Mechanical degradation of Fe-C-X steels by acidic stress-corrosion cracking

•In-situ tensile testing of Fe-C-X steels in acidic environment to assess SCC•Stress-corrosion cracks and reduced ductility and strength observed in acidic water•Anodic dissolution and hydrogen embrittlement contributed to mechanical degradation•Linear correlation between amount SCC embrittlement and corrosion potentials•SCC susceptibility increase by Mo2C and V4C3, decrease by tempering Fe-C-Cr (Cr7C3) This work evaluates the mechanical degradation of Fe-C-X (X = Cr/Mo/V) steels due to stress-corrosion cracking (SCC) in acidic aqueous environment. Tensile testing of as-quenched and quenched-and-tempered Fe-C-X steels in corrosive environment shows a reduced ductility and yield strength. Secondary stress-corrosion cracks and embrittled regions are detected by scanning electron microscopy. Anodic dissolution and hydrogen embrittlement mechanisms are elaborated to explain the mechanical degradation. A linear correlation between the amount of SCC embrittlement and measured corrosion potentials is obtained. Tempering Fe-C-Cr introduces Cr7C3 and increases the SCC resistance, whereas introduction of Mo2C and V4C3 realizes an increased reactivity and SCC susceptibility.