Hydrogen Induced Cracks in Stainless Steel 304 in Hydrogen Pressure and Stress Corrosive Atmosphere

Abstract

The phenomena of hydrogen induced cracking (HIC) in 304 stainless steels was considered in a hydrogen pressure and stress corrosive atmosphere. Microstructures with chloride pits and stress corrosion cracks around the HIC were analyzed by SEM/EDS. Abnormal phase transformations induced by the hydrogen were analyzed using TEM and diffraction. In the hydrogen pressure atmosphere, pits and pores were observed on the surface of the 304 stainless steels. In addition, it was determined that Cl, an etchant component, was concentrated at a high concentration in the pits. SCC (stress corrosion cracking) was induced in the Cl atmosphere by stress caused by the abrasive embedded in the pits. It was assumed that the SCC mechanism is similar to HIC in that it occurs in the surface tensile stress and Cl atmosphere and is accompanied by grain boundary cracks similar to IGSCC (inter-granular SCC). The deformation induced phase transformation accompanied by planar slip should be related to the main cause of HIC in the hydrogen pressured atmosphere. Abnormal forbidden spots between the main diffraction spots were induced by the HIC in the hydrogen attacked area, where the microstructure was hardened. Understanding the HIC mechanism related to chloride corrosion can be used to assess the fitness of austenitic stainless steels for uses where there is a possibility of various susceptible cracking in hydrogen and chloride atmospheres.