Please read the abstract in the section, 00front, of this document / Thesis (PhD)--University of Pretoria, 1987. / Materials Science and Metallurgical Engineering / PhD / unrestricted

A dissertation submitted to the University of the Witwatersrand in fulfillment of the degree of Master of Science, Engineering. Johannesburg, 1995. / Some authors define weldebility as the ability of a material to maintain its integrity, that is, its microstructure, corrosion and mechanical properties after welding. If such a stringent criteria is used to adequately describe the weldability of a material, then there would be but a few alloys which could be deemed weldable. As such this definition was found to be much to restrictive, and the author, has defined the term 'weldability' as the ability of a material to retain its corrosion and mechanical properties, such that the integrity of an as-welded structure under a particular service environment would be maintained to within acceptable limits. With this definition in mind the weldability of experimental low-nickel duplex stainless steels containing chromium, manganese and nitrogen were assessed. This assessment was based on the corrosion and mechanical properties of these alloys which were manual metal arc welded and plasma arc welded using a range of heat inputs. The results of these tests showed that the wrought and spun cast alloys are readily weldablility for the range of heat inputs considered. As a comparison to the welding charactristics of the high nitrogen alloys, a commercially available high carbon containing spun cast duplex stainless steel, MP36, alloy was used as a reference material. This alloy proved invaluable in that, not only was it possible to show that this alloy faked poorly in comparison with the high nitrogen containing alloys, but the effect of nitrogen as an interstitial element in welded stainless steels could be compared with that of carbon. The results of the latter evaluations showed that nitrogen, unlike carbon, does not have a detrimental effect on the corrosion or mechanical properties of these alloys, provided it is kept below the solubility limit of 'the stainless steel. The appearance of the microstructures of the high nitrogen containing alloys and the reference alloy in the solution annealed condition, were maintained after welding, with no rampant ferrite phase growth or extensive precipitation in the heat affected zone for the range of {Abbreviated Abstract. Open document to view full version} / MT2017

A new pre-weld heat treatment was developed recently for IN 738 superalloy. Therefore, the research described in this master’s thesis was to study the laser weldability improvement of the alloy which had undergone the new heat treatment, FUMT and the results were compared to an existing pre-weld heat treatment, solution heat treatment (SHT). Also, thermomechanical fatigue (TMF) behavior of the welded alloy was investigated. The results showed that IN-738 welded in FUMT condition had about 70% reduction in weld cracking compared to SHT treated alloy. TMF tests showed that at higher strain ranges, the TMF life of the samples of the alloy welded in FUMT condition is comparable to unwelded samples, while at lower strain ranges, welded samples of the alloy in FUMT condition has a higher TMF life than unwelded samples. This shows that welding IN 738 superalloy in FUMT does not degrade the TMF performance of the alloy.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Thomas David Burleigh. / M.S.

In recent years, nanostructured and amorphous metals have become more prominent in scientific research. Their unique characteristics and their vastly superior mechanical properties have lead to emerging technical applications however the use of these materials is only in its infancy. To further growth the industrial applications for these advanced materials, joining processes capable of maintaining the unique aspects of the microstructure are required. / Joining of two beveled plates has been accomplished by use of the Cold Spray process. This process uses a converging diverging nozzle to accelerate micron sized powder towards a substrate. The strength of the resulting joint has been compared to freeforms made of powder of the same composition. No significant difference was observed in the mechanical properties between the freeforms and the weldments and examination of the fracture surface showed that the strength of the interface is higher than the strength of the freeform itself. / A weld repair experiment has also been performed where the ElectroSpark Deposition process (ESD) has successfully been used to transfer amorphous material from an electrode to an amorphous substrate without crystallizing either material. This result is of crucial importance as it signifies that these extremely expensive and heat sensitive materials can be repaired when in-service wear causes damage. This process, due to its inherently fast cooling rate, has also successfully been used to transform a crystalline AlCoCe alloy into an amorphous deposit atop both amorphous and crystalline substrates.

No description available.

IN-738 LC, a precipitation hardened nickel based superalloy, containing substantial amounts of Al + Ti contents, is very difficult to weld due to its high susceptibility to HAZ cracking, during welding via conventional fusion welding techniques and subsequent PWHT. The cracking is mainly intergranular in nature and associated with liquation of secondary solidification products (such as MC carbides,  -  eutectic phases), and solid state reaction products ( precipitate particles) that are present along the grain boundaries in the pre-weld material. The current research was to find effective ways to improve weldability of IN-738 LC. Laser welds were produced autogenously on conventionally solidified (CS) and directionally solidified (DS) polycrystalline, and single crystal (SC) IN-738 LC subjected to two preweld heat treatments. Weldability was assessed by measuring the total crack lengths in HAZ. The influence of grain boundaries and heat treatment on extent of cracking in IN-738 LC was studied.

