Dissertations / Theses on the topic 'Stainless steel components'

Nuclear plant stainless steel can become contaminated by radionuclides during normal operation whereby the final disposition of these materials then becomes a major decommissioning challenge to address. Characterisation of the chemical and metallurgical processes that underpin contamination is essential in consideration of developing cost effective decontamination and prevention methods, as are in situ measurement techniques that allow assessment of contamination. To address these issues, contamination experiments to simulate the nitric acid-based reprocessing streams of the PUREX (Plutonium Uranium Redox Extraction) process, and alkaline spent fuel storage ponds were investigated. Solution and surface spectroscopic measurements were performed to characterise the sorption behaviour of stable analogues of two high yield fission products, Sr-90 and Cs-137, on as received and 30 % cold rolled AISI Type 304 stainless steel, respectively. In addition Laser Induced Breakdown Spectroscopy (LIBS) was also investigated as a standoff contamination assessment technique. Fission product accumulation was modelled to a second order kinetic fit that considers chemisorption, typically to a hydrous metal oxide surface, as rate controlling. This process is observed to be independent of solution composition and strain processing regime. This behaviour reflects complexation to the passivating surface chromium oxide film, and as determined by depth elemental analysis, effectively inhibits contaminant migration into the bulk material. Environment chemistry and microstructural variables that destabilise the Cr-rich passive film however reduces the passive layer capabilities to effectively inhibit fission product bulk diffusion. The importance of corrosion phenomena towards radionuclide sorption processes necessitates the consideration of metallurgical and chemical factors during the implementation of decontamination approaches to treat affected plant material at nuclear licenced sites. LIBS was found to be a satisfactory technique for measurement of Sr sorbed to steel but Cs could not be detected at the concentrations used in this experimentation. Furthermore, EDX and TOF-SIMS elemental mapping indicated ablated material may be redistributed into the crater profile during elemental analysis. This process has clear implications for the deployment of LIBS for in situ characterisation of nuclear materials as the uncontrolled redistribution of radioactive material certainly violates decommissioning principles.

The purpose of this research was the investigation of the corrosion behavior of a low chromium-content stainless steel, ASTM A1010, for use in steel bridge members. This stainless steel has been marketed as a potential replacement for conventional structural steels for bridges located in highly-corrosive environments, with the potential to provide life-cycle cost savings. Further investigation of the corrosion behavior of A1010 in corrosive environments was required for three bridge-specific applications: the galvanic corrosion of A1010 connected to plates and fasteners composed of dissimilar metals; the crevice corrosion of A1010 plates connected with other A1010 plates; and the effect of varying surface preparation techniques on the corrosion behavior of A1010. These behaviors were studied through the implementation of an accelerated cyclic corrosion test, the modified SAE J2334 Surface Vehicle Standard specification. Results from the accelerated corrosion test indicated the following: galvanic corrosion rates of A1010 with dissimilar metal plates may result in accelerated corrosion rates of the dissimilar metal plates beyond desirable levels; connections to many non-stainless fastener types show cause for concerns with galvanic corrosion, while B8 Class 2 austenitic stainless steel bolt assemblies exhibited superior performance; the relative corrosion-resistance of A1010 is decreased in detailing susceptible to crevice corrosion; and finally, numerous abrasive blasting procedures appear to be suitable for use with A1010.<br>Master of Science

This thesis describes the work carried out in an investigation of crack growth behaviour in 316L steel hollow cylindrical components subjected to conditions of thermal fatigue interacting with creep. Type 316L austenitic stainless steel is a widely used material for high-temperature structural components such as heat exchangers. A thorough knowledge of its behaviour in the presence of severe cyclic loading with dwell times at high temperature and under the superimposition of sustained mechanical loads is highly desirable. A review of the relevant literature background, necessary to understand both the fatigue and creep mechanisms in relation to crack initiation and growth, is given. Physical and mechanical properties of the material under examination are then presented. The design and construction of a unique experimental facility able to reproduce the required conditions of creep/thermal fatigue interaction is described. In order to generate the required temperature gradients, induction heating was used to cyclically heat the external surface of thick-walled cylindrical component between 80° and 600°C while the internal surface was cooked by water flow. A mechanical load could be axially introduced in the specimen by means of a dead-weight creep machine. Artificial defects, simulating actual stress concentrators in real components, acted as crack starters. The direct current potential drop method was used for in-situ real-time crack growth monitoring. A significant experimental activity was completed under a combination of varying experimental parameters, such as hold time, severity of the thermal shock and primary load. Numerical methodologies were applied to predict stress fields during cycling and to assess cracking rates. Fracture mechanics crack tip parameters were evaluated. An "effective" stress intensity factor range proved to yield satisfactory results in correlating the experimental data. A general discussion in which the experimental results are analysed is given. Finally, the principal findings are summarised and some areas for future investigation proposed.

