Visualization of trapped hydrogen along grain boundaries and its quantitative contribution to hydrogen-induced intergranular fracture in pure nickel

The phenomenon of hydrogen-trapping and its quantitative contribution to hydrogen-induced intergranular (IG) fracture were studied using a combination of thermal desorption analysis, secondary ion mass spectrometry and slow strain rate tensile tests. Hydrogen was trapped along grain boundaries (GBs) with a binding energy of ≈20 kJ/mol, accompanied by IG sulfur. The true fracture stress and fracture surface morphology were strongly dependent on the concentration of trapped hydrogen, leading to the conclusion that the hydrogen-induced IG fracture of pure Ni is controlled by the concentration of hydrogen trapped along GBs, and not by the concentration of lattice hydrogen.