Hydrogen-induced cracking mechanism of precipitation strengthened austenitic stainless steel weldment

Precipitation strengthened austenitic stainless steels are widely used in hydrogen related applications. However, their applications may face hydrogen damage resulting in hydrogen-induced delayed failure. Results show that the weld is more sensitive to fracture and hydrogen-induced failure than the matrix. High density curved dislocations, abundant of large size precipitates and considerable γ′ precipitates coarsening are found in the weld. Large size precipitates are found to be major hydrogen traps and preferential microcrack nucleation sites. The γ′ precipitates coarsening make the weld more ductile than the matrix. With the decrease of the applied stress, hydrogen-induced cracking mechanism in the weld changes from brittle transgranular fracture to brittle intergranular fracture.