Thermobarrier and antifriction properties of triboceramics on the surface of a cutting tool with (TiAlCrSiY)N/(TiAlCr)N coating during high-speed dry cutting

Abstract

The physical mechanism of self-organization of a multilayer nanolaminated coating based upon non-equilibrium (TiAlCrSiY)N/(TiAlCr)N nitride on a cutting tool during high-speed (600 m/min.) dry cutting of N13 steel is established. Using a set of modern surface analysis methods coating degradation and tribo-oxidation are studied within the running-in and steady stages of wear. It is shown that during cutting, amorphous-nanocrystalline films of oxides similar to Cr₂O₃, TiO₂, Al₂O₃ (sapphire) and Al₂O₃ · 2 (SiO₂) (mullite) are formed within a wear crater. Using computer calculations by a finite element method, heat transfer is considered in the cutting zone during formation of protective tribo-oxides. It is found that among all tribo-oxides, mullite has the best thermal barrier properties. Oxidation is the main adaptation mechanism of a cutting tool under extreme mechanical and thermal shock during high-speed cutting. The topography of chip contact surface is studied at various cutting stages, which makes it possible to establish a change in plastic deformation mechanisms of treated metal and friction cutting modes. Quantum chemical calculations of the electron structure of mullite show the highest degree of its electron polarization and explain the radical drop in friction coefficient during film formation upon a wear surface. In this case, mullite acts as a solid lubricant.