Regulation of residual stress in TiAlN coatings by WC-co substrate surface treatment

Abstract

The surface properties of coatings, especially the residual stress, have a direct impact on the cutting performance and service life of coated tools. In this work, TiAlN coatings are deposited on WC-Co cemented carbide by cathodic arc method. Four surface treatments are carried out on the substrate before deposition, including un-treatment (UT), micro-blasting treatment (MBT), diamond grinding treatment (DGT), mechanical polishing treatment (MPT). The effects of substrate treatment on the surface morphology, mechanical properties and cutting performance of coated tools are studied. The surface morphology of the substrate determines the nucleation sites, which in turn changes the residual stress in the coatings. The order of residual compressive stress (absolute value) in the coatings is MBT > UT > DGT > MPT. In the depth direction, the residual compressive stress gradually increases from the coating surface to the coating-substrate interface. The MBT tools with high residual compressive stress have the high coating adhesion and nano-hardness, which can obtain the longest service life.