Post-processing of cold sprayed Ti6Al4V coating by laser shock peening

Cold spraying has emerged as a promising technique for repair and restoration of critical components made of Ti6Al4V alloy. However, as-sprayed Ti6Al4V coating often exhibit high porosity and weak adhesion strength, highlighting the need for post-treatment to enhance its integrity. Laser shock peening (LSP), being a well-controlled and high strain rate process, offers potential as a post treatment method to enhance properties of cold spray coating. However, the fundamental interaction between laser-induced shock wave from LSP and cold sprayed coating is not well understood. We found that direct LSP on as-sprayed Ti6Al4V coating results in a complete delamination of the coating due to dynamic tensile stresses generated by shock wave interaction. In contrast, LSP treatment on the heat-treated Ti6Al4V coating leads to coating densification, refined microstructure and increased adhesion strength. Porosity reduces by more than 90 % and adhesion strength experiences over a 2.2-fold increase after the treatment compared to the as-sprayed condition. This improvement is attributed to strain relaxation and microstructural alterations by post-heating which renders the surface more receptive to LSP impact. The findings signify the essential role of heat treatment in enabling the advantageous effect of LSP on cold-sprayed coating integrity.