HYDROGEN EMBRITTLEMENT OF LOW-CARBON 13%Cr6%NiMo MARTENSITIC STAINLESS STEEL

ABSTRACT The paper reports on a study of the mechanical metallurgy characteristics of hydrogen embrittlement, defined by the K ISII threshold levels, in a low-carbon type 13%©6%NiMo steel after various alternative heat treatments. These included single-stage tempering at temperatures ranging from 200 to 580°C, two-stage tempering by six hours each at 670 and 580°C, both followed by air cooling, and this latter treatment supplemented by further annealing at 550°C. The findings demonstrate the favourable effect of an increased austenite content in the matrix, which acts as a hydrogen trap and thereby partly suppresses the harmful effects of phosphorus segregation at prior austenite grain boundaries.