Temperature influence on hydrogen embrittlement of high-strength steel

High-strength steels (HSS) have growing applications in various industries due to their high strength and desirable strength-to-weight ratio. Using HSS in mobile and fixed structures improves the load bearing capacity, the safety, and the weight reduction. Despite these advantages, HSS are often susceptible to hydrogen embrittlement, which can occur during both manufacturing and service. Besides tensile stresses and hydrogen pressure, the temperature may affect the hydrogen diffusion behavior and, thus, the hydrogen embrittlement (HE) susceptibility of HSS in environments containing gaseous hydrogen. This study investigates the influence of temperature on hydrogen-assisted cracking of 55NiCrMoV7 HSS with the ultimate tensile strength of about 1.4 GPa exposed to gaseous hydrogen. To determine the threshold stress intensity factor of the HSS in hydrogen, KIH, modified wedge-opening-loaded specimens were subjected to constant displacement loading. The specimens were charged in hydrogen gas at 200 bar at room temperature, 100 °C, and 200 °C. The hydrogen absorption was measured using a thermal desorption analyzer. After ten days of charging, KIH was considerably lower than the fracture toughness determined in air. Moreover, KIH was found to depend on the temperature of the hydrogen gas.