Stress corrosion cracking behavior of 16Mn steel and heat-affected zone in alkaline sulfide with different Ph value

The behavior and mechanism of stress corrosion cracking (SCC) of 16Mn steel and its heat-affected zone (HAZ) in alkaline sulfide and Cl^- solution medium with different pH value was investigated by U-bent specimen immersing test and electrochemical technology. Results show that the original microstructure, the coarse grain structure (air cooling structure) and the hardening microstructure (quenching structure) exhibit a similar passivation state in alkaline sulfide solution with pH=11.8, passive current density gradually decreases; As pH value decreases, anodic process of original structure and coarse grain structure gradually change from the passivation state to the activation state. The SCC susceptibility of the hardening structure, coarse grain structure and original structure of heat-affected zone (HAZ) in alkaline sulfide environment gradually decreases, the hardening structure exhibits obvious SCC feature. With the decrease of pH, SCC cracks tend to change from intergranular cracks to transgranular and intergranular combined cracks and the width of the cracks increases.