Advanced Characterization of High-temperature Alloys: Phase Evolution during Manufacturing and Service-induced Deformation: Deformation Assisted Microstructural Control of High Temperature Alloys During Manufacturing Processes
Sponsored by: TMS Structural Materials Division, TMS: High Temperature Alloys Committee
Program Organizers: Katerina Christofidou, University of Sheffield; Benjamin Adam, Oregon State University; Stoichko Antonov, Max-Planck Institut für Eisenforschung GmbH; James Coakley, Chromalloy; Martin Detrois, National Energy Technology Laboratory; Paraskevas Kontis, Norwegian University of Science and Technology; Stella Pedrazzini, Imperial College London; Sophie Primig, University of New South Wales
Monday 8:30 AM
March 20, 2023
Room: 29D
Location: SDCC
Session Chair: Katerina Christofidou, The University of Sheffield; Sophie Primig, University of New South Wales
8:30 AM Introductory Comments
8:35 AM Invited
A New Paradigm for Wrought Superalloys with Superior Fatigue Strength: Marie Charpagne1; JC Stinville2; 1University of Illinois at Urbana-Champaign; 2University of Illinois
With unmatched mechanical performance at high temperature, wrought Nickel-base superalloys have been used in the energy and aerospace industries for decades. While broad alloy design and microstructure optimization efforts have been made towards tailoring their strength, less attention has been paid to improving their fatigue strength. Recent advancements in digital image correlation have enabled to capture the micro-mechanisms at the origin of fatigue crack initiation, revealing the central role of slip localization, a phenomenon tightly linked to the materials microstructure. Here, we explore a new microstructure design strategy aiming at minimizing the intensity of slip localization. Building-up on concurrent knowledge on microstructure evolution during forming processes (recrystallization, grain growth and phase transformations), we will present several pathways to increase the fatigue performance of these alloys, through the examples of Waspaloy and Rene 65. The efficacy of these strategies will be discussed based on statistical measurements at the micro- and macro-scale.
9:05 AM Invited
Grain Boundary Microstructure Optimization in Ni-Co-based Wrought Superalloys: Akane Suzuki1; Steve Buresh1; Richard DiDomizio1; Scott Oppenheimer1; Ian Spinelli1; 1GE Research
Ni-Co-based gamma + gamma-prime superalloy compositions containing high W were explored for designing a wrought superalloy with a combination of superior high temperature strength and environmental resistance at temperatures above 927C (1700F). Effects of alloying elements on ductility, creep life, hold-time low cycle fatigue life, fatigue crack growth behavior, oxidation resistance and manufacturability were investigated for achieving a balance of properties. Detailed characterization of phases and morphology of precipitates was performed, and it was found that a formation of Co2W Laves precipitates along grain boundaries plays an important role in improving ductility in the intermediate temperature range and fatigue crack growth behavior.
9:35 AM
Accelerating Alloy Development for Additive Manufacturing: Elisabeth Kammermeier1; Carolin Körner1; Christopher Zenk1; 1FAU Erlangen-Nuernberg, WTM
Powder of newly developed compositions for additive manufacturing (AM) is usually unavailable. Two approaches will be presented to (i) mimic selected-electron-melted (SEBM) microstructure formation and evaluate the crack susceptibility, and (ii) produce samples with a suitable microstructure for mechanical testing without the need for powder. For this proof-of-concept study on MAR-M247 derivates, a SEBM-re-melting procedure was developed, in which the energy density was successively decreased to mimic the layer-by-layer structure of AM. This allows characterization of the SEBM-processibility but limits mechanical testing. Therefore, a recrystallization study after hot and cold deformation of arc-melted material has been performed to obtain grain sizes more comparable to typical SEBM-processed microstructures. Especially the samples that underwent cold deformation show a promising, homogenous microstructure due to the prevention of dynamic recrystallization.
9:55 AM
Influence of Local Thermal History during Laser Powder Bed Fusion Additive Manufacturing on Solidified Microstructure and Phase Transformations during Subsequent Heat Treatment: Andrew Wessman1; Yi Zhang1; 1University of Arizona
Changes in processing parameters and part geometry in laser powder bed fusion additive manufacturing can influence the local thermal history of materials during the build process. These variations in factors such as cooling rate, solidification velocity and peak temperature can result in changes in the as-solidified cellular precipitate and/or grain structure in superalloys processed in this way. This presentation will describe the effect of changing thermal history on the microstructure of as-built superalloys IN718 and Haynes 282 and the impact of these variations on subsequent microstructural evolutions during solution heat treatment and aging cycles. Thermal history will be obtained through in-situ thermal tomography of the AM process, which will also be used to compare observed results to those obtained through Scheil models of the solidification process and CALPHAD and precipitation models of the expected microstructures.
