Download or read book Characterization and Deformation Behavior of Microstructural Gradients in the Low Solvus High Refractory LSHR Nickel Base Superalloy written by Samuel Joshua Morris Kuhr and published by . This book was released on 2016 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Alloy Design and Characterization of Strengthened Nickel based Superalloys for Additive Manufacturing written by Jinghao Xu and published by Linköping University Electronic Press. This book was released on 2021-01-28 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Microstructural Evolution and Deformation Mechanisms in Nickel base Super Alloys written by Hyo-jin Song and published by . This book was released on 2010 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nickel-base superalloys are used at high temperature applications in aerospace and power generation. The objective of present work is to gain a better understanding of microstructural evolution and deformation mechanisms in Nickel-base superalloys. The microstructure of the Nickel base superalloy is basically composed of gamma matrix with eta, delta, gamma prime or gamma double prime/or both, carbides and nitrides. Cold working of IN 718 and Waspaloy to 50% reduction led to an increase in hardness. This hardening was related to the continuous increase in dislocation density in both alloys. Cold working of IN 718 to levels of 10% and higher also led to shearing of the gamma double prime precipitates present initially, leading to their dissolution and the redistribution of the alloying elements into the matrix. Shot peening of both alloys introduces near surface compressive residual stresses and a significant increase in the surface and near-surface hardness to a distance of ~200-400 [mu]m in both alloys. Shot peening of both alloys followed by aging at 900°C quickly led to a large drop in hardness to near that of the bulk material. Aging shot peened the IN 718 at 700°C led to an increase in the hardness throughout the sample. Microstructural characterization revealed that this hardening is related to the formation of new precipitates of gamma prime or gamma double prime or both within the gamma matrix. Aging shot peened Waspaloy at 700°C led to an increase or decrease at near surface region at short time, depending on the Almen intensity. Microstructural characterization shows that these changes are related to partial reduction in % cold work by recrystallization and/or new gamma prime precipitation, depending on the Almen intensity. The hardening, microstructural evolution and stress rupture behavior of IN 740 were studied. Aging of the IN 740 alloy led to significant hardening due to the gamma prime precipitation. The gamma prime coarsening in aged and tensile tested and stress rupture tested IN740 alloy was observed to follow the LSW theory. Gamma prime coarsening was promoted by the applied stress and accelerated between 750 and 800°C. Applied stress was also found to significantly enhance the eta phase formation. Various models for strengthening in Ni-base superalloys were considered and their contributions to strength following aging were calculated utilizing the experimentally measured gamma prime sizes and volume fractions. Good agreement between the calculated and experimentally measured yield strengths was obtained. Based on these calculations and characterization of the deformation microstructure in the aged and tensile-tested samples, it was concluded that apart from solid solution strengthening, the main strengthening contributions from the gamma prime precipitates is associated with precipitate shearing involving either weak pair dislocation coupling or strong pair dislocation coupling/ or both at 700°C for 100h, strong pair dislocation coupling following aging at 700°C for 1000, 3000h and 750°C for 100, 1000h, strong pair coupling or Orowan process/or both following aging at 750°C for 3000h and 800°C for 100h, and mainly Orowan process following aging at 800°C for 1000 and 3000h.

Download or read book Nickel Base Single Crystals Across Length Scales written by Loeïz Nazé and published by Elsevier. This book was released on 2021-09-28 with total page 612 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Understanding the Hot Working Behavior of a Ni Base Superalloy XH 67 Via Processing Map Approach written by N. T. B. N. Koundinya and published by . This book was released on 2020 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hot deformation behavior of nickel-based superalloy XH 67 (Ni-18.5Cr-4.5Mo-4.5W-3.0Fe-2.5Ti-1.2Al) was investigated in the temperature range of 900Degree C-1,200Degree C and in the strain rate range of 10 -3 -10 s -1 . A processing map was generated from the flow stress data. Detailed postdeformation microscopy was carried out to understand the microstructural evolution during hot deformation. Correlation of the kinetic analysis together with microstructural characterization studies was accomplished to identify the rate controlling mechanism. An increase in the fraction of , 3, , , , boundaries is observed with an increase in the strain rate at 1,150Degree C. In the temperature range of 1,100Degree C-1,200Degree C, discontinued dynamic recrystallization has been identified as the major softening mechanism. Based on the critical analysis of the mechanical data together with microstructural analysis, the safe hot working regime for the XH 67 alloy is established to have a temperature range of 1,100Degree C-1,200Degree C and a strain rate range of 10 -3 to 5-10 -2 s -1.

