-ferritiques allégés en nickel et en molybdène, qui s'est développée à la fin des années 1990. Le compromis propriétés mécaniques, propriétés de résistance à la corrosion et coût de matière première place cette famille comme une alternative intéressante aux aciers austénitiques standards, et en particulier aux 304/304L qui représentent actuellement les deux tiers de la production d'acier inoxydable. Cependant, cette famille étant relativement récente, la stabilité en température des aciers lean duplex a été relativement peu étudiée, en particulier lors de maintiens prolongés en température. Dans le cadre de cette thèse, l'évolution microstructurale d'un acier lean duplex 2101 a été étudiée, lors de vieillissements isothermes à des températures comprises entre 20 °C et 850 °C, pour des temps s'échelonnant de quelques minutes à plusieurs mois. Les cinétiques de vieillissement ont été suivies par mesures de pouvoir thermoéléctrique (PTE), à partir desquelles des états vieillis ont été sélectionnés pour être caractérisés par microscopie électronique et par sonde atomique tomographique. A des températures intermédiaires de 350 – 450 °C, la ferrite de l'acier lean duplex 2101 est sujette à la démixtion Fe-Cr et à la formation d'amas enrichis en Ni-Mn-Si-Al-Cu, malgré les faibles teneurs en nickel de cette nuance. Ces phénomènes sont détectés par une forte augmentation du PTE. Pour des températures plus élevées, à 700 °C environ, une approche multi-techniques et multi-échelles a permis de décrire précisément les mécanismes qui régissent les différentes évolutions microstructurales : la germination et la croissance de M23C6 et de Cr2N, observés dès quelques minutes de vieillissement aux joints de phases, la précipitation de la phase σ pour des temps de vieillissement plus importants qui s'accompagne d'une transformation de la ferrite δ en austénite secondaire γ2, et la transformation partielle de l'austénite en martensite lors du refroidissement des échantillons vieillis. L'effet des différentes phases sur le PTE de l'acier lean duplex peut être décrit qualitativement lors du vieillissement par une loi des mélanges
Lean duplex stainless steels are austeno-ferritic steels with lower nickel and molybdenum contents, developed in the late 90's. Considering mechanical properties, corrosion resistance and cost of raw material, this family is an interesting alternative to standard austenitic stainless steels, which currently represent two thirds of stainless steel production. However, lean duplex steels are relatively recent and their thermal stability has been relatively little studied, especially during long term aging. In this study, the microstructural evolution of a lean duplex steel 2101 was studied during isothermal aging at temperatures between 20 °C and 850 °C, from few minutes to several months. Aging kinetics were followed by thermoelectric power measurements (TEP), from which aged states were selected to be characterized by electron microscopy and atom probe tomography. At intermediate temperatures of 350 - 450 °C, Fe-Cr demixing and precipitation of Ni-Mn-Al-Si-Cu occur in the ferrite despite the low nickel content of this grade, leading to an increase in the TEP. For higher temperatures, at about 700 °C, the mechanisms which govern the different microstructural evolutions have been described by a multi-scale approach: the nucleation and growth of M23C6 and Cr2N, observed from few minutes of aging and the σ phase precipitation, observed for longer aging time. The latter is accompanied by a transformation of δ ferrite in γ2 secondary austenite, and by the partial transformation of austenite into martensite during cooling. The effect of different phases on the TEP of the lean duplex steel can be qualitatively described during aging by a rule of mixture
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Krishna, Ram. "Microstructural investigation of alloys used for power generation industries." Thesis, University of Leicester, 2010. http://hdl.handle.net/2381/8601.

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Nickel based superalloys are currently being investigated for high temperature applications in advanced steam power plant operating at temperatures of 700˚C and above. Three nickel-based superalloys Inconel 617, Inconel 625 and Nimonic 263 alloys, which are of primary interest for boiler technology components such as furnace walls, superheater tubes, header and steam pipes, etc and for steam turbine technology components such as HP &IP cylinders, rotor forgings, casing and valve chest, blading, etc., have been evaluated for long and short term creep performance. Creep deformation processes occurring at high temperatures and stresses lead to the evolution of microstructures in the form of precipitation, precipitate coarsening and recovery effects. The deterioration in mechanical properties as a result of this microstructural change has been evaluated by hardness testing. This work discusses the microstructural evolution occurring in alloys in samples that have been creep exposed at a series of temperatures from 650°C to 775°C and for durations from 1000 to 45,000 hours using advanced FEGSEM, TEM, XRD and phase extraction techniques. The fractions and morphology of different phases, their locations during exposure to higher temperatures and probable creep fracture mechanism in these alloys are illustrated and discussed.
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Sjöström, Julia, and Helena Åkesson. "Investigation of Ductility Dip at 1000˚C in Alloy 617." Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209823.

