Effect of Laser Shock Peening on Properties of Heat-Treated Ti-6Al-4V Manufactured by Laser Powder Bed Fusion

Abstract

Ti-6Al-4V components fabricated by laser powder bed fusion (LPBF) suffer from high brittleness and poor toughness issues, which are largely attributed to the alpha '-martensite phase of LPBF products. Post-heat treatment is often carried out to improve the toughness of LPBF products, which, however, has been reported to result in a decrease in strength, abrasion resistance, and corrosion resistance. In this study, laser shock peening (LSP) is applied to post-heat-treated Ti-6Al-4V LPBF products as a solution to achieve enhanced surface properties as well as improved toughness. By post-heat treatment only the impact toughness of the LPBF-fabricated Ti-6Al-4V could be increased by 150%, that too at a significant degradation of surface hardness, wear, and corrosion resistance. When LSP is applied to the post-heat-treated Ti-6Al-4V, impact toughness remains nearly the same, whereas surface hardness and wear resistance are recovered to approximately 92% and almost full values prior to heat treatment, respectively. LSP also decreased the corrosion rate by 64% from that of the heat-treated sample. The results showed that LSP combined with post-heat treatment is a plausible approach to achieve both high impact toughness and enhanced surface properties in LPBF-fabricated Ti-6Al-4V products.