Materials for High Temperature Applications: Next Generation Superalloys and Beyond: Superalloys: Processing
Sponsored by: TMS Structural Materials Division, TMS: Refractory Metals Committee
Program Organizers: Govindarajan Muralidharan, Oak Ridge National Laboratory; Martin Heilmaier, KIT Karlsruhe; Benjamin Adam, Oregon State University; Mario Bochiechio, Pratt & Whitney; Katerina Christofidou, University of Sheffield; Eric Lass, University of Tennessee-Knoxville; Jeremy Rame, Naarea; Sallot Pierre, Safran; Akane Suzuki, GE Aerospace Research; Michael Titus, Purdue University
Wednesday 8:30 AM
March 17, 2021
Room: RM 8
Location: TMS2021 Virtual
Session Chair: Akane Suzuki, GE Aerospace Research; Michael Titus, Purdue University
8:30 AM Keynote
Considerations for Manufacturability and Repairability of Next Generation High Temperature Alloys: Robert Proctor1; 1Rolls-Royce Corporation
The continued need for higher performance and reduced environmental footprint is reigniting the demand for the next generation of high temperature metal alloys and coating systems. Material production methods, such as additive layer manufacturing, are emerging and will enable higher performance designs for aerospace gas turbines. The challenge for academia and industry is to work together to ensure that these next generation materials are developed with an eye towards manufacturability and repairability. Not only should the focus be on higher performance, but the overall environmental footprint of the system. This presentation will show how new aerospace propulsion systems can deliver higher performance while minimizing environmental impact by taking advantage of new high temperature material systems coupled with advanced manufacturing methods and approaches to implementation of material processes.
9:10 AM
Observation of Multiply Coherent Grains in Ni-Based Superalloy LSHR: Cameron Hale1; Brady Dowdell2; Victoria Miller1; 1University of Florida; 2North Carolina State University
The primary gamma prime phase plays a critical role in controlling grain size evolution during thermomechanical processing of polycrystalline Ni superalloy. Recently, multiply coherent grains (MCG), or gamma grains containing multiple coherent primary gamma prime particles have been observed in the Ni-base superalloy LSHR over a range of thermomechanical processing conditions. These MCGs would provide stronger Zener pinning pressure than a conventional incoherent array of primary particles, so understanding their formation is important. MCGs in this paper are quantitatively characterized using energy dispersive spectroscopy (EDS) paired with electron backscatter diffraction (EBSD) techniques. Potential explanations for their formation and implications on the microstructural effects are discussed.
9:30 AM
Feasibility of Near-net-shape HIP Fabrication and PM/Wrought Weld in Alloy IN740H for AUSC Components: Shenyan Huang1; Victor Samarov2; Jack deBarbadillo3; Timothy Hanlon1; Beth Lewis4; Ronnie Gollihue3; John Shingledecker5; Jason Mortzheim1; 1GE Research; 2Synertech PM Inc.; 3Special Metals; 4Wyman-Gordon; 5Electric Power Research Institute
To reduce manufacturing cost and CAPEX of advanced ultra-super critical (AUSC) steam components, powder metallurgy (PM) based near-net-shape (NNS) HIP fabrication was investigated as an alternative manufacturing modality. Feasibility of NNS HIP for this application was demonstrated in a ~65kg pipe elbow using gas atomized powder of alloy IN740H. A finite element HIP simulation was performed to predict the non-uniform shrinkage during HIP and to design the HIP capsule of the pipe elbow. Measured physical and mechanical properties of partially and fully densified IN740H powder were used for model calibration. The HIP cycle was tuned to optimize grain size and achieve balanced properties. Creep performance of PM HIP’ed IN740H was evaluated at 700~800°C, up to 500 hours. PM HIP to wrought IN740H welding procedures were also developed to obtain reasonable microstructure and cross-weld mechanical properties.
9:50 AM Invited
Understanding the Effects of Alloy Chemistry and Microstructure on the Stress Relaxation Behavior of High Strength Ni-base Superalloys: Sammy Tin1; 1Illinois Institute of Technology
Recent advances in processing and a better understanding of composition – property relationships have led to the development of innovative high strength, creep resistant Ni-based superalloys used for disk rotor components. Many of these alloys utilize a higher volume fraction of γ′ precipitates along with a more potent level of solid solution strengthening to achieve these improved properties. Although the strength and temperature capability of powder processed Ni-base superalloys have been significantly improved, these materials are also known to be more difficult to manufacture and are more sensitive to stress concentration features, such as notches and other defects. Controlling the formation of residual stresses during processing and understanding the characteristic stress relaxation behavior of the material has become increasingly important for the design and implementation of new alloys. In this investigation, the results of stress relaxation testing from various high strength powder processed Ni-base superalloys with varying initial microstructures will be presented. The role of chemistry and microstructure on the characteristic stress relaxation response of the alloy will be discussed.
10:20 AM
Synchrotron X-Ray Scattering Characterization of Strengthening Precipitates in a Model Ni-based Alloy: Matthew Frith1; John Chiles2; Jonathan Poplawsky2; Jan Ilavsky1; Govindarajan Muralidharan2; 1Argonne National Laboratory; 2Oak Ridge National Laboratory
High performance Ni-based alloys are required for use in exhaust valve applications in the next generation, high efficiency automotive engines. Simultaneous small angle x-ray scattering (USAXS/SAXS) and diffraction (WAXS) were applied for the ex situ and in situ characterization of the γ’ precipitates in a model Ni-based alloy. Understanding microstructure of the γ’ precipitates is critical to achieving the desirable performance characteristics of these alloys in this application. Multiple modeling approaches were applied to the small-angle scattering data; for general characterization the Unified fit model, and a particulate model of particle size distribution with various shape form factors combined with structure factor for advanced analysis. Effect of models used on particle sizes obtained will be elucidated. In situ measurements were used to characterize precipitate coarsening behavior with respect to time and temperature.
10:40 AM
On the Early Stages of Gamma’ Evolution in a Model Ni-based Alloy: Govindarajan Muralidharan1; Shivakant Shukla1; John Chiles1; Dean Pierce1; Larry Allard1; Balasubramaniam Radhakrishnan1; Jonathan Poplawsky1; 1Oak Ridge National Laboratory
High performance Ni-based alloys are required for use in exhaust valve applications in the next generation, high efficiency automotive engines. These alloys are expected to be as low as possible in cost while being able to perform at temperatures up to 950°C in an exhaust gas environment. This talk will present results from our work on the early stages of gamma’ evolution in a model Ni-Fe-Cr alloy. The work will highlight the use of transmission electron microscopy, atom probe tomography and phase field modeling in understanding microstructural evolution in this model Ni-Fe-Cr alloy. *Research sponsored by the U.S.DOE, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. Atom probe tomography was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User facility.