Download or read book Superalloys 2012 written by Eric S. Huron and published by John Wiley & Sons. This book was released on 2012-10-02 with total page 952 pages. Available in PDF, EPUB and Kindle. Book excerpt: A superalloy, or high-performance alloy, is an alloy that exhibits excellent mechanical strength at high temperatures. Superalloy development has been driven primarily by the aerospace and power industries. This compilation of papers from the Twelfth International Symposium on Superalloys, held from September 9-13, 2012, offers the most recent technical information on this class of materials.

Download or read book The Effects of Microstructure and Strain Rate on the Deformation Behavior of the Nickel base Superalloy Rene 95 at 650 C written by Edie A. Oja and published by . This book was released on 1994 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of a Nickel base Superalloy Through Electrical Resistivity microstructure Relationships Facilitated by Small Angle Scattering written by Ricky Lee Whelchel and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book On the Path dependent Microstructure Evolution of an Advanced Powder Metallurgy Nickel base Superalloy During Heat Treatment written by Nicholas J. Krutz and published by . This book was released on 2020 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: The realization of advanced alloy compositions in service relies on a thorough understanding of metallurgical processing variables. Within this work, the gamma prime precipitation of an advanced powder metallurgy nickel-base superalloy during controlled cooling from supersolvus temperatures is compared to prior alloy generations using a complement of characterization and modeling approaches. The on-cooling precipitation of the alloy is studied and characterized to calibrate a multi-scale precipitation model. The proposed framework incorporates a computationally efficient addition to the mean-field modeling approach that increases its ability to model dynamic, multi-modal gamma prime burst events. The gamma prime size predicted by the model shows good agreement with experimental results. The precipitation calculation is applied to the element integration points of a continuum Finite Element heat conduction simulation, where the latent heat generated from the precipitation is accounted for. The results are compared to experimental findings and indicate potential use of the model for evaluating precipitation effects at multiple length scales. The lattice misfit evolution of two commercial PM nickel superalloys during cooling from supersolvus temperatures is also characterized, using in-situ synchrotron X-Ray Diffraction (XRD). The diffraction pattern deconvolution necessary for quantifying misfit was accomplished by combining observation of the superlattice peak intensities with thermodynamic modeling to quantify the intensity relationship between the overlapping phases. The misfit from the XRD measurements was compared to the Scanning Electron Microscopy observations of gamma prime particle shapes for a subset of the experimental conditions. The trend of measured misfit agreed with the microstructural characterization. Time-resolved observations of the on-cooling lattice parameter suggest that lower-temperature changes to the peak intensity characteristics coincide with low misfit magnitudes and a plausible connection to gamma prime burst events. Variation in cooling rate for this alloy and its predecessors shows a tendency for unstable precipitate growth with slower rates. To better understand the effect of precipitate morphology on defect interaction, a series of lab heat treatments of varied cooling rates were carried out and the mechanical response characterized. A phase-field based approach is used to simulate the growth instability of gamma prime precipitates during cooling and compared to post-mortem characterization using serial sectioning and reconstruction. Phase-field modeling is then used to interrogate the interaction of the particle morphology with planar dislocation evolution. It was determined that the incipient stages of particle evolution are dictated by interface growth instability more so than elastic anisotropy effects. Planar deformation in the presence of more evolved particles tended to promote Orowan looping while smaller particles with smaller gamma channel widths showed a tendency for stacking fault formation under the conditions characterized. To further understand precipitate morphology on properties, a stand-alone spectral-based microelasticity model is employed to predict the stress field around the particles. First order deformation assumptions are assessed to understand the effect of the microelastic stress field interacting with dislocations. By comparing the fields of varied precipitate morphologies, it is observed that the magnitudes and spatial distribution of the stress tensor components vary by morphology and may contribute to differences from a defect interaction standpoint.

