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

Abstract

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.