This master thesis was carried out at Scania CV AB. The focus for this thesis is the prediction of welding distortions that can cause problems in the manufacturing process of Scania's after-treatment system. The after-treatment system is mainly assembled by sheet metal plates of the ferritic stainless steel EN 1.4509. The plates are welded together. When welding, distortions and residual stresses occur, and they also depend on the sequence in the component was welded together. The distortions and residual stresses can cause tolerance related issues and a lower lifetime for the welded components. Experiments are expensive and therefore it is desirable to simulate the welding process, thereby controlling distortions and optimizing welding sequences. To simulate the welding process and predict the welding distortions a thermo-mechanical FE-model was created for two typical welds found on the after-treatment system. The first scenario was two thin plates welded onto each other in an overlap weld joint and the second scenario was a thin plate welded onto a thick plate in a overlap weld joint. After the FE-model was compared to the experiments. An optimization of the welding sequences was also made on a larger component typically found on the after-treatment system. The FE-model can predict the distortion shape with good accuracy for the T-fillet weld, while the model predicted a more symmetric distortion shape on the overlap weld compared to a more asymmetric shape found on the experiments, but the error is still not very large. The Fe-model can also be used to optimize the welding sequence for bigger components on the after-treatment system within a reasonable time span compared to doing the opimization manually in an experiment.<br>Detta examensarbete gjordes för Scania CV AB. Fokus for detta examensarbete har varit kvarvarande deformationer efter svetsning som kan skapa problem vid tillverkningen av Scanias avgasefterbehandlingssystem. Avgasefterbehandlingssystemet är till mesta dels konstruerat av stålplåtar av det ferritiska rostfria stålet EN 1.4509, plåtarna är svetsade ihop och då uppstår kvarvarande deformationer. När komponenter svetsas samman uppstår deformationer och restspänningar. Dessa deformationer och restspänningar är också beroende på i vilken sekvens komponenterna har svetsats ihop. Deformationerna och restspänningarna kan skapa problem med toleranser och sänka livslängden för komponenterna som sammanfogats. Experiment är kostsamma och därför är det önskvärt att simulera svetsprocessen, och därav kontrollera deformationerna som uppstår och optimera i vilken sekvens som komponenterna ska svetsas ihop. För att simulera svetsprocessen och prediktera de kvarvarande deformationerna efter svetsning så gjordes termo-mekanisk FE-model för två vanliga svetsscenarion för avgasefterbehandlingssystemet. Det ena scenariot är två tunna plåtar som svetsas ihop i en överlappande position och det andra var en tunn plåt som svetsas på en tjockare plåt. Ett experiment gjordes sedan för båda svetstyperna. Efter att svetstyperna hade jämförts med experimentet så gjordes en optimering av svetssekvensen för en större komponent likt komponenter funna på avgasefterbehandlingssystemet. Den termomekaniska FE-modelen kunde prediktera de kvarnvarande deformationerna och deras form med bra noggrannhet jämfört med experimentet med undantag för en deformationsform på de tunna plåtarna som var mer symmetrisk i FE-modellen jämfört med den asymmetriska formen i experimentet. FE-modellen kunde också användas för att optimera svetssekvensen för den större komponenten inom en rimlig tidsrymd.

