Deformation and Damage Mechanisms of High Temperature Alloys: Directionally Solidified Ni Based Superalloys & Fe Based Superalloys
Sponsored by: TMS Structural Materials Division, TMS: High Temperature Alloys Committee
Program Organizers: Mark Hardy, Rolls-Royce Plc; Jonathan Cormier, ENSMA - Institut Pprime - UPR CNRS 3346; Jeremy Rame, Naarea; Akane Suzuki, GE Aerospace Research; Jean-Charles Stinville, University of California, Santa Barbara; Paraskevas Kontis, Norwegian University of Science and Technology; Andrew Wessman, University of Arizona

Wednesday 4:00 PM
March 2, 2022
Room: 304B
Location: Anaheim Convention Center

Session Chair: Jeremy Rame, Safran Aircraft Engines; Akane Suzuki, GE Research


4:00 PM  Invited
Very High Cycle Fatigue Properties of CoNi- and Ni-based Single-crystal Superalloys: Alice Cervellon1; Tresa Pollock2; Chris Torbet2; 1Institut Pprime; 2University of California Santa Barbara
    Co-base superalloys have been studied over the past decade, since γ/γ' microstructures with high volume fractions of the L12 phase were demonstrated in ternary Co-Al-W alloys. More complex compositions based on this system are promising for applications in turbine engines, especially for CoNi systems that present a higher oxidation resistance. In these alloys, the high portion of Co results in lower stacking fault energies, which affect the deformation mechanisms. The influence of stacking fault energy on creep deformation has been studied, but its influence on other properties such as very high cycle fatigue is not understood. This work aims at studying the VHCF properties of a single-crystal CoNi-based superalloy at 750°C and 950°C. The crack initiation stage and the fatigue life have been characterized and compared with Ni-base superalloys. Finally, characterizations performed on Ni-based SX superalloys will be presented to better understand the crack initiation stage in the VHC regime.

4:30 PM  
On the Influence of γ’-particle Size on the Yield Stress Anomaly in Ni-base Single Crystal Superalloys: Marc Sirrenberg1; David Bürger1; Alireza Parsa1; Gunther Eggeler1; 1Ruhr-University Bochum
    The yield stress of Ni-base superalloys (SX) can increase with temperature, a phenomenon referred to as yield stress anomaly (YSA). Attempts have been made to study the influence of γ’-particle volume fractions on YSA. In contrast, little is known about the effect of γ’-particle size. In the present work we use a reference material of type CMSX4 which was directionally solidified in a Bridgman process and then exposed to a standard multiple-step heat treatment. We characterize the γ’-particle size distribution of this reference state. We then apply specific heat treatments to produce two additional material states, which have the same γ'-volume fraction but exhibit larger and smaller γ'-particles. The intensity of YSA at temperatures between 750 and 950°C increases with increasing γ'-particle sizes at constant γ'-volume fraction. We discuss the findings in the light of results obtained from quantitative analytical scanning and transmission electron microscopy.

4:50 PM  
Mechanistic Modeling of Thermal Creep Response of 347H Stainless Steel: Effect of Microstructure and Chemistry: Arul Kumar Mariyappan1; Ricardo Lebensohn1; Laurent Capolungo1; 1Los Alamos National Laboratory
    Austenitic stainless steels are widely used in high-temperature applications like nuclear and fossil energy industries. Developing a numerical framework to capture the creep and strain hardening behavior of steels is important to enhance its applicability. In this work, a mechanistic constitutive model within a full-field elasto-visco-plastic Fast Fourier Transform (EVPFFT) framework is developed to capture the effect of stress, temperature, microstructure and chemistry on material responses. Thermally-activated dislocation glide and climb, and vacancy diffusional creep mechanisms are considered. Using this framework, uniaxial stress-strain and thermal creep responses of 347H stainless steel for wide range of temperature is predicted and validated against the experimental measurements. Ashby-Weertman deformation mechanisms maps are developed for different initial microstructures and chemistry. The relative roles of the different deformation mechanisms (dislocation glide, climb and diffusional creep) on the predicted creep responses are discussed.