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Alloy 617 displays a ductility dip during straining at exactly 1000˚C, leading to brittle fracture. A sudden decrease in ductility appearing during Gleeble hot ductility tests of Ni-based superalloys is a well-known phenomenon, while its cause is unknown. Many mechanisms have been established as possible contributors to the issue, and in later years not one, but the simultaneous presence of several of these mechanisms were confirmed as the cause. The ductility dip leads to solid state cracking and a specific solid state cracking phenomenon known as ductility dip cracking is specifically common in Ni-based superalloys. Ductility dip cracking is identified by intergranular cracks and the occurrence of specific precipitates, among other things. This work investigates the possibility that the decreased ductility is due to ductility dip cracking. Furthermore, other possible explanations are investigated. Visual examination was conducted through LOM, SEM and chemical analysis using EDS technique. Combined with thermodynamic calculations, the existence of Cr-rich M23C6 carbides, Ti(N,C) and Mo-rich particles, most likely M3B2, were confirmed. Further, it is established that the ductility dip is related to the lack of dynamic recrystallization at 1000˚C. It is not confirmed that the ductility dip in alloy 617 is due to ductility dip cracking.
Nickelbaslegeringen 617 uppvisar en minskning i duktilitet under Gleeble-dragprovning vid exakt 1000˚C vilket leder till sprött brott. En plötslig sänkning av duktiliteten vid varmdragning av Ni-baserade superlegeringar är ett välkänt fenomen, dock är orsaken inte fastställd. Många mekanismer har bekräftats som bidrag till problemet och under de senaste åren har den simultana närvaron av fler av dessa mekanismer bekräftats som orsaken. Sänkningen i duktilitet leder till sprickbildning i fast fas och en specifik typ av sprickbildning känd som ”ductility dip cracking” är speciellt förekommande i Ni-bas legeringar. Denna identifieras bland annat genom intergranulära sprickor och närvaron av specifika utskiljningar. Detta arbete undersöker möjligheten att duktilitetssänkningen beror på  ”ductility dip cracking”. Dessutom undersöks fler tänkbara förklaringar. Visuell granskning genomfördes via LOM och SEM och analys av sammansättningar via EDS-analys. I kombination med termodynamiska simuleringar blev förekomsten av Cr-rika M23C6 karbider, Ti(N,C) och Mo-rika partiklar, troligtvis M3B2, bekräftad. Fortsatt är det bekräftat att duktilitetssänkningen är relaterat till avsaknaden av rekristallisation vid 1000˚C. Det är inte bekräftat i detta arbete att duktilitetssänkningen i legering 617 beror av ”ductility dip cracking”.
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Calcinelli, Luca. "Ottimizzazione del trattamento termico di acciai inossidabili martensitici per stampi." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.

