Effect of hydrogen charging on the interphase microstrains and stacking fault energies of γ'-hardened single crystal superalloys

The use of hydrogen as a zero-carbon energy source presents challenges due to its interaction with structural materials, particularly in gas turbine engines. This study examines the effects of hydrogen charging on interphase microstrains and stacking fault energy (SFE), which influence the deformation behavior of γ′-hardened single crystal (SX) superalloys. These superalloys, with a face-centered cubic (FCC) γ matrix and embedded γ′ precipitates, are critical for high-temperature turbine applications but have been understudied regarding hydrogen’s effects beyond embrittlement. Elastic microstrains arise from the lattice misfit between the two phases, depending on the magnitude and difference in their lattice parameters.
In this research, three SX superalloys are studied: Ni-based CMSX-4 (small negative lattice misfit), LDSX6-A (large negative lattice misfit), and Co-based VF60 (positive lattice misfit). In situ neutron diffraction is employed to measure lattice parameters, interphase microstrains, and SFE during compression tests, both before and after hydrogen charging at 1000 bar and 300°C. Previous studies suggest hydrogen uptake lowers SFE, and this research aims to compare the SFE of hydrogen-free and hydrogen-charged samples to further understand hydrogen's influence on SFE. These findings contribute to the understanding of hydrogen’s effects on high-temperature alloys, with implications for their future use in hydrogen-powered systems.