Synergistic Effect of Hydrogen and Sulfur on Ductility Loss in Pure Nickel Accompanied by Hydrogen-Induced Intergranular Fracture

Abstract

Synergistic effect of hydrogen and sulfur on intergranular (IG) fracture and resultant ductility loss in pure nickel was quantitatively evaluated by means of Auger electron spectroscopy, thermal desorption analysis and slow strain rate tensile test. Both hydrogen and sulfur enhanced IG fracture, leading to the degradation of ductility. Increased sulfur concentration at grain boundaries (GBs) resulted in an appearance of second peak around 400°C in TDA profiles, indicating that the segregated GB sulfur trapped hydrogen. However, its trapped hydrogen hardly enhanced the hydrogen-induced ductility loss. Instead, hydrogen directly trapped at GBs was responsible for IG fracture and degradation of ductility. These results indicate hydrogen and sulfur independently induced the IG fracture and resultant ductility loss and therefore, the synergistic effect is negligible.