First-Principles Calculations of Interfacial Structure and Properties between WC Substrate and TiN Coating Based on Density Functional Theory

Abstract

The excellent adhesion strength between the substrate and coating in the field of cemented carbide-coated tools is the crux of ensuring the durability of coated tools. The TiN coating is often used as a bonding layer to improve the bonding strength between the substrate and outer coating. Insights into detailed information on the interfacial properties between substrate and coating are essential for developing coating structures with optimal adhesion properties. Therefore, first-principles calculations were used to investigate the anisotropy of the elastic characteristics of WC and TiN as well as the bonding mechanism at the interface. The findings demonstrate that WC and TiN bulks have different symmetries in their anisotropy of elastic characteristics. WC(0001) and TiN(111) slabs can be well-lattice matched thanks to the low lattice mismatch ratio (2.7%). The HCP stacking mode has larger bonding energy than the OT and hole stacking modes in the interface structure with identical terminating atoms. The C-HCP-Ti interface forms covalent and ionic bonds, which is thermodynamically stable (γ = −1.127 J/m2) and has the highest bonding strength (Wad = 8.899 J/m2) among all interface structures. The results of this study provide a practical perspective for improving the mechanical properties of cemented carbide-coated tools.