Characterization of Hydrogen Induced Contact Fracture in High Strength Steel

Abstract

This study investigated the hydrogen embrittlement (HE) cracking behavior produced by local contact loading of highstrength steel. When a spherical impression was applied to a hydrogenabsorbed highstrength steel, HE induces contact fracture, where radial cracks are initiated and propagated from the indentation impression. The length of the radial crack was found to be dependent on the hydrogen content in the steel as well as the applied contact force. A combined experimental/computational investigation was conducted in order to clarify the mechanism of hydrogeninduced contact fracture. In the computation, crack propagation was simulated using a cohesive zone model (CZM) in finite element method (FEM), in order to elucidate stress criterion of the present HE crack. It was found that the normal tensile stress was developed around impression, and it initiated and propagated the HE crack. It was also revealed that the hydrogen content enhanced contact fracture damage, especially the resistance of crack propagation (i.e., threshold stress intensity factor, Kth). The findings may be useful for countermeasure of contact fracture coupled with hydrogen in highstrength steel. Such phenomenon is potentially experienced in various contact components in hydrogen environment.