Influences of (Al, Ca, Si, Nb, Mn)-oxy-sulfide inclusions on corrosion degradation for newly designed 17–4 martensitic PH steel in simulated geothermal environments

Influences of (Al, Ca, Si, Nb , Mn)-oxy-sulfide inclusions on hydrogen trapping and stress corrosion cracking in a newly designed 17–4 martensitic PH steel were carried out under simulated geothermal environments based on experiments and calculations. The results indicate that CaS and MnS in inclusions are not only prone to preferential dissolution, but also more likely to become hydrogen trapping sites at the interface with matrix than other components. The number of pits rapidly increase before the sample fracture at 159.25 h, while cracks around external pits and internal gourd-like cavities are probably attributed to the uneven expansion of inclusion-triggered pits.