The effect of hydrogen, tritium and decay helium on the fracture toughness of a stainless steel superalloy

The effect of tritium and helium-3 on tensile properties, fracture toughness properties and fracture mechanisms was studied in a modified A-286 alloy, and compared to the effects of hydrogen. The yield strength and work hardening rate showed no sensitivity to helium-3 in the concentration range studied, but the tensile ductility decreased with increased helium concentration. Fracture toughness with tritium plus helium decreased below that obtained with hydrogen alone. Helium-3 caused a decrease in tensile ductility and fracture toughness because it precipitates on and induces failure at grain boundaries.