High hardness and toughness potential TiN/TiSiN gradient nano-multilayer coating structure by finite element study

The low toughness and high brittleness of hard coatings are common defects that seriously affect their application in various fields. In order to ensure high hardness while increasing the toughness of the coatings, an evaluation model for the mechanical properties of TiN/TiSiN coatings has been established and validated by the finite element method. The effects of modulation period and modulation ratio on the hardness and toughness of TiN/TiSiN nano-multilayer coatings are investigated. Subsequently, a modulation ratio gradient structure is introduced to optimize the coating structure and thus achieve the toughening effect. The results indicate that the load on the low modulation ratio coating is distributed over a larger surface area and can resist greater loads, and that this structure has higher hardness and deformation resistance. However, the low modulation ratio structure produces a higher shear stress concentration region inside the structure. The modulation ratio gradient structure can take into account the advantages of low and high modulation ratios, it can ensure the high hardness of 34 GPa while dramatically reducing the maximum principal stress by about 46 %, and the maximum shear stress by 14 %, which effectively inhibiting crack formation and enhancing the toughness of the nano-multilayer coatings.