Download or read book Characterization and Modeling of Microstructure Development in Nickel base Superalloy Welds written by and published by . This book was released on 1999 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Superalloys written by Roger C. Reed and published by Cambridge University Press. This book was released on 2008-07-31 with total page 363 pages. Available in PDF, EPUB and Kindle. Book excerpt: Superalloys are unique high-temperature materials used in gas turbine engines, which display excellent resistance to mechanical and chemical degradation. This book introduces the metallurgical principles which have guided their development. Suitable for graduate students and researchers, it includes exercises and additional resources at www.cambridge.org/9780521859042.

Download or read book A Microstructural Characterization of Boron containing Melt Spun Ni base Superalloys written by Helen Segal and published by . This book was released on 1983 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of Microstructure Evolution of Nickel Base Superalloys in Support of the Development of a Grain Growth Model written by Daniel Richard Corwin and published by . This book was released on 2007 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: I would like to thank Dr. Michael Mills, my adviser, for providing excellent support and guidance throughout this work. I'd also like to thank Eric Payton for his contributions and advice regarding practically all aspects of this project. Close collaboration with Dr. Yunzhi Wang, Gang Wang, and Ning Ma has been a very beneficial experience that has given me a valuable understanding of microstructure modeling. I am also very appreciative of the help received from Peter Sarosi, Libor Kovarik, and Ray Unocic regarding the transmission electron microscopy performed in this research. I wish to thank Dave Mourer, Deb Whitis, and Dan Wei at GE Aviation for providing guidance and direction in addition to making this research opportunity possible. Thanks to Ron Tolbert for helping procure the needed materials. I am grateful for the superior quality of the Campus Electron Optics Facility at OSU, and I'd like to specifically thank Cameron Begg and Henk Colijn for their assistance with SEM and TEM operation. This research was funded by GE Aviation.

Download or read book Microstructure and Mechanical Properties of Nickel based Superalloy Hastelloy X Fabricated by Laser Powder Bed Fusion written by Oscar Sanchez Mata and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Additive manufacturing (AM), particularly laser powder bed fusion (LPBF) has been used to process Ni-based superalloys as an alternative to traditional manufacturing methods. However, they can be prone to cracking when fabricated through LPBF. Hastelloy X (HX) is a solid solution strengthened (SSS) alloy that although being categorized as readily weldable, suffers from cracking during LPBF. This document presents a study of crack-free LPBF HX microstructures, their behaviour after post-processing and their relationship with mechanical properties. Moreover, the application of unique microstructural features that result from LPBF processing to scale from bulk to more complex parts and tailor mechanical properties is documented. Crack-free HX fabricated through LPBF from powder having a standard chemical composition is reported. Electron backscatter diffraction (EBSD) analysis evidenced columnar grains parallel to the building direction (BD). The columnar sub-grain solidification microstructure was found to be finer than reported elsewhere. Mo-enriched carbides (~50 nm), were identified along interdendritic regions. The crack-free condition was maintained after heat treatment at 1177 °C for 1 h and its microstructure was analyzed. Dense and crack-free specimens were printed in both horizontal and vertical orientations. Samples were analyzed in as-built (AB), hot isostatic pressing treatment (HIP), and conventional heat treatment (HT) conditions. Tensile testing was done at room and elevated temperature (RT, ET = 750°C). AB samples showed columnar grains and a partial fiber texture aligned with the BD, which was reduced after HIP and HT. Mo and Cr carbides were found at RT which grew after ET. AB samples displayed high ultimate tensile strength (UTS) up to 924 ± 10 MPa, while strength values remained close to a reference HX wrought alloy after HIP and HT. Although lower ductility was observed for AB samples at ET, elongation was improved after HIP and HT. Strength and elongation comparable to that of the wrought alloy at RT can be obtained by only performing conventional HT, without the need of HIP. Dense and crack-free LPBF HX thin cylindrical struts with diameters from 0.25 to 2 mm were built. Their crystallographic texture transitioned from a 110 || BD fiber texture (2 mm), to a single crystal 110 || BD (0.25 mm). The size of cellular sub-grain microstructure increased as strut diameter decreased and was linked with an inverse trend in microhardness, which was the highest in the 2 mm strut due to a smaller cell size. Lower hardness in regions close to the strut edges was also related to a larger observed cell size. From tensile testing, elongation was measured at 35-50%. Deformation twinning and lattice rotation after testing were observed. Differences in strength between struts of different diameter were discussed. Fractography analysis confirmed the ductile fracture behavior. Finally, the unique strong crystallographic texture behaviour of LPBF HX was studied in more detail. Tensile properties at RT were investigated along the 100, 110, and 111 crystallographic orientations. Tensile behavior was highly dependent on crystallographic orientation and showed a good combination of strength and ductility when compared with other LPBF HX. EBSD analysis after fracture revealed deformation twinning in 110 and 111 samples, but not in 100. Crystallographic orientation had an impact on the effective stacking fault energies and on the critical stress for deformation twinning. The latter was near or below the yield strength (YS) value for 110 and 111, while it was above the UTS of the 100 orientation. The YS value of 111 (807 ± 28 MPa) was higher than for 100 (693 ± 8 MPa) and 110 (648 ± 13 MPa). Results suggest that deformation twinning can occur in SSS Ni-based superalloys at RT. In contrast to the 100 and 111 orientations, rotation of the lattice after deformation was found for the 110 direction"--