The contamination of 316L stainless steel surfaces within an electrospray ionisation source of a mass spectrometer is investigated. An accelerated method of contamination is used. Following initial test method development and investigation of the contamination resulting on the ion transfer components (sample cone, outer cone and extraction cone), flat samples are employed within the ionisation source. This enables characterisation of the contamination composition, morphology and build-up with time. Blood plasma is introduced into the mass spectrometer as it is a widely analysed substance that is known to result in contamination. The contamination from a mixture of human blood plasma, diluted in methanol, and a water/acetonitrile mobile phase is found to contain inorganic NaCl crystals embedded in a matrix of organic residues. The morphology shows self-organising features as the contamination builds. A model is proposed to explain the morphology, involving rapid evaporation of the droplets that impinge on the stainless steel surface. Two types of surface modification are considered for the stainless steel: electrochemically grown films and coatings deposited by vapour deposition. A method for electrochemical film growth is developed, enabling nanoporous films to be formed on the stainless steel in 5 M sulphuric acid at 60°C by square wave pulse polarisation between active or transpassive and passive potentials. The films are characterised using glow discharge optical emission spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, Rutherford backscattering spectroscopy and nuclear reaction analysis. The films are shown to be chromium- and molybdenum-rich relative to the substrate, and to consist mainly of sulphates, oxides and hydroxides. The morphology and composition of the films are discussed in relation to the polarisation conditions and mechanism of film formation. A range of vapour deposited coatings are considered: TiN, TiC, TiB2, Graphit-iC, and diamond-like carbon coatings with Si and N2 dopants and with varying sp2:sp3 ratios. In addition, a hydrophobic coating is deposited on the stainless steel by immersion, in order to provide a significant variation in surface energy. Surface analysis of the coatings is carried out, considering their sp2:sp3 ratios, their electrical conductivities, their water contact angle, and the various components of the surface energy. The contamination build-up on the surface of uncoated 316L stainless steel is compared with that on stainless steel with the various surface modifications. A method for quantification of the build-up of contamination on flat samples is developed using white light interferometry. The surface modifications which result in the slowest contamination build-up with time are then applied to the ion transfer components of the mass spectrometer. The robustness of the mass spectrometric response for the selected coated surfaces is compared with that of the uncoated stainless steel. The electrochemically grown films and two of the doped diamond-like carbon coatings are found to be successful in reducing the build-up of contamination.

This thesis presents a new approach to fabricate high precision micro machine components from stainless steel and stainless steel ceramic composite materials, using Softlithography and powder metallurgy processes. Three different 316-L stainless steel powders, including 5, 10 and 16 μm in size, and two different ceramics powders, including 400 nm alumina and 320 nm titania, were tested. The PhD research process can be divided into three main stages. In the first stage, high quality SU-8 master moulds and their negative replicas soft moulds are produced using Softlithography technique. The second stage includes preparing the stainless steel slurries, filling the soft micro moulds, obtaining the green micro components, de-binding and sintering. In the third stage, the fabrication process has been developed further to produce stainless steel-ceramic composite micro components. Fabrication process in each stage was investigated in detail and the optimum properties were produced. Dispersant acrylic-based binder is adopted in this research successfully in producing damage-free green micro components. A cold isostatic pressing technique is also adopted to improve the densities and linear shrinkages of the stainless steel green and sintered micro components. A new mixing method is used to improve the homogeneity of the ceramic inclusions in the stainless steel matrix of the composite micro components. Characterization of the sintered stainless steel and composite micro components in terms of shape retention, density, linear shrinkage, internal structure, hardness and surface roughness were investigated in detail. The resultant stainless steel and composite micro components retain the same high geometric quality as the SU-8 master moulds.

