Effect of Hydrogen on Crack Initiation and Growth in 18Mn-4Cr Steel

Hydrogen-assisted cracking in generator rotor end rings is a major concern of the utility industry. To assess the susceptibility of an austenitic 18Mn-4Cr end ring steel to a hydrogen environment, an experimental program was carried out to determine crack initiation and fatigue crack growth properties in hydrogen gas and air. In this program, a peak read detection circuit was designed to determine accurately crack initiation and early crack growth. Test results show that a hydrogen environment does not significantly influence the crack growth rate; however, it reduces the crack initiation life at a low notch root stress range.