Download or read book Microstructural Responses of a Nickel Base Cast IN 738 Superalloy to a Variety of Pre weld Heat treatments written by Anurag Thakur and published by . This book was released on 1998 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Softening Mechanisms and Microstructural Instabilities of Nickel During High Temperature Low Cycle Fatigue written by Shuhrong Chen and published by . This book was released on 1989 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Multiscale Approach of the Stress assisted Oxidation of Nickel based Superalloys written by Charles Romain and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nickel-based superalloys are widely used for structural applications at high and intermediate temperatures in severe atmospheres. Environmentally assisted degradation, i.e. oxidation and corrosion, alters not only the surface of the materials, but also their core properties due to a selective and progressive consumption of the reactive elements involved in the surface degradation processes. The material in a shallow region beneath the reactive surface subsequently shows a gradient in chemical composition, microstructure and physical properties. Despite the negligible scale of those gradients (from micrometers to hundreds of micrometers beneath the surface) relative to the dimensions of the structural component, the variability in mechanical behavior within the gradient often drives premature damage and progressive failure of the component. In order to quantify these developments, micromechanical characterization of the mechanical properties of gradient materials is important. Due to the high variability of mechanical properties within graded materials, micromechanical characterization techniques are required. Materials are characterized in aged and pre-oxidized at the temperature of 700°C. These same characterizations are also carried out at 800°C, in order to exacerbate the consequences of oxidation and to increase this gradient of properties at iso-duration of heat treatment. The mechanical characterization of ultrathin specimens (a few tens of micrometers thick) in tension and fatigue is carried out with macroscopic monitoring by image correlation. In addition to the macroscopic values, a specific investigation of the surface for full-field kinematic measurements allows obtaining local information on the deformation and damage mechanisms at the microstructure scale. The present project proposes to tackle the intricate multi-physics dimension of the environment-assisted deformation/damage evaluation by simultaneously correlating the macroscopic/mesoscopic and sub-microstructure/sub-micrometer deformation and the changes in surface reactivity (oxide microcracking, oxide spallation, fast-growing oxides, breakaway oxidation, etc.) at high temperature in various atmosphere conditions. The main aspiration of this in-situ experimental characterization is to bring a novel understanding and a more physical prediction of the local and time-evolving mechanical behavior of graded materials at the microstructure scale related to environmental interactions.