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.

The entry of hydrogen into the AISI 304 stainless steels can lead to α′ and ε martensite transformation and surface cracking formation.Figure optionsDownload as PowerPoint slideHighlights
► The mechanism of hydrogen-induced phase transformation in AISI 304 steels is studied.
► The effect of hydrogen on the surface cracking formation is investigated.
► The amount of martensite phases increase with an increase in hydrogen charging time.
► Less ε phase is formed in the charged cold-rolled specimens than in the annealed ones.
► The cracks propagate in the length and depth directions with hydrogen charging time.