Effects of gradient structure and modulation period on mechanical performance and thermal stress of TiN/TiSiN multilayer hard coatings

Gradient structure and modulation period of multilayer hard coatings are effective to improve the mechanical performance of cutting tools. However, the effects of gradient structure and modulation period on mechanical and thermal performances of hard coatings have not been clarified. In this study, seven groups of TiN/TiSiN multilayer coating models with diverse gradient structure and various modulation period were established using finite element method (FEM). Nanoindentation and cooling process were simulated to study the effects of gradient structure on mechanical performance and thermal stress. Coatings with thicker layers at the top have more excellent mechanical performance. Mechanical performance and stress concentration are both weakened with the increase of modulation period number, while stress fluctuation becomes more severe. Thicker layers at the upper and bottom of coatings cause maximum stress reduced during applied loads and thermal stress, respectively. Structure of decreasing-increasing modulation periods helps the coating to reduce stress impacts while having better mechanical performance.