Effects of Hydrogen Pressure on Crack Growth Rates in an Iron Based Superalloy

Austenitic superalloys are often used in hydrogen and hydrogen-producing environments due to their good resistance to hydrogen effects. There have been several studies on how hydrogen affects thresholds in bcc iron and steels and fcc superalloys, but very few on crack growth rates. In this paper, crack growth models will be used to show that the differences in crack growth susceptibility and fracture modes from external hydrogen are due to the combined effects of microstructure, hydrogen diffusivity, and time-dependent stress enhancement on crack tip hydrogen concentrations.