The effect of ordering on the hydrogen embrittlement susceptibility of Ni2Cr

Isothermal annealing at 500 °C for various lengths of time after rapid quenching from 900 °C results in different degrees of ordering in Ni2Cr. Tensile specimens of disordered and ordered Ni2Cr were subjected to hydrogen embrittling and nonembrittling environments before and during tensile testing. The hydrogen embrittlement susceptibility was determined by reduction-in-area losses (RA loss) after failure. The results of the tensile tests indicated that the disordered alloy and highly ordered alloy were the most susceptible to hydrogen embrittlement. The RA loss in each case was approximately 70 pct. The tests revealed a minimum susceptibility to hydrogen embrittlement between 40 and 50 pct order. The fracture surfaces of the specimens, as examined by scanning electron microscopy, showed that the extent of embrittlement is correlated with the amount of intergranular failure. The mechanisms for failure in Ni2Cr appear to depend upon the extent of aging in the alloy.