Structural integrity assessment of nuclear components assessed using the R6 Failure Assessment Diagram approach requires an understanding of the limiting condition in terms of both fracture and plastic collapse. For ductile materials, such as stainless steels used for nuclear components, including the primary pipe-work of a Pressurised Water Reactor (PWR), the limiting condition defined by plastic collapse is likely to occur prior to the initiation of fracture. This is due to the relatively low yield stress of the material and the high fracture toughness. If this is the case, structural integrity may be solely assessed on plastic collapse criteria, with little or no reference to fracture toughness; thus considerably simplifying the assessment procedure, whilst maintaining the integrity of the plant. Nevertheless, an in-depth understanding of fracture under plastic collapse conditions is required to make a robust case for single parameter assessments based on a plastic collapse criterion alone. The challenge in this project lay in understanding and predicting ductile fracture initiation under large-scale yielding conditions, i.e. outside the normal validity limits of conventional elastic-plastic fracture mechanics as plastic collapse conditions are achieved. The approach developed in this research has explored three fracture assessment methods: (a) two parameter fracture mechanics based on the J-integral and a refined Q-parameter calculated closer to the crack-tip under widespread plasticity than is conventionally the case, (b) two local approach methods based on critical void growth ratio defined by Rice and Tracey, and (c) a local approach method based on the critical work of fracture. All three methodologies were found to adequately describe failure across a range of constraint conditions. The fracture toughness constraint dependence of 304(L) stainless steel was studied experimentally and analytically. Significant constraint loss was shown to occur in nominally high constraint fracture toughness specimens due to extensive plastic deformation at fracture initiation. Furthermore, significant fracture toughness constraint dependence was observed experimentally. An analytical method using local approach criteria was developed to predict high constraint fracture toughness, required for structural integrity assessments, and to quantify the constraint dependence fracture toughness as a function of two parameter fracture mechanics based on the J-integral and the refined Q-parameter. The influence of constraint on the prediction of failure in a stainless steel pipe containing a fully circumferential crack of various depths was investigated analytically for a range of loading conditions. A refined constraint independent failure assessment methodology was developed using local approach analyses. Using this methodology, the pipe component was shown to consistently fail by plastic collapse irrespective of the crack depth or loading condition. The conservatism of the conventional structural integrity assessment was quantified and shown to vary with crack depth and with loading conditions. This research has suggested that failure in a 304(L) stainless steel pipe will be by plastic collapse prior to ductile initiation for a limited range of defects and loading conditions. Further analytical studies and experimental work will be required to demonstrate whether this observation is general for a wider range of defects and loading conditions.

<p>In this work characterisation methods and fuel cell hardwarewere developed for studying the components of the polymerelectrolyte fuel cell (PEFC). Humidifiers and other componentswere tested in order to develop reproducible and reliableexperimental techniques. A set-up for testing larger cells andstacks was developed.</p><p>A new type of polymer electrolyte membrane fuel cell wasdeveloped for laboratory investigations. Current collectormaterial and gas flow channels can easily be modified in thisconstruction. The electrode potentials can be measured at thegas backing layers, thereby allowing measurement of contactresistances. The use of a reference electrode is alsopossible.</p><p>Contact resistances were studied in situ as a function oftime, clamping pressure, gas pressure and current density.Ex-situ measurements were used to validate the in-situ contactresistance measurements. The validity and error sources of theapplied in-situ measurement methods with reference electrodesand potential probes were studied using both computersimulations and experiments.</p><p>An in-house membrane electrode assembly (MEA) productionline was developed. In-house produced MEAs were utilised inboth membrane degradation and mass transport studies.</p><p>The durability testing of PVDF based membranes membranes wasstudied both by fuel cell experiments and ex-situ testing.Raman spectra were measured for used membranes.</p><p>A current distribution measurement method was developed. Theeffect of inlet humidification and gas composition at thecathode side was studied. In addition, two different flow fieldgeometries were studied. The results of current distributionmeasurements were used to validate a PEFC model.</p><p>Methods for characterising gas diffusion layer (GDL)performance by fuel cell testing and ex-situ measurements weredeveloped. The performance of GDL materials was tested withvarying cell compression and cathode humidity. Porosity, poresize distribution and contact angle were determined. Electricalcontact resistance, thermal impedance and gas permeabilitieswere measured at different compression levels.</p><p>Development work on a stack with stainless steel net wascarried out as well as characterisation studies of differentstack components. Thermal impedances and flow fieldpermeability were measured.</p><p>Mass transport limitations in the cathodes were studied byvarying the electrode thickness, partial pressure and humidityof oxygen.</p><p><b>Keywords:</b>polymer electrolyte membrane fuel cell (PEFC),contact resistance, clamping pressure, stainless steel,membrane degradation, current distribution, gas diffusionlayer, stack, thermal impedance, permeability.</p>

