The effect of hydrogen on the fracture of a commercial duplex stainless steel

The effect of hydrogen on the fracture behaviour of a duplex stainless steel has been studied by slow tensile straining of specimens thermally-charged with hydrogen in air and uncharged specimens in hydrogen gas. A strain-rate-dependent loss in ductility was discovered in both types of test but significant differences were also observed. Crack initiation was associated with inclusions in the charged material but with the ferrite at the surface when strained in hydrogen. Where the hydrogen supply was limited, ε-martensite was found to play a significant role in the embrittlement. Recovery of ductility on annealing charged specimens at temperatures up to 400°C was found to be related to the release of hydrogen from inclusions and diffusion through the ferrite at lower temperatures but became dependent upon diffusion through the austenite at higher temperatures.