10:15 AM Break
10:35 AM Invited
Segregation-assisted Yield Strength Anomalies in Superalloys: Steffen Neumeier1; Andreas Bezold1; Mathias Goeken1; 1Friedrich-Alexander-Universität Erlangen-Nürnberg
In the past decade, the significance of segregation of alloying elements to defects during high temperature deformation of superalloys strengthened by L12 precipitates became evident. Previous investigations revealed that segregation processes facilitate shearing of the ordered phase by lowering defect energies causing softening. Here we show that segregation-assisted processes can also induce an anomalous increase in the yield strength of Co- and CoNi-base superalloys. By facilitating the dissociation of dislocations at the matrix/precipitate interfaces in combination with an atomic-scale reordering process of the resulting planar defects, these processes cause an impediment of low temperature shearing mechanisms. This leads to a transition of the operating deformation mechanism and the observed strengthening effect. Our results unravel the elementary mechanisms why the transition to stacking fault shearing does not necessarily cause softening. Furthermore, the significance of segregation on the operating deformation mechanisms is revealed which can guide alloy design of novel superalloys.
11:05 AM
Effect of Machining Processes on the Perceived Mechanical Properties of Tantalum Refractory Alloys: Christopher Finfrock1; Zahra Ghanbari1; Rachel White1; Charles Robino1; Christina Profazi1; Jay Carroll1; Stephen Spiak1; Bonnie Antoun1; 1Sandia National Laboratories
Tantalum alloys are used extensively in high-temperature structural components. In such high-temperature operating conditions, it is understood that Ta-W alloys can be susceptible to oxidation-induced embrittlement, which can cause a nil-ductility condition despite their notionally high-toughness. The response of these alloys to machining is unclear, because machining processes may influence the composition and structure of the surface. For instance, it is hypothesized that wire EDM could introduce oxygen or hydrogen, while conventional milling could increase the local dislocation density. In this study, surface and bulk micro-mechanical tests are complimented by a suite of characterization tools to explore the effect of machining processes on the structure and mechanical performance of Ta-10W and Ta-8W-2Hf (T-111) alloys. The results presented here have important implications for accurately measuring the material properties used as inputs for mechanical models of high-temperature structural components.Sandia-National-Laboratories-is-a-multimission-laboratory-managed-and-operated-by-National-Technology-and-Engineering-Solutions-of-Sandia,-LLC.,-a-wholly-owned-subsidiary-of-Honeywell-International,-Inc.,-for-the-U.S.-Department-of Energy’s-National-Nuclear-Security-Administration-under-contract-DE-NA0003525.
11:25 AM
Effects of Heat-Treatment on the High-Temperature Wear Behaviors of Additively Manufactured Inconel 718: Zhengyu Zhang1; Wenjun Cai1; 1Virginia Polytechnic Institute and State University
Various high temperature applications such as control rods, thrust bearings, shafts, and fasteners in nuclear power plants, compressors, propulsion systems and aero engines demands structural materials with excellent wear resistance at high temperatures. In this study, the microstructure, mechanical, and tribological characteristics of Inconel 718 produced via laser powder bed fusion were studied experimentally. In a ball-on-plate mode, the hot tribological behavior of the alloys fabricated with and without heat treatment was studied from 600 °C to 900 °C. The worn surfaces and cross-sections were analyzed with the aid of SEM/EDS, XRD and XPS analysis. The differences in wear rate and coefficient of friction of Inconel 718 with and without heat treatment were observed. In the end, the high temperature wear behavior of these alloys is discussed based on both experimental and CALPHAD calculation results to elucidate the different roles of individual alloying component on surface oxidation and friction.
11:45 AM
Surface Integrity and Microstructural Characterization of Additively Manufactured Inconel 625 subjected to Shot Peening and Laser Peening: Manisha Tripathy1; LLoyd Hackel2; Keivan Davami3; Ali Beheshti1; 1George Mason University; 2Curtiss Wright Surface Technologies; 3The University of Alabama
Surface enhancement processes like laser peening (LP), and shot peening (SP) are being extensively used in harsh environment applications for decades now to improve the mechanical and surface behavior of parts. With the rapid growth of the metal additive manufacturing industry, it becomes necessary to rigorously study the additively manufactured components trying to achieve comparable or even superior properties with reference to their conventional counterparts. This study showcases a detailed microstructural and surface property comparison between additively manufactured(AM) and wrought(WR) Inconel 625 with LP and SP processes. Surface morphology and mechanical properties, as well as advanced characterization techniques like XRD, EBSD, PED, and TEM, were employed to collate the deformation mechanisms and defect evolution in the microstructure due to the peening processes.