Characterization of Phases in a Nickel Base Superalloy PDF Download

Author: Shanker, Kartik
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Jinghao Xu
Publisher: Linköping University Electronic Press
ISBN: 9179297269
Category :
Languages : en
Pages : 63

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Nickel-based superalloys, an alloy system bases on nickel as the matrix element with the addition of up to 10 more alloying elements including chromium, aluminum, cobalt, tungsten, molybdenum, titanium, and so on. Through the development and improvement of nickel-based superalloys in the past century, they are well proved to show excellent performance at the elevated service temperature. Owing to the combination of extraordinary high-temperature mechanical properties, such as monotonic and cyclic deformation resistance, fatigue crack propagation resistance; and high-temperature chemical properties, such as corrosion and oxidation resistance, phase stability, nickel-based superalloys are widely used in the critical hot-section components in aerospace and energy generation industries. The success of nickel-based superalloy systems attributes to both the well-tailored microstructures with the assistance of carefully doped alloying elements, and the intently developed manufacturing processes. The microstructure of the modern nickel-based superalloys consists of a two-phase configuration: the intermetallic precipitates (Ni,Co)3(Al,Ti,Ta) known as γ′ phase dispersed into the austenite γ matrix, which is firstly introduced in the 1940s. The recently developed additive manufacturing (AM) techniques, acting as the disruptive manufacturing process, offers a new avenue for producing the nickel-based superalloy components with complicated geometries. However, γ′ strengthened nickel-based superalloys always suffer from the micro-cracking during the AM process, which is barely eliminated by the process optimization. On this basis, the new compositions of γ′ strengthened nickel-based superalloy adapted to the AM process are of great interest and significance. This study sought to design novel γ′ strengthened nickel-based superalloys readily for AM process with limited cracking susceptibility, based on the understanding of the cracking mechanisms. A two-parameter model is developed to predict the additive manufacturability for any given composition of a nickel-based superalloy. One materials index is derived from the comparison of the deformation-resistant capacity between dendritic and interdendritic regions, while another index is derived from the difference of heat resistant capacity of these two spaces. By plotting the additive manufacturability diagram, the superalloys family can be categorized into the easy-to-weld, fairly-weldable, and non-weldable regime with the good agreement of the existed knowledge. To design a novel superalloy, a Cr-Co-Mo-W-Al-Ti-Ta-Nb-Fe-Ni alloy family is proposed containing 921,600 composition recipes in total. Through the examination of additive manufacturability, undesired phase formation propensity, and the precipitation fraction, one composition of superalloy, MAD542, out of the 921,600 candidates is selected. Validation of additive manufacturability of MAD542 is carried out by laser powder bed fusion (LPBF). By optimizing the LPBF process parameters, the crack-free MAD542 part is achieved. In addition, the MAD542 superalloy shows great resistance to the post-processing treatment-induced cracking. During the post-processing treatment, extensive annealing twins are promoted to achieve the recrystallization microstructure, ensuring the rapid reduction of stored energy. After ageing treatment, up to 60-65% volume fraction of γ′ precipitates are developed, indicating the huge potential of γ′ formation. Examined by the high-temperature slow strain rate tensile and constant loading creep testing, the MAD542 superalloy shows superior strength than the LPBF processed and hot isostatic pressed plus heat-treated IN738LC superalloy. While the low ductility of MAD542 is existed, which is expected to be improved by modifying the post-processing treatment scenarios and by the adjusting building direction in the following stages of the Ph.D. research. MAD542 superalloy so far shows both good additive manufacturability and mechanical potentials. Additionally, the results in this study will contribute to a novel paradigm for alloy design and encourage more γ′-strengthened nickel-based superalloys tailored for AM processes in the future.

Author: Ricky Lee Whelchel
Publisher:
ISBN:
Category : Electric resistance
Languages : en
Pages :

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Nickel-base superalloys obtain high temperature mechanical properties through formation of precipitate phases formed via heat treatment. The precipitate microstructure evolves with heat treatment or thermal exposure, which can lead to degrading mechanical properties. This project focuses on the use of electrical resistivity as a non-destructive testing method to monitor the precipitate phase in Waspaloy (a polycrystalline nickel-base superalloy). The evolution of the precipitate microstructure is characterized throughout the volume of the specimens using both small angle neutron scattering (SANS) and ultra small angle X-ray scattering (USAXS) measurements. These measurements are also aided by microscopy and X-ray diffraction measurements.

