Study on surface and mechanical properties of stainless steel plates with multiple shot peening and laser peening without coating

This article compares the effects of single and multiple SP treatments, as well as LPC and LPWC treatments, on the surface and mechanical properties of 304SS. Experimental data were generated to compare the surface conditions, microhardness, and tensile properties. The surface roughness of multiple SP and LPC treatments was similar and relatively low. The microhardness layer could be obtained 100% deeper in LP-treated samples than in SP-treated samples. The maximum microhardness reached on the surface of SP-treated samples is 30% higher than that of LP-treated samples. Tensile test results showed an almost 50% increase in strength for LPWC and multiple SP treatments. X-ray phase analysis revealed that a more intense alpha'-martensite phase was formed in triple SP treatments compared to single SP treatments. The analysis also revealed the formation of low amounts of alpha'-martensite due to local melting in both LPC and LPWC samples, with a reported broadening of the austenite peaks. Additionally, the work hardening effect likely offsets the detrimental surface conditions after SP and LPWC treatments, showing that multiple SP and LPWC surface treatments have beneficial effects in terms of mechanical and metallurgical properties. It has been revealed that LPWC exhibits better mechanical properties than LPC, and multiple SP treatments have better mechanical properties than single SP treatments.