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L’acciaio inossidabile martensitico AISI 420 viene impiegato per la realizzazione di stampi per la formatura di materie plastiche grazie alle sue elevate proprietà di resistenza all'usura e stabilità dimensionale. Esse sono funzione del trattamento termico che esso subisce e che può compromettere proprietà meccaniche e corrosive tipiche di questo acciaio. Il presente studio prende avvio proprio da queste considerazioni e dagli esiti di alcune failure analysis su stampi per bottiglie in PET, in cui sono state evidenziate rotture per fatica innescate da pitting corrosivo con propagazione intergranulare. Nell’ambito della sperimentazione riportata si è cercato di ottimizzare il trattamento termico di bonifica in modo da massimizzare resistenza a corrosione, a fatica e resilienza pur garantendo una sufficiente stabilità dimensionale. A seguito di un approfondimento bibliografico, si è definita una microstruttura obiettivo caratterizzata dalla presenza di carburi M23C6 globulizzati ed uniformemente distribuiti nella matrice martensitica e si sono testate differenti condizioni di trattamento termico. L'esito della sperimentazione, che si è avvalsa di tecniche di microscopia ottica ed elettronica, ha indicato come trattamento ottimale quello costituito da una austenitizzazione di 30 minuti a 1020°C seguito da una tempra in azoto a 10 bar ed un ciclo di tre rinvenimenti a 250°C. La ridotta temperatura di austenitizzazione ha permesso la limitazione dei tenori di austenite residua mentre elevata velocità di raffreddamento impiegata e ridotte temperature di rinvenimento hanno permesso di evitare la precipitazione di carburi fini infragilenti e causa di sensibilizzazione. Sono state inoltre eseguite numerose analisi che hanno permesso di accertare una certa variabilità microstrutturale del materiale allo stato di fornitura evidenziando come la microstruttura di quest'ultimo sia fondamentale per ottenere l'esito desiderato dal trattamento termico.
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Book chapters on the topic "M23C6"

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Zhigang, Song, Feng han, Zheng Wenjie, Zhang Lihong, Ma Mingjuan, and Sang Weijun. "Research on M23C6 precipitation of 690 alloy." In Energy Materials 2014, 459–65. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-48765-6_54.

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Vodárek, V., and A. Strang. "The Effect of Nickel on M23C6 Coarsening Rates in 12CrMoVNb Steels." In Solid State Transformation and Heat Treatment, 12–18. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2005. http://dx.doi.org/10.1002/3527604839.ch2.

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Gao, Shuang, Jieshan Hou, Fei Yang, Changshuai Wang, and Lanzhang Zhou. "Precipitation Behaviors of M23C6 Carbides and γʹ Phase in Cast IN617B Alloy During Long-Term Aging." In High Performance Structural Materials, 685–92. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-0104-9_72.

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Chen, Jun, Zhenjie Zhang, Xiaofei Ding, Haitao Ma, and Haoran Ma. "Microstructure Evolution and Element Redistribution in Carburizing Process of Ethylene Cracking Furnace Tube." In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220415.

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Carburizing is the main damage form of ethylene cracking furnace tubes. In this process, the microstructure of the furnace tube would change and the element diffuses and redistributes. After serving for about 41000h, the radiation section of a plum blossom tube of SC-1 tubular cracking furnace from a petrochemical company was tested and analyzed in this article. Results show that the higher the service temperature, the more serious the carburizing of the furnace tube. In the inner-wall carburized zone of the middle temperature section of the furnace tube with an initial C content of 0.1wt%, the maximum C content reaches 1.83wt% and the number of carbides increases obviously as well as its organizational morphology changes from fine granular to coarse block or chain like and its organizational type changes from single M23C6 to the coexistence of M23C6, M7C3 and MC type carbides. The Cr and C elements in the carburized zone are mainly concentrated in the grain boundary area in the form of carbides. At the same time, the diffusion of alloy elements causes Cr deficiency in the matrix, and the carbide deficiency zone appears in the subsurface of the inner wall.
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Miao, Baihe, and Xishan Xie. "Interfacial Structure of M23C6/γ and VC/γ in a Carbide Strengthening Superalloy." In Strength of Metals and Alloys (ICSMA 8), 1339–44. Elsevier, 1989. http://dx.doi.org/10.1016/b978-0-08-034804-9.50212-6.

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Conference papers on the topic "M23C6"

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Baolan, Gu, and Xu Tong. "Impact Toughness of Grade 92 Steel Aging at 700°C." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65479.

