Effect of Hydrogen Content on Threshold Stress Intensity Factor in Carbon Steel in Hydrogen-Assisted Cracking Environments

Abstract Crack propagation of carbon steel (CS) caused by hydrogen in an overprotective buffer solution environment was investigated to determine the threshold stress intensity factor (KIH) for hydrogen assisted-cracking (HAC) using a wedge open-load (WOL) specimen. The K-value decreasing-type testing method was adopted as the experimental method. The possibility of crack propagation by cathodic protection (CP) in the soil environment was reviewed in relation to the equation proposed by Raju and Newman. The critical tensile strength for HAC was between 998 MPa and 1,396 MPa. The relationship between KIH and hydrogen content (C0) was obtained as KIH = 16.9 × (C0)−0.146. Crack propagation in soil would not occur because the evolved C0 was low. Transgranular fractures were observed in the area of high K values near the fatigue precrack. Most of the surface was covered with intergranular fractures. Transgranular quasi-cleavage fractures existed partially on the intergranular fracture surface, near the area of...