INFLUENCE OF INTERNAL HYDROGEN ON THE HYDROGEN EMBRITTLEMENT OF AUSTENITIC STAINLESS STEEL

The HE (hydrogen embrittlement) behavior of two kinds of austenitic stee Cr21Ni6Mn9 and 1Cr18Ni9Ti is reprted in this paper. The factors (temperc-ture/strain rate/stress concentration coefficient and purity of hydrogen) are restricted to the severe conditions under which HE is easy to occur. The concentmtion of in-ternal hydrogen in samples is changed by varying the time during which samples are placed in 24 MPa hydrogen at 473 K Then the tensile properties of the samples are tested. The results indicate that the degree of the hydrogen-induced plastic loss (L)of Cr21Ni6Mn9 is different with the internal hydrogen(CH). Howeven even when CH is as high as 70 PPm L is 15% and the fracture may be explained as a larpe amount of internal hydrogen hinders the cross-slip of dislocations when the steel is deforming.For the metastable steel 1Cr18Ni9Ti the hydrogen-induced plastic loss is severer than that of Cr21Ni6Mn9. When CH is 40 PPm its L is as high as 42%. The mechanism may be explained as a larpe amount of hyderpen decreases the stacking fault enerpy and brittle ε-phase is produed in the high CH areas.