Effect of Alloying Elements on γ→ε Phase Transformation in Hydrogen-Charged Austenitic Steels and on Hydrogen Embrittlement

The effect of alloying elements (Cr, Mn, Ni, Cu, Al, Si, Mo) on the fraction of the hydrogen-induced epsilon-martensite is studied. As shown, Cr, Mn, Si promote the hydrogen-induced gamma ->epsilon-transformation, whereas Ni, Cu, Al suppress it. The fraction of the hydrogen-induced e-martensite decreases or increases in accordance with the corresponding change in stacking fault energy caused by alloying. A correlation is revealed between the effect of alloying elements on the hydrogen-conditioned gamma ->epsilon-transformation and hydrogen embrittlement of austenitic steels: the higher epsilon fraction the more resistant is the austenitic steel against hydrogen embrittlement. This result is at variance with the generally accepted opinion about the epsilon-martensite as a cause for hydrogen-induced brittleness.