Resistivity-Microstructure Relationships in Nickel Base Superalloys Used in Gas Turbine Engines for Power Generation and as Interconnects in Solid Oxide Fuel Cells PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
This report summarizes the results accomplished during this 3-year with funds from this grant. The most important new contribution was the development of a microstructural model, based on analysis of the small angle scattering spectra that can relate the measured electrical resistivity to the precipitate population present in a nickel base superalloy in a quantitative way. A total of 24 research articles were published or were in press at the time the final report was written.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
This report summarizes the results accomplished during this 3-year with funds from this grant. The most important new contribution was the development of a microstructural model, based on analysis of the small angle scattering spectra that can relate the measured electrical resistivity to the precipitate population present in a nickel base superalloy in a quantitative way. A total of 24 research articles were published or were in press at the time the final report was written.
Author: Ricky Lee Whelchel Publisher: ISBN: Category : Electric resistance Languages : en Pages :
Book Description
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: Heather Joan Sharpe Publisher: ISBN: Category : Gas-turbine disks Languages : en Pages :
Book Description
Engineers constantly seek advancements in the performance of aircraft and power generation engines, including, lower costs and emissions, and improved fuel efficiency. Nickel-base superalloys are the material of choice for turbine discs, which experience some of the highest temperatures and stresses in the engine. Engine performance is proportional to operating temperatures. Consequently, the high-temperature capabilities of disc materials limit the performance of gas-turbine engines. Therefore, any improvements to engine performance necessitate improved alloy performance. In order to take advantage of improvements in high-temperature capabilities through tailoring of alloy microstructure, the overall objectives of this work were to establish relationships between alloy processing and microstructure, and between microstructure and mechanical properties. In addition, the project aimed to demonstrate the applicability of neural network modeling to the field of Ni-base disc alloy development and behavior. A full program of heat-treatment, microstructural quantification, mechanical testing, and neural network modeling was successfully applied to next generation Ni-base disc alloys. Mechanical testing included hot tensile, hot hardness, creep deformation, creep crack growth, and fatigue crack growth. From this work the mechanisms of processing-structure and structure-property relationships were studied. Further, testing results were used to demonstrate the applicability of machine-learning techniques to the development and optimization of this family of superalloys.
Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
The purpose of this project was to characterize the microstructural and microchemical effects of a process revision on HAYNES{reg{underscore}sign} 242{trademark}, a polycrystalline Ni-base superalloy used principally for high temperature applications, such as seal and containment rings in gas turbine engines. The process revision from the current one-step heat treating cycle to a two-step heat treatment would result in savings of energy and ultimately cost to the consumer. However, the proposed process revision could give rise to unforeseen microstructural modifications, such as a change in the size distribution of the ordered particles responsible for alloy strength or the formation of additional phases, which could affect alloy properties and hence performance. Advanced microcharacterization methods that allow images of the microstructure to be acquired at length scales from one micrometer down to the atomic level were used to reveal the effect of the process revision on alloy microstructure. Energy filtered imaging was used to characterize the size distribution and morphology of ordered precipitates and other phases, as well as the partitioning behavior of major elements (Ni, Mo, Cr) among these phases. The compositions of individual ordered particles, including fine-scale compositional variations at precipitate-matrix interfaces, and solute segregation behavior at grain boundaries were characterized at the atomic level by atom probe tomography. The atomic site distributions of selected elements in the ordered precipitates were characterized by atom-location by channeling-enhanced microanalysis (ALCHEMI). The results of these advanced microcharacterization methods were correlated with mechanical testing of similar alloys to address structure-property relationships.
Author: RA. MacKay Publisher: ISBN: Category : Creep Languages : en Pages : 20
Book Description
This paper discusses some of the microstructural features which influence the creep properties of directionally solidified and single-crystal nickel-base superalloys. Gamma prime precipitate size and morphology, ?-?' lattice mismatch, phase instability, alloy composition, and processing variations are among the factors considered. Recent experimental results are reviewed and related to the operative deformation mechanisms and to the corresponding mechanical properties. Special emphasis is placed on the creep behavior of single-crystal superalloys at high temperatures, where directional ?' coarsening is prominent, and at lower temperatures, where ?' coarsening rates are significantly reduced. It can be seen that very subtle changes in microstructural features can have profound effects on the subsequent properties of these materials.
Author: Hyo-jin Song Publisher: ISBN: Category : Languages : en Pages : 210
Book Description
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.
Author: Madeleine Durand-Charre Publisher: ISBN: 9781351409803 Category : Languages : en Pages :
Book Description
"Presents all the main aspects of the microstructure of nickel-base superalloys, and includes micrographs chosen from among a large range of commercial and academic alloys, from the as-cast product to in-situ components, worn from in-service use. Including more than 100 illustrations, the text explains all the transformation mechanisms involved in the origination (creation) of microstructures during solidification or heat treatments (crystallization paths, segregation, crystal orientation, precipitation, TCP, coarsening and rafting, etc.). It includes up-to-date information and data such as phase diagrams, crystallographic structures, and relationships with functional properties. Nearly 300 references provide a key to further investigation."--Provided by publisher.
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Author: Ricky Lee Whelchel
Author: Heather Joan Sharpe
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Author: RA. MacKay
Author: Hyo-jin Song
Author: J. M. OBLAK
Author: Madeleine Durand-Charre
Author: Randy Ray Bowman
Author: C. P. Sullivan