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The evolution of microstructures and the variation of impact toughness of Grade 92 steel aged 200,500, 800, 1000 hours at 700 °C were studied in this paper. The results show that the impact energy of Grade 92 steel was reduced significantly with the aging time increase. After 200 h aging, the value of impact energy decreased about 10%; then the impact energy variation trends to be stable with 500 h aging. When the aging time increase to 800 h, the impacts energy decreased about 26% compared with the original sample; and then the variation trends stable with 1000 h aging. The precipitation and growth of M23C6 Phases at the prior austenite grain boundaries and martensitie lath boundaries during aging are major reasons of the impact energy decrease. 200 h aging, M23C6 carbides precipitate at the grain boundaries. Laves phase was discovered after 500 h aging, then the M23C6 and Laves phase coarsening with the aging time. This made the impact toughness degradation more.
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Zhong, Qiang, Man Wang, Wen-Qiang Sun, Jun-Jie Wu, Jiong Qian, and Sen-Sen Ning. "Effect of Carbon Content on the Resistance to Intergranular Corrosion of Alloy 800H." In 2022 29th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icone29-91676.

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Abstract The effect of carbon content on the intergranular corrosion performance of Alloy 800H was studied by thermodynamic software simulation calculation combined with double-loop electrochemical potentiodynamic reactivation (DL-EPR), sulfuric acid-copper sulfate test, and microscopic morphology observation (optical microscope, scanning electron microscope). The results show that the main precipitation phases of Alloy 800H are α-Cr phase, M(C,N), M23C6, η phase and σ phase. At 500∼720°C, the higher the carbon content and the more M23C6 phase, the higher the susceptibility to intergranular corrosion. In the solid solution state, the Alloy 800H has low sensitivity to intergranular corrosion, and the carbon content has no obvious effect on its resistance to intergranular corrosion. In the sensitized state, carbides are continuously precipitated at the grain boundaries, and the intergranular corrosion susceptibility of the alloy increases rapidly.
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Ivanov, Yurii, Anatolii Klopotov, Elizaveta Petrikova, Yurii Vlasov, and Alexey Kondratyuk. "Phase transformations during high-speed heat treatment of the system “carbide (M23C6)/(α-Fe) matrix”." In PROSPECTS OF FUNDAMENTAL SCIENCES DEVELOPMENT (PFSD-2017): Proceedings of the XIV International Conference of Students and Young Scientists. Author(s), 2017. http://dx.doi.org/10.1063/1.5009852.

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Yu, Chi, Feng Yang, and Jinping Suo. "The Effect of Ti, N and V Content and Heat Treatment on Irradiation and Mechanical Property of SCRAM Steels." In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-30625.

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An Fe-Cr-W-V-Ti-N steel named SCRAM (super-clean reduced-activation martensitic) steel was designed for the first wall and blanket structure of fusion power plants. Compared with the Fe-Cr-W-V-Ta steel, TiN can precipitate first at 1650°C rather than TaC by the Thermal-cal Calculation. And we take vacuum induction melting (VIM) and electro-slag re-melting (ESR) together to manufacture the SCRAM steel, which can make the TiN fine and the steel pure. Mechanical properties and microstructures of SCRAM steels irradiated with single-beam (Fe) and sequential-beam (Fe plus He and Fe plus H) at 300°C were studied. The results show that, SCRAM steel can have better mechanical properties before and after irradiation while Ti was doped into the SCRAM steel. It has been reported that the precipitation formed in the steel has effect on the mechanical properties, irradiation properties and the ductile brittle transition temperature (DBTT). The effect of intermediate heat treatment on precipitation behavior and mechanical properties of SCRAM steel was investigated in order to obtain dispersed fine M23C6 carbides. The results indicated that MX carbonitrides precipitated first in the steel with intermediate heat treatment at 870°C rather than M23C6, which led to a decrease of carbon concentration in the supersaturated martensitic matrix and correspondingly a reduced volume fraction and mean size of M23C6. The intermediate heat treatment was beneficial to the mechanical properties, and proposed for reduction on the ductile brittle transition temperature (DBTT).
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Che, Chang, Xiang Liu, Youqiao Huang, Qingchuan Pan, and Gong Qian. "Characterisation of the Microstructure Evolution of Aged Grade 91 Steel." In ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21201.

