Phase transformations and micro cracks induced by hydrogen in cold-rolled and annealed AISI 304 stainless steels

The effect of hydrogen and stress on the phase transformation and surface cracking in cold-rolled and annealed AISI 304 stainless steels was investigated. Hydrogen was introduced by cathodic charging in 0.1 M H2SO4 + 1 g/L Na2HAsO4·7H2O. Scanning electron microscopy was used to observe structural changes and surface cracks of the specimens. X-ray diffraction analysis was used to investigate phase transformations in the uncharged and charged specimens immediately after charging or during aging. Cathodic charging can cause ε martensite phase transformation and aging after cathodic charging can induce the ε and α′ martensite transformation. There are a certain amount of surface cracks on the specimens surface after hydrogen charging or during aging. The surface morphology of the specimens is studied, and the mechanism of the hydrogen-induced phase transformation and the surface cracking formation in the charged specimens immediately after charging or during aging is discussed.