Author: Charles Hubert Smith
Publisher:
ISBN:
Category : Dispersion strengthening
Languages : en
Pages : 346

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Author: Robert L. Dreshfield
Publisher:
ISBN:
Category : Heat resistant alloys
Languages : en
Pages : 36

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Sigma-free, moderately, and very sigma prone cast IN-100 were exposed at 1550' F (843' C) for 250 and 2500 hours to permit sigma to form. As sigma increased, rupture life, tensile strength and ductility decreased. Yield strength at room temperature increased after exposure for 250 hours. Exposure times of 2500 hours caused the yield to approach or fall below the as cast values. Sigma isothermal transformation curves were prepared for wrought and cast IN-100 having essentially the same compositions. Wrought material exposed in a stress gradient at 1550' F (843' C) was examined for a stress effect on sigma formation.

Author: C. H. Lund
Publisher:
ISBN:
Category : Heat resistant alloys
Languages : en
Pages : 54

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Category :
Languages : en
Pages :

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Welding is important for economical reuse and reclamation of used and failed nickel-base superalloy blades, respectively[1]. Solidification and solid state decomposition of[gamma] (Face Centered Cubic, FCC) phase into[gamma][prime] (L1[sub 2]-ordered) phase control the properties of these welds. In previous publications, the microstructure development in electron beam welds of PWA-1480 alloy[2] and laser beam welds of CMSX-4 alloy[3] were presented. These results showed that the weld cracking in these alloys were associated with low melting point eutectic at the dendrite boundaries[1,2]. The eutectic-[gamma][prime] precipitation was reduced at rapid weld cooling rates and the partitioning between[gamma]-[gamma][prime] phase was found to be far from equilibrium conditions[3,4]. This observation was related to diffusional growth of[gamma][prime] precipitate into[gamma] phase. Subsequent to the above work, the precipitation characteristics of[gamma][prime] phase from[gamma] phase were evaluated during continuous cooling conditions[5]. The results show that the number density of[gamma] precipitates increased with an increase in cooling rate. However, the details of this decomposition and also the fine-scale elemental partitioning characteristics between[gamma]-[gamma][prime] were not investigated. In this paper, the precipitation characteristics of[gamma][prime] from[gamma] during continuous cooling conditions were investigated with transmission electron microscopy, and atom probe field ion microscopy. In addition, thermodynamic and kinetic models were used to describe microstructure development in Ni-base superalloy welds.

Author: John M. Merrill
Publisher:
ISBN:
Category : Fracture mechanics
Languages : en
Pages : 140

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Author: Loeïz Nazé
Publisher: Elsevier
ISBN: 0128193581
Category : Technology & Engineering
Languages : en
Pages : 612

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Nickel Base Single Crystals Across Length Scales is addresses the most advanced knowledge in metallurgy and computational mechanics and how they are applied to superalloys used as bare materials or with a thermal barrier coating system. Joining both aspects, the book helps readers understand the mechanisms driving properties and their evolution from fundamental to application level. These guidelines are helpful for students and researchers who wish to understand issues and solutions, optimize materials, and model them in a cross-check analysis, from the atomistic to component scale. The book is useful for students and engineers as it explores processing, characterization and design. Provides an up-to-date overview on the field of superalloys Covers the relationship between microstructural evolution and mechanical behavior at high temperatures Discusses both basic and advanced modeling and characterization techniques Includes case studies that illustrate the application of techniques presented in the book

Author:
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Category :
Languages : pt-BR
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Este trabalho consiste na caracterização da fase gama linha em superligas deníquel através do processamento e análise digital de imagens. Amostras de umasuperliga de níquel foram submetidas a 10 tratamentos térmicos diferentes. Apóso tratamento térmico, estas amostras foram preparadas para avaliaçãometalográfica e imagens da microestrutura foram adquiridas no microscópioeletrônico de varredura (MEV). A fase gama linha presente no material foisegmentada e posteriormente medida através do processamento digital deimagens. Foram analisadas 429 imagens, o que gerou medidas de mais de 225,000partículas. Foi medida a fração de área ocupada pelas partículas de gama linha, aquantidade de partículas por imagem, a área de cada partícula e a razão deaspectos das partículas. Uma análise estatística dos resultados foi realizada. Osresultados mostraram menor concentração e maior tamanho de gama linha com oaumento da temperatura, conforme era esperado. O uso de análise digital deimagens permitiu obter medidas com altíssima confiabilidade, uma vez que a altavelocidade de análise permite uma amostragem muito superior às técnicastradicionais de caracterização microestrutural.