Regularities of tribooxidation and damageability at the early stage of wear of single-layer (TiAlCrSiY)N and multilayer (TiAlCrSiY)N/(TiAlCr)N coatings in the case of high-speed cutting

Abstract

We report a comparative study of single-layer (TiAlCrSiY)N and multilayer (TiAl-CrSiY)N/(TiAlCr)N PVD coatings on cutting tools during the break-in stage of high-speed dry cutting. Phase and chemical composition of tribooxides forming in the coating wear area were studied by X-ray photoelectron spectroscopy. It is shown that amorphous oxide films with a thickness of several dozen angstroms contain phases with a chemical composition close to mullite, sapphire, rutile, and chromium oxide. As a result of selective wear, the contact surface of the coatings retains the most durable tribooxides carrying out protective functions. Low-cycle fatigue resistance is studied using the cyclic microindentation technique. Fractal analysis of time-resolved indenter penetration depth curves combined with scanning electron microscopy (SEM) demonstrates phenomenological regularities of coatings’ damageability at the early stage of wear. It is shown that, in comparison with single-layer (TiAlCrSiY)N, the nucleation and growth of microcracks in a multilayer (TiAlCrSiY)N/(TiAlCr)N coating is accompanied by acts of microplastic deformation providing a higher fracture toughness of the (TiAlCrSiY)N/(TiAlCr)N multilayer nanocomposite.