Thick-section austenitic stainless steels have widespread industrial applications, especially in nuclear power plants. The joining methods used in the nuclear industry are primarily based on arc welding processes. However, it has recently been shown that the Narrow Gap Laser Welding (NGLW) technique can be used to join materials with thicknesses that are well beyond the capabilities of single pass autogenous laser welding. The heat input for NGLW is much lower than that of arc welding, as are the expected levels of residual stress and distortion. The multi-pass laser welding technique, based on the narrow gap approach, is an emerging welding technology which can be applied to thick-section welds using a relatively low-power laser, but the process is more complicated than autogenous laser welding, since it is necessary to introduce filler wire to narrow gap weld configurations. Despite this complexity, the technique is very promising for improving the penetration capabilities of the laser welding process. However a limited amount of research has been conducted on the development of the NGLW technique; the control and optimization of weld bead quality inside the narrow gap is still an area of weakness. The research described in this thesis involves investigations on NGLW of AISI grade 316L austenitic stainless steel, and the performance of the resulting welds. Design-of-experiments and statistical modelling techniques were employed to understand and optimize the welding process. A statistical model was used in order to understand the significant process parameters and their interactions, allowing improved control of the weld quality in ultra-narrow gap (1.5 mm gap width) welds. The results show a significant improvement in weld quality can be achieved through the use of statistical modelling and multi-variable optimisation. The microstructure characteristics and mechanical properties (e.g. tensile strengths, fatigue, bending strength and fracture toughness) of the NGLW samples were examined and compared with those of other welding techniques - autogenous laser welding and gas-tungsten arc welding (GTAW). The work shows that NGLW of 316L steel sheets up to 20 mm thickness have generally better or comparable mechanical properties than those of GTAW but with much higher welding productivity. The results of detailed investigations of the 2D residual stress distributions, material distortions, and plastic strain characteristics of the NGLW technique are described. The contour method was employed for residual stress evaluation of the NGLW technique, and the results were validated using X-Ray and neutron diffraction measurements. The results were compared with those obtained with GTAW. The results suggest that the longitudinal tensile residual stresses in NGLW joints are 30-40% lower than those for GTAW joints. The influence of the laser power and number of passes for the NGLW technique, on the developed residual stress and plastic strain has been investigated, and the influence of welding strategy and the use of restraint during welding were also investigated. To understand the thermal history in NGLW and its effect on residual stress, finite element analysis was carried out using ABAQUS to numerically model the behaviour of residual stress across the multipass NGLW weld joints. The model has been validated with the experiments using temperature measurements and in terms of residual stresses the model is compared with neutron diffraction and the contour method. There is a very good correlation between the model and experimental results. The influence of both the laser power and welding speed on the induced residual stress during the NGLW process was also investigated using the model. The aqueous, pitting and stress corrosion cracking behaviour of the NGLW joints were investigated, and the results compared to those for GTAW joints under the same conditions. The results show that NGLW joints have better resistance to pitting corrosion than the GTA welds. Preliminary results also suggest that NGLW has better resistance to stress corrosion cracking.

