2012 Volume 6 Issue 4 Pages 265-277
The effect of hydrogen exposure on high strength steel, SCM435, based on a sharp notched specimen was investigated. Tensile tests were carried out in hydrogen gas and helium gas environments. In the hydrogen gas environment, specimens that were not exposed to hydrogen gas and specimens that were exposed to hydrogen gas for 48 h were used. As the result of the tensile tests with specimens of various notch depths, the tensile strengths of the hydrogen-gas-exposed specimens were higher than that of the non-exposed specimens. The tensile strength increases with the exposure time in hydrogen gas until hydrogen homogeneously diffuses in the entire specimen for the notched specimens of t =1.0 mm. The fracture surfaces of the specimens in hydrogen gas showed an intergranular fracture near the notch root while the specimens in helium gas showed a fracture mode of microvoid coalescence. The crack initiation stress of the non-exposed specimen was lower than that of the 48h-hydrogen-exposed specimen.