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Abstract Grade 91 steel has high creep strength and has been used as the material of piping in 600°C USC power plants in China. The Grade 91 materials used in actual power plants are useful in estimating the changes of material properties caused by long-term aging and damage at low stress conditions. An understanding of the long-term microstructural evolution under actually used conditions is a key for the improvement of these heat resistant steels. In this article, microstructural evolution of Grade 91 steel under different service conditions in Chinese power plants was studied using optical microscope (OM), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) techniques. The results show, M23C6, MX (V-rich particles; Nb-rich particles), and Laves phases were found to precipitate. A quantitative characterisation of microstructure evolution was evaluated during long-term exposure, focusing on the size of precipitates (M23C6 carbides, Laves phase, MX phase) for the Grade 91 steel after long-term service.
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Yang, Chengdong, Maolong Zhang, Xiangkun Ru, and Weibao Tang. "The Effect of Nozzle Safe End Hot/Cold Wire Tungsten Inert Gas Buttering on Microstructure and Property." In 2022 29th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icone29-89075.

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Abstract Hot wire tungsten inert gas (HWTIG) and cold wire tungsten inert gas (CWTIG) have been used for nozzle safe-end buttering of nuclear island critical equipment, the effect of the HWTIG and CWTIG buttering on microstructure and property has been investigated. Research results revealed that the grain orientation of HWTIG buttering layer is mostly concentrated in (0 0 1) direction and the average grain size is 118.375μm, while the grain orientation of the CWTIG dispersed distribution in (0 0 1), (1 1 1) and (1 0 1) direction, and the grain size is 158.479μm. Furthermore, the grain boundary misorientation angle of HWTIG buttering layer has higher occurrence frequency between 10° and 30° high-angle boundary, whereas the CWTIG has higher occurrence frequency within 30° and 60°. Moreover, the microstructure of HWTIG buttering layer has less chromium-rich M23C6-type carbide compared to CWTIG, and the M23C6-type carbides discontinuous distribution on the grain boundary of HWTIG buttering layer. The buttering layer of HWTIG has lower ductility-dip cracking sensitivity than CWTIG.
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Wang, Yiyu, Rangasayee Kannan, Leijun Li, Yasin Suzuk, Darren Ting, Simon Yuen, and Maria Marilin Garcia. "Jagged Cracking in the Heat-Affected Zone of Weld Overlay on Coke Drum Cladding." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-66118.

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Jagged cracks were observed in SA240 Type 405 stainless steel cladding of Inconel 625 overlay repaired coke drums. It is found that intergranular cracking is the dominant fracture mode in the fine-grained heat-affected zone (FGHAZ) of the boat specimens. The sensitization effect from the operation and welding thermal cycles leads to the depletion of Cr with the preferential precipitation of Cr-rich M23C6 carbides along the grain boundaries. The cladding FGHAZ has the largest frequency of grain boundaries with higher local strain levels and the highest fraction of grain boundary Cr-rich M23C6 carbides. Thermal stress distributions predicted by finite element analysis clearly show the maximum shear stress to exhibit the typical “jagged” pattern near the cracked regions. Thermal expansion coefficient and strength mismatch among the shell base metal, cladding, and overlay is believed to have caused the unique jagged maximum shear stress distribution in the cladding HAZ of Inconel 625 overlay. The magnitude of this thermal stress can reach the yield strength of the cladding at 900 °F (482 °C) service temperature, therefore, provides the driving force for the jagged cracking formation in the sensitized HAZ.
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Laigo, Johanne, Franck Tancret, Rene´ Le Gall, Fre´de´ric Christien, and Jader Furtado. "The Influence of Phase Transformations on Creep Resistance in Fe-Ni-Cr Alloys for Reformer Tube Applications." In ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/creep2007-26720.

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Heat resistant steels of the HP-series have widespread uses in the petrochemical industry in pyrolysis and reformer furnaces. The alloys are carbon-rich Fe-Ni-Cr alloys, with additions like Mn, Si, Nb, Ti, W... The typical microstructure of as-cast HP alloys is an austenite matrix with intergranular eutectic-like primary chromium carbides of the M7C3 type and niobium carbides of the MC type. Upon ageing, phase transformations occur. Intragranular secondary M23C6 carbides precipitate, which is thought to restrict dislocation motion, and intergranular M7C3 transforms into M23C6. Under certain thermal conditions, a partial transformation of the primary niobium carbides into a nickel-niobium silicide called G phase can occur. These phases may play a critical role during creep, but neither their role on mechanical properties nor the mechanisms of phase transformations are clearly identified. The aim of this study is to understand the role of each phase or phase transformation in the creep resistance of HP alloys. Consequently, a critical review of phase formation and transformations in such alloys is presented using a set of experimental and modelling techniques (electron microscopy, Castaing microprobe, creep tests at high temperature and neural networks modelling of mechanical properties...).
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Yamamoto, Yukinori, Xinghua Yu, and Sudarsanam Suresh Babu. "Improvement of Creep Performance of Creep Strength Enhanced Ferritic (CSEF) Steel Weldments Through Non-Standard Heat Treatments." In ASME 2014 Symposium on Elevated Temperature Application of Materials for Fossil, Nuclear, and Petrochemical Industries. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/etam2014-1009.

