Effect of Shot Peening Time on Δ/γ Residual Stress Profiles of AISI 304 Weld

delta ferrite and residual stress are known to affect the corrosion behavior of AISI 304 stainless steel welds. To improve the corrosion resistance of a weld, shot peening is often carried out. This study aimed to investigate the effect of shot peening time on the residual stress evolution in both delta ferrite and gamma austenite in a 304 stainless steel weld. The residual stresses of both delta and gamma phases were significantly transformed from tensile to compressive after shot peening, and in addition, their surface residual stress deviations were lowered as the peening time increased. The stress versus depth profiles revealed a distinct plastic zone and an effective peening depth. The full width at half maximum (FWHM) of both phases increased as the peening time increased, but that of delta reached to a near stable value at peening 4 min. The FWHM change might be an index of surface coverage of peening, depending on the alloy phases. The electrochemical testing showed that shot peening effectively reduced the corrosion current intensity (I-co(rr)) of the weld to a lower value than that in welds peened by other processes. Both the grain refinement and compressive stress enhanced the corrosion resistance of the weld.