Effect of Carbon and Nitrogen on the Hydrogen Embrittlement of 15Cr-15Mn-4Ni-Based Stable Austenitic Stainless Steels

Abstract

The effects of carbon and nitrogen on hydrogen embrittlement were investigated in stable austenitic stainless steels, Fe-15Cr-15Mn-4Ni-0.3Si with 0.3C or 0.3N (wt.%). The steels were electro-chemically charged under two different conditions and tensile tested at a slow strain rate. Hydrogen degraded the tensile properties in both alloys via different mechanisms. Hydrogen severely weakened the grain boundary strength of the nitrogen-added steel, resulting in early intergranular fracture. Carbon segregation increased the boundary strength, which reduced the extent of hydrogen embrittlement. Moreover, the degree of hydrogen-induced degradation was dependent on the depth of hydrogen penetration. Since the brittle fracture occurred only in the regions penetrated by hydrogen, the embrittlement ratio was not a good criterion to assess the susceptibility of the two steels to hydrogen embrittlement.