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Significant improvement of creep-rupture life was observed in Grade 91 (modified 9Cr-1Mo) steel weldments when a non-standard heat-treatment was applied prior to welding. A lower temperature pre-weld tempering (LTT) than the typical heat-treatment resulted in a complete dissolution of M23C6 carbides in the fine-grained heat affected zone (FGHAZ) during welding, which allowed re-precipitation of the M23C6 as strengthening carbides after post-weld heat treatment. However, the LTT also raised the ductile-brittle transition temperature of the base metal above room temperature. A thermo-mechanical treatment (TMT) has been proposed in the present study as a way of balancing the need for improved creep properties in the weld region and an acceptable level of room temperature ductility in the base metal. Aus-forging and subsequent aus-aging promotes MX formation prior to martensitic transformation which effectively increases the creep resistance, even in the FGHAZ. The application of the standard tempering after the TMT process improves the room temperature ductility without losing the advantage of improved strength. Preliminary results indicate a successful improvement of the cross-weld creep properties of the TMT sample similar to the LTT sample. Paper published with permission.
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10

Hamaguchi, Tomoaki, Hirokazu Okada, Shinnosuke Kurihara, Hiroyuki Hirata, Mitsuru Yoshizawa, and Atsuro Iseda. "Microstructural Evaluation of 9Cr-3W-3Co-Nd-B Heat-Resistant Steel (SAVE12AD) After Long-Term Creep Deformation." In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65241.

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The new ferritic heat-resistant steel composed of 9Cr-3W-3Co-Nd-B, registered as ASME Code Case 2839, has been developed for large diameter and heavy wall thickness pipes and forgings of fossil-fired power boilers. The steel, which contains 0.01 mass% boron, a small amount of neodymium, and optimized amounts of nitrogen, is characterized by the superior long-term creep strengths of both the base metal and welded joint. P92 had equiaxed subgrain structures changed from martensite lath structures and coarsened M23C6 type carbides after long-term creep. In contrast, the developed steel, SAVE12AD, maintained martensite lath structures with fine M23C6 along the boundaries even after the long-term creep stage. The addition of high amounts of boron suppressed the coarsening of M23C6 along the boundaries, thereby stabilizing the martensite lath structure in the base metal of the steel. Consequently, SAVE12AD had higher creep rupture strength than other high chromium ferritic steels. To investigate the creep rupture strength of welded joints, two welded joints with Ni-based alloy and Grade 92 welding filler wires were prepared by automatic gas tungsten arc welding. The creep rupture strength of each welded joint showed small degradation compared with the base metal in the long-term creep stage over 10,000 hours. These were ruptured 1.5 mm away from the fusion line, which was the same area as Type IV cracking. Microstructural observations were carried out by electron back scatter diffraction analysis using simulated heat-affected zone samples at different peak temperatures from 750 °C to 1350 °C in order to clarify the microstructure in the heat-affected zone. No fine grain area was observed in the microstructure after the simulated heat-affected zone at 910 °C just above AC3 transformation temperature, although there were fine grains along prior austenite grain boundaries, which seemed to form with the diffusion transformation. The creep cracks seemed to have initiated from the fine grain structures, resulting in the rupture at the same area as Type IV cracking. However, the creep rupture strength degradation of the welded joints against the base metal was significantly smaller than that of conventional steel welded joints owing to the suppression of fine grains found in the heat-affected zone heated around AC3 temperature. The developed 9Cr-3W-3Co-Nd-B steel (SAVE12AD) will be used for large diameter and heavy wall thickness pipes and forgings in 600 °C ultra super critical power plants.
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