Complementary Effect of Metal Shot Peening Over Deep Cold Rolled Ti-6Al-4 V Surface as a Two-Step Mechanical Surface Treatment

A two-step process of the mechanical surface treatments (MST) on Ti-6Al-4 V using a deep cold rolling (DCR) followed by a metal shot peening (MSP) was studied to understand the complementary effect of MSP over DCR. DCR was used for the introduction of higher and deeper compressive residual stress on the Ti-6Al-4 V coupons while MSP was used for the further improvement of the compressive residual stress near the surface of the coupons. The study shows that the two-step process reduces the anisotropy of Ti-6Al-4 V in both surface roughness and compressive residual stress compared the standard single step DCR process. Furthermore, the two-step process improves the near-surface compressive residual stress owing to the secondary MSP process without compromising the depth of influence by the first DCR treatment.