The present work was conducted at Scania CV AB and has as main goal to produce a cast steel guideline. There is a great need to conduct a cast steel guideline, in order to help designers in their process to choose suitable materials and methods to produce lightweight components with higher performance. This work contains information related to mechanical properties, casting processes, castability, machinability, defect characterization, heat treatments, weldability and surface treatments of cast steels. This work was limited to cast steels which could be applied on two specific components of the truck, a bracket which is a structural component of chassis subjected to fatigue and a turbo manifold which is subjected to creep, oxidation, corrosion-, thermal- and mechanical- fatigue. A benchmark search was performed focused on these two components. A characterization of a cast stainless steel turbo manifold prototype was performed in the as-cast state, which included microstructural analyzes and hardness measurements. Besides this initial characterization, a set of heat treatments were conducted, in order to study the possibility to eliminate the initial grain boundary carbides. The main conclusions of this work are that cast steel has potential to be a material choice in many applications due to its wide range of properties. For structural parts, cast steel is advantageous compared with cast iron when for instance welding and high strength combined with high fracture toughness are requirements. For high temperature resistance components, cast steel or more precisely cast stainless steel, is advantageous for service at temperatures &gt;750 ºC,besides its higher price. The annealing heat treatment followed by an aging treatment eliminated most of the grain boundary carbides and increase the hardness through a fine dispersion of carbides in matrix, which can also increase the creep resistance.<br>Examensarbetet utfördes på Scania CV AB med främsta målet att utarbeta en vägledande guide för gjutstål. Det finns ett stort behov av att sammanställa en guideline för gjutstål, med syfte att hjälpa konstruktörer i deras process att välja lämpliga material och metoder för att producera lättviktskomponenter med högre prestanda. Arbetet innehåller information om mekaniska egenskaper, gjutningsprocesser, gjutbarhet, skärbarhet, defektkarakterisering, värmebehandlingar, svetsbarhet, ytbehandling och mycket annat gällande gjutstål. Detta arbete var begränsat till gjutstål som kan tillämpas för två specifika komponenter i lastbilen, en konsol som är en strukturell komponent i chassit som utsätts för utmattning och ett turbogrenrör vilket är en komponent som utsätts för högtemperaturcykler. En benchmark utfördes med fokus på dessa två komponenter. Slutligen gjordes en karakterisering av turbogrenrörsprototypen i rostfritt stål, i det gjutnatillståndet, vilket inkluderade mikroanalyser och hårdhetsmätningar. Förutom den förstakarakteriseringen, utfördes en uppsättning värmebehandlingar för att undersöka möjligheten att eliminera de initiala korngräns-karbiderna. De viktigaste slutsatserna av detta arbete är att gjutstål har potential att bli ett materialval i många applikationer på grund dess breda egenskaper. Konstruktionsdelar i gjutstål är fördelaktiga jämfört med gjutjärn, till exempel vid svetsning och när hög hållfasthet i kombination med hög brottseghet är nödvändigt. För högtemperaturs-komponenter är gjutstål, eller mer exakt, gjutna rostfria stål fördelaktiga för service vid temperaturer &gt;750 ºC, med undantag för dess högre pris. Glödgningsvärmebehandling följt av åldringsbehandling eliminerar de flesta av korngräns-karbiderna och ökar hårdheten genom en fin dispersion av karbider i matrisen, vilket också kan öka krypmotståndet.

Metal surface cleaning is highly required in different fields of modern industry. Nuclear industry seeks for new methods for oxidized surface decontamination, and thermonuclear installations require the cleaning of plasma facing components from tritium-containing deposited layer. The laser ablation is proposed as an effective and safe method for metal surface cleaning and decontamination. The important factor influencing the laser heating and ablation is the in-depth distribution of laser radiation. The model of light propagation in a scattering layer on a metal substrate is developed and applied to analyse the features of light distribution. To simulate the contaminated surfaces, the stainless steel AISI 304L was oxidized by laser and in a furnace. Radioactive contamination of the oxide layer was simulated by introducing europium and/or sodium. The decontamination factor of more than 300 was demonstrated with found optimal cleaning regime. The decreasing of the corrosion resistance was found after laser cleaning. The ablation thresholds of ITER-like surfaces were measured. The cleaning productivity of 0.07 m2/hour∙W was found. For mirror surfaces, the damage thresholds were determined to avoid damage during laser cleaning. The possibility to restore reflectivity after thin carbon layer deposition was demonstrated. The perspectives of further development of laser cleaning are discussed.

