Laser shock peening-induced surface gradient stress distribution and extension mechanism in corrosion fatigue life of AISI 420 stainless steel

[Display omitted] •Surface gradient structure was prepared by LSP with different pulse energies.•Effect of pulse energy on corrosion fatigue behaviour was studied.•LSP generated refined lath, carbide fragment and nano-sized precipitation•Corrosion fatigue life was increased by 29.28 % using gradient laser pulse energies.•The CFCG rate equation considering both pH value and gradient CRS was developed.•Corrosion fatigue cracking modes were determined by surface gradient structure. Surface gradient stress distribution was prepared on AISI 420 martensitic stainless steel (MSS) by massive laser shock peening treatment (MLSPT) with different pulse energies, and effects of MLSPT on residual stress and corrosion fatigue properties in NaCl solutions with different pH values were investigated by microstructural observation, residual stress measurement, corrosion fatigue test, and fractural morphology. Results showed that the coupling effect of MLSPT-induced surface microstructural evolution and gradient stress distribution effectively contributed to an extension in corrosion fatigue properties. Furthermore, the corrosion fatigue crack growth rate equation considering both gradient compressive residual stress and pH value was developed.