Bibliography: leaves 191-198. / xxi, 201 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the mechanisms controlling the dilution, geometry and wear performance of weld- deposited high-chromium white iron surface layers. Focuses on layers deposited by mechanised flux-cored-arc welding, as this process achieves higher deposition rates than manual-metal-arc welding and affords a greater degree of control over individual welding variables. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1999

This thesis work is mainly focused on the processes involved in manufacturing of aircraft engine components. The processes are especially about welding and welding methods. The basics of welding and the thesis support has been taken from the GKN Aerospace Sweden AB, a global aerospace product supplier.  The basic objective of this thesis work is to improve the usability of an automation system which is developed for evaluating the weldability of a part. A long run maintainability aspect of this automation system has been considered. The thesis work addresses the problems arising during the usage of a computerised automated system such as process transparency, recognisability, details traceability and other maintenance aspects such as maintainability and upgradability of the system in the course of time. The action research methodology has been used to address these problems.  Different approaches have been tried to finding the solution to those problems. A rule based manufacturability analysis system has been attempted to analyse the weldability of a component in terms of different welding technics. The software “Howtomation” has been used to improve the transparency of this analysis system. User recognisability and details tractability have been taken into account during the usage of a ruled based analysis system. The system attributes such as maintainability, upgradability, adaptiveness to modern welding methods has been addressed. The system suitability for large scale analysis has been considered.

Orientador: Vicente Afonso Ventrella / Resumo: Incluído na família dos Ferríticos, o aço Inox AISI 430 é um material importante sob os aspectos econômico e tecnológico, onde, atualmente passaram a ser utilizados cada vez mais nas indústrias de diversas áreas, como: automobilística, química e de aparelhos domésticos, perante a grande possibilidade de aplicação deste material. Em geral, esse material apresenta uma baixa sᴏldabilidade, particularmente se cᴏmparados cᴏm os austeniticos, pᴏis a sᴜa sᴏlda é caracterizada pᴏr dutilidade e tenacidade baixas além de sensibilidade à cᴏrrosão intergranᴜlar. A soldagem a laser desse material faz com que ocorra um crescimento do grão, tendo, entretanto, grãos colunares, com uma estrutura de granᴜlação grᴏsseira, apresentando uma rede martensita jᴜnto aᴏs contorno de grão, apresentando uma ZAT (zona afetada termicamente) perdendo sua resistência nas propriedades mecânicas. Este trabalho tem por objetivo avaliar as características do cordão de solda, realizando a análise da influência do processo de soldagem utilizando o laser pulsado Nd:YAG aplicado em soldas de chapas de aço inoxidável ferrítico AISI 430, com 1,0 mm de espessura, observando as características mecânicas e microestruturais da junta soldada. Por meio da variação da taxa de sobreposição do cordão de solda se fez uma soldagem em junta de topo, com seis condições de amostras, sendo estas de valor fixo de energia de soldagem em 10 Joules, com largura temporal em 5 ms, velocidade de soldagem em 1 mm/s, tendo alteração apenas ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Included in the Ferritic family, AISI 430 stainless steel is an important material in terms of economics and technology, where, today, they are increasingly used in industries such as: automobile, chemical and household appliances, possibility of applying this material. In general, such material has a low solvency, particularly if cured as austenitic, because the latter is characterized by low ductility and toughness in addition to sensitivity to intergranular corrosion. The laser welding of this material causes a growth of the grain to occur, however, having columnar grains with a gross granulation structure, presenting a martensite network along the grain boundary, presenting a ZAT (thermally affected zone), losing its resistance mechanical properties. This work aims to evaluate the characteristics of the weld bead, performing the analysis of the influence of the welding process using the pulsed Nd: YAG laser applied in welds of AISI 430 ferritic stainless steel sheets, 1.0 mm thick, observing the mechanical and microstructural characteristics of the welded joint. By means of the variation of the overlapping rate of the weld bead was made a top joint welding with six sample conditions, these being of fixed value of welding energy in 10 Joules, with time width in 5 ms, welding speed in 1 mm / s, with only frequency changes ranging from 1.8 to 10 Hz, thus giving rise to different overlapping rates, in which argon gas protection was obtained, with a flow rate of 15 l / min. Th... (Complete abstract click electronic access below) / Mestre