Tensile properties of an electrolytically hydrogen charged duplex stainless steel affected by strain rate

Abstract

To provide a reliable relationship between hydrogen embrittlement (HE) and the behavior of hydrogen in duplex stainless steels (DSSs), we evaluated the tensile behavior of electrolytically charged DSS (JIS SUS329J4L) specimens at various strain rates. Immediately after hydrogen charging, tensile tests were performed at strain rates ranging from 1.38×10?7 to 1.38×10?3s?1. Fracture surface was evaluated by scanning electron microscope (SEM) and the concentration of hydrogen was measured by thermal desorption spectroscopy (TDS). It was confirmed that elongation to failure was decreased with increasing charging time for testing at 1.38×10?6s?1, while ultimate tensile strength was not affected markedly by hydrogen charging. The extent of HE took a maximum at a strain rate of 1.38×10?4s?1. Tensile test results and results of fracture surface evaluation by SEM were consistent to each other: the fraction of smooth area (area without dimples) with respect to the whole fracture area also took a maximum at the strain rate of 1.38×10?4s?1. These results were correlated to the balance between hydrogen diffusion and hydrogen desorption during the test. By TDS, the concentration of the diffusive hydrogen was confirmed to increase with increasing charging time. Hence, the extent of HE was strongly dependent on the concentration of the diffusive hydrogen.