Effects of hydrogen on fatigue-crack propagation in steels

摘要: Abstract: This chapter presents a review of several important phenomena associated with the influence hydrogen on process growth fatigue cracks in steels. In first part chapter, we describe internal for higher-strength low alloy (Cr–Mo) and austenitic stainless steel; second part, corresponding description external (hydrogen gas) fatigue-crack propagation classes lower-strength pressure vessel piping steels is given. We show that critical mechanistic can be enhanced by presence hydrogen, including localization slip bands fatigue, situ transformation to strain-induced martensite (Types 304, 316 316 L), effect frequency rates. The nature fracture surface, specifically morphology striations, consequent role crack closure, also influenced hydrogen. With regard (gaseous hydrogen), based measurements over wide range rates from 10− 11 10− 5 m/cycle, crack-propagation significantly higher dehumidified gaseous as compared moist air two distinct regimes growth, namely, at intermediate typically above ~ 10− 8 m/cycle threshold region below ~ 10− 9 m/cycle approaching lattice dimensions/cycle. lower strength steels, both effects are seen maximum stress intensities Kmax far intensity hydrogen-assisted cracking under sustained (non-cyclic) loading. Comparing acceleration due interpreted function concentration tip, any variation active mechanisms closure.