No presente trabalho, a conformabilidade do aço inoxinoxidável AISI 201 foi comparada com o aço inoxidável AISI 304. O aço inoxidável AISI 201 é uma liga baixo níquel ligado com manganês e nitrogênio. Nesse estudo a conformabilidade dos dois materiais foi examinada por meio de ensaios tecnológicos como ensaio de tração, determinação da curva de escoamento, determinação do índice de anisotropia, ensaio Erichsen, dureza, composição química, simulação computacional do processo de estampagem e estampagem dos blanks. O aço inoxidável AISI 201 possui propriedades como limite de escoamento e tensão de ruptura superior as do inoxidável AISI 304. Os dois aços possuem uma similaridade na anisotropia. A máxima altura alcançada no momento da fratura pelo ensaio Erichsen também é semelhante para os dois materiais. O aço inox AISI 201 apresenta uma dureza maior que o inoxidável AISI 304. Na composição química os dois aços apresentam elementos fora do especificado, caracterizando um problema de qualidade na fabricação desses aços. A simulação computacional do processo de estampagem apresentou uma redução de espessura na região mais critica, sem comprometer a estampagem do componente. Uma vez estampadas, obteve-se peças sem indícios de trincas, conforme previsto pela simulação computacional. Os resultados desse trabalho sugerem a possibilidade de utilização do aço inoxidável AISI 201 como opção para substituição ao inoxidável AISI 304, tendo uma observação a ser feita quanto aos cuidados na qualidade durante a fabricação do aço para que atenda os padrões exigidos.<br>In this study, the formability of stainless steel AISI 201 was compared to stainless steel AISI 304 stainless steel AISI 201 is a low alloy nickel alloyed with manganese and nitrogen. In this study, the formability of the two materials was examined by means of technological tests such as tensile test, determination of the flow curve, determining the anisotropy index, Erichsen test, hardness, chemical composition, computer simulation of the stamping process and stamping of the blanks. Stainless steel AISI 201 has properties such as yield strength and higher breakdown voltage of the stainless steel AISI 304. The two steels have a similarity in anisotropy. The maximum height reached at the time of fracture by Erichsen test is also similar for the two materials. Stainless steel AISI 201 has a hardness greater than the stainless steel AISI 304. In chemistry the two steels have elements outside the specified, featuring a quality problem in manufacturing these steels. A computer simulation of the printing process showed a reduction in thickness in the most critical region, without compromising the component stamping. Once stamped, gave no broken pieces of evidence as provided by the computer simulation. The findings suggest the possibility of use of stainless steel AISI 201 as an option to replace the stainless steel AISI 304, with a point to be made about the care as during the manufacture of steel that meets the required standards.

A moldagem de pós por injeção (MPI) foi empregada neste trabalho para a fabricação de micro componentes de uma pinça de biópsia, através do desenvolvimento de misturas injetáveis. Utilizou-se a liga de aço inoxidável AISI 316L, liga reconhecidamente biocompatível, para obtenção dos micro componentes. Determinando a quantidade de 39% em volume para fração orgânica das quatro formulações de misturas injetáveis produzidas neste trabalho. Os polímeros estruturais empregados foram o PP, o PEBDL, o PEAD e o PMMA. Como material auxiliar de fluxo foi utilizada a parafina e para agente surfactante, o ácido esteárico. O desenvolvimento do sistema de extração química do polímero auxiliar de fluxo com solvente e posterior extração térmica do ligante em forno convencional e em um reator a plasma foram testados, ainda se empregou estes para testes em sinterização a temperaturas 1200°C, 1250°C e 1300°C. A extração química foi realizada com hexano atingindo 2,41% em massa de material extraído das amostras, após seis horas em um sistema aquecido entre 60°C e 70°C e uma atmosfera de vácuo. As amostras foram testadas química, física, mecânica e eletroquimicamente. Obteve-se os melhores resultados em termos de densificação de 7,05 g/cm³ para as amostras extraídas a plasma e sinterizadas a 1300 °C à vácuo em forno tubular. Isso significa uma densificação de 88,96% comparada a densidade do material comercial cuja a densidade é 7,93 g/cm³. As microdurezas encontradas nas amostras sinterizadas a 1300 °C em um forno convencional obtiveram valores de 208HV se mostrando maiores do que os 165HV obtido de um material maciço fabricado pelo extrusão e comercialmente vendido. Encontrou-se a dureza de 55HRB nas amostras processadas a 1300 °C, devido a presença de poros em componentes sinterizados. Nos componentes maciços foram medidos a dureza de 88HRB que foi maior que os resultados das amostras sinterizadas. As análises metalográficas mostraram um tamanho de grão variando entre, 30 e 50μm, se comparado ao tamanho de partícula médio do D90 de foi de 8,59 μm, se estima que este aumento foi entorno de três vezes e meia. Os testes químicos revelaram que a extração térmica em reatores a plasma melhoram significativamente os níveis de C, N, H e S quando comparados ao processo de extração térmica em forno convencional. A redução dos níveis de carbono residual, resultaram em diminuição do carboneto de cromo nas amostras, provocando uma menor corrosão. As amostras sinterizadas a 1200 °C a plasma apresentaram os melhores resultados de corrosão.<br>The powders injection molding (PIM) was used in this research, with objective to manufacture micro component, for application in biopsy forceps being developed injectable mixtures . It was used the powder stainless steel AISI 316L alloy, material biocompatible, to obtain the micro components. Through tests was determining the amount optimal volume in 39 % for the organic fraction of the four formulations of injectable mixtures produced in this research. The structural polymers used were PP , LLDPE , HDPE and PMMA . The paraffin was used as auxiliary material flow, the surfactant agent employed that was stearic acid . The development of chemical debiding and the thermal extraction for binder system, was used the conventional furnace and in a plasma reactor were tested also be employed for these tests sintering temperature 1200 ° C , 1250 °C and 1300 °C. Chemical extraction was performed with hexane achieving 2.41 % by extracted mass of sample material, after six hours in a heated system between 60 °C and 70 °C and a vacuum atmosphere. The samples were tested analysis by chemical , physical , mechanical and electrochemical.If it obtained the best results in terms of densification of 7.05g/cm ³ for plasma samples extracted and sintering at 1300 °C in vacuum tube furnace . This means densification of 88.96 % compared to the density of commercial material whose density is 7.93 g/cm ³ . The microhardness found in the samples sintered at 1300°C in a conventional furnace obtained 208HV microhardness showing larger than the commercial 165HV. Found that the HRB hardness of 55 in the samples processed at 1300 °C, due to the presence of pores in sintered parts. In the extruded components were measured hardness of 88HRB which was higher than the results of the sintered samples. The metallographic analysis showing a grain size ranging between 30 and 50μm , compared to the average particle size D90 was 8,59 microns is estimated that this increase was around three and half times . The chemical tests revealed that the thermal plasma extraction reactor significantly improve the levels of C, N , H and S compared to the process heat extraction in a conventional furnace . The residual carbon levels significantly improved, which helps to avoid the formation of chromium carbides , which aumnetou corrosion resistance . The best results in terms of corrosion were found for the samples sintered at 1200 ° C the plasma.

