Comparative evaluations on stress corrosion cracking mechanism of low alloy ultra-high strength steels in neutral 3.5 wt% NaCl solution

The stress corrosion cracking (SCC) mechanism of low alloy ultra-high strength steels 30CrMnSiNi2A and 40CrNi2Si2MoVA in neutral 3.5wt% NaCl solution is investigated by slow strain rate technique (SSRT), surface analysis technique and electrochemical measurements. At anodic polarization, 30CrMnSiNi2A shows excellent SCC resistance; on the contrary, 40CrNi2Si2MoVA displays much higher SCC susceptibility than 30CrMnSiNi2A. At cathodic polarization potential, the steels are both susceptible to hydrogen induced cracking (HIC). At OCP, SCC mechanism of 30CrMnSiNi2A is mainly under control of HIC; whereas, SCC process of 40CrNi2Si2MoVA at OCP is controlled by a mixed mode of HIC and anodic dissolution.