Effect of laser shock peening on the mechanical properties and cutting performance of TiSiN/TiAlN nano-multilayer coating

Coatings are widely used in the cutting tools due to their high hardness and the excellent wear resistance. However, under the challenge of extreme working environments, it is of great significance to enhance the mechanical properties and adhesion strength of coating/substrate system. In this study, the nanosecond pulse laser was employed to achieve the strengthening treatment of coated tools. The effects of different peak pressure of laser shock wave on the mechanical properties of the coatings were systematically investigated. The enhancement effect of coated tool was evaluated through nanoindentation tests, scratch tests and cutting experiments, while the underlying strengthening mechanisms of coating was analyzed. The results demonstrated that the lattice distortion and increased dislocation density within the coating structure could be attained after the laser shock peening (LSP) treatment, which contributed to the formation of residual compressive stress and the improvement of mechanical properties of coatings. Additionally, the adhesion strength of coating/substrate interface was improved after LSP treatment. The cutting performance of coated tools with untreated and LSP treated was evaluated after turning Ti60 titanium alloy. The flank wear value of coated tool with LSP treated was decreased. However, the mismatch of coating/substrate interface may occur under the condition of excessive LSP treatment, which could reduce the service performance of the coated tool. This study provided effective guidance into the strengthening mechanisms of coated tools by LSP treatment and the optimal process parameters could be obtained from the systematic research of the LSP experiments and cutting experiments.