The Influence of Deformation Temperature on the Initiation of Hydrogen-Induced Intergranular Cracking in Nickel

The influence of deformation temperature on the initiation of hydrogen-induced intergranular cracking was evaluated through testing at ambient temperature and 77 K, corresponding to conditions where hydrogen-deformation interactions are possible and effectively precluded, respectively. Uniaxial tensile testing of hydrogen-charged specimens, coupled with detailed microscopy of sectioned specimens, facilitated the assessment of the total number and cumulative length of intergranular microcracks as a function of true strain. Hydrogen-induced microcracks were found to initiate at true strains of 0.12 and 0.2 when tested at ambient temperature and 77 K, respectively. These results suggest that hydrogen segregated to the grain boundary prior to deformation dominates the initiation of hydrogen-induced intergranular microcracks, while hydrogen-deformation interactions provide an important, but ultimately secondary, contribution.