碩士<br>國立虎尾科技大學<br>材料科學與工程系材料科學與綠色能源工程碩士在職專班<br>106<br>This paper was devoted to non-destructive tests for the weldment of vacuum chamber component, and the weld microstructures, hardness and electrochemical behavior were evaluated in as-welded condition. SUS304 austenitic stainless steel plates were joined in double-sided groove welds using gas tungsten arc welding method and 308L filler wire was used for the joints. Experimental results showed that the high quality welded joints were achieved by multi-pass gas tungsten arc welding with filler wire addition. It was confirmed by results of visual, phased array ultrasonic testing and helium leak testing. Microstructure analyses revealed the fusion zone was typically dendritic with lathy ferrite morphology. The transition zone between base material and weld seam it was found that the grains were oriented towards the welding center and the dendritic structure. Micro-hardness profiles in welded joints showed increasing of the hardness in the fusion zone, which could be attributing to a finer microstructure that is induced by rapid cooling. X-ray diffraction results showed only the single phase of austenite was identified in the base metal and the presences of austenite and delta ferrite in the welds were observed. The lower corrosion resistance of the fusion zone compared to base metal was because delta ferrite in it.

碩士<br>國立交通大學<br>機械工程系所<br>93<br>The development of High-Entropy alloys has aroused considerable interest recently. Many investigations have been conducted on the microstructures, mechanical properties, corrosion resistance, heat treatment, thin film development, and phase identifications. These newly developed alloys have good corrosion and wear resistance, high-temperature mechanical properties, and specially physical and chemical properties with nanostructure. This experimental research project aimed at the investigation of weldability testing and microstructure analysis of Gas Tungsten Arc Welding (GTAW or TIG) weldments of these high-entropy alloys. In this study, a new welding material was developed to make a decent dissimilar metal welding joint of this alloy with other stainless steels. Superalloys 230 and 718 were also used as the filler metal. A series experiments included micro-hardness measurements, tensile testing, SEM and EDS analysis were conducted in this investigation. The experimental results have lead to the following conclusions： 1.The weldment with high-entropy filler metal has the best mechanical strength and ductility. 2.The tensile strength of dissimilar metal joint weldment of high-entropy alloy and stainless steel 304 is greater than that of stainless steel 304. 3.High-entropy alloy can be used as welding filler metal for the joining of same type high-entropy alloy.