EFFECT OF HYDROGEN ON CRACK PROPAGATION BEHAVIOR AND MICROSTRUCTURES AROUND CRACKS IN AUSTENITIC STAINLESS STEELS.

Abstract

Yield strength and flow stress at 2% strain are not dependent on hydrogen content, whereas the fracture strain and the total energy spent in the tensile test decrease as the hydrogen content increases. According to notch tensile tests, the force for crack initiation does not change with increase in hydrogen content, but the plastic strain induced and the work required for fracture decrease with increasing hydrogen. Hydrogen suppresses the strain-induced transformation of gamma to alpha prime martensite, while it promotes the formation of epsilon martensite by lowering stacking fault energy.