Abstract
Susceptibility to embrittlement in hydrogen gas was investigated for three types of stainless steel alloys having different microstructures. Both slow strain rate notched tension tests and constant load crack propagation tests were used to evaluate susceptibility at 0 to 200°C in hydrogen gas at 108 kPa (1 psig). The alloys were austenitic, ferritic, or austenite/ferrite mixtures produced by different thermomechanical treatments. The onset of embrittlement and crack propagation rates could be correlated with the microstructure of the alloys. Of particular importance to the understanding of the results are the marked hydrogen transport and solubility differences between the austenite and ferrite phases. The stress-induced transformation of austenite to body-centered cubic (bcc) martensite has particular relevance in rationalizing the behavior of various austenitic stainless steel alloys.