Effects of cold rolling on the mechanical behavior of 904L superaustenitic stainless steel in hydrogen environments

The effect of cold rolling on the tensile and fracture toughness properties of an austenitic AISI 904L steel in the presence of hydrogen is studied in this research work. An annealed 904L plate was submitted to thickness reductions of 10, 20 and 30 % by cold rolling. The hydrogen trapping and diffusion kinetics, and subsequently the mechanical performance of these three grades were studied by means of tensile tests and fracture toughness tests performed in air and after hydrogen pre-charging. The effect of cold rolling on hydrogen trapping was also measured. Before hydrogen precharging, cold rolling produces a dramatic increase in yield strength and a decrease in fracture toughness. Nevertheless, hydrogen entrance barely modifies the fracture toughness of all these grades nor the operative failure micromechanism, which was always fully ductile: coalescence of microvoids after plastic deformation. The fracture toughness of the three cold-rolled austenitic 904L grades in hydrogen was shown to be greater than that of ferritic steels used nowadays in applications under high hydrogen pressure such as pressure vessels and pipelines. This is true even in the case of the two grades with higher yield strength (700–800 MPa), corresponding to those produced after 20 and 30 % thickness reductions.