Study on Stress Corrosion Susceptibility of High Manganese Austenitic Cryogenic Steel HM400 in Liquid Ammonia Medium

For studying the stress corrosion susceptibility of high manganese austenitic cryogenic steel HM400 in liquid ammonia medium, the slow strain rate test (SSRT) was used to investigate the stress corrosion susceptibility of high manganese austenitic cryogenic steel HM400 in four media: pure liquid ammonia (NH3), air+liquid ammonia (NH3+Air), 0.1 mg/L H2O+pure liquid ammonia (NH3+0.1 mg/L H2O) and air (Air) at room temperature. The fracture micro morphology, crack morphology, change of microstructure and mechanical properties of the samples before and after tests were characterized by scanning electron microscope (SEM), optical microscope (OM), X-ray diffractometer (XRD) and hardness tester. Results showed that strain strengthening occurred in high manganese austenitic cryogenic steel HM400 during tensile deformation. Moreover, HM400 steel possessed poor stress corrosion resistance in liquid ammonia medium, and hence it was not suitable as high parameterization and lightweight materials of liquid ammonia storage and transportation containers.