Wear-Resistant Metalloid-Containing Coatings on Steels Obtained by Thermal Diffusion Saturation and Vacuum Deposition

Abstract

New two-layer wear-resistant coatings of the composite type “thermal diffusion layer – vacuum ion-plasma coating TiAlN” have been obtained, their durometric and tribological properties have been investigated in the paper. The study has made it possible to establish influence of preliminary thermochemical treatment of a steel substrate on the formation of surface thermal diffusion layers is significantly higher than on unhardened steel substrates. Thus, the nano-hardness of TiAlN 1 μm-thickness coatings on substrates with a carbonitride layer when indented to a depth of 0.1–0.9 μm, is 1.9 times higher, the elastic modulus is 1.7 times higher, the ductility index H / E * is higher by 13.0 %, the rate of elastic recovery H 2 / E * and the rate of plastic deformation resistance H 3 / E *2 – have been increased by more than 2.1 and 2.4 times, respectively. The fracture toughness has been increased by 4.5 times. Preliminary boriding of the steel substrate leads to an increase in the actually measured nanohardness of the coated surface up to 1.8 times, elastic modulus up to 1.8 times, H 3 / E *2 – up to 1.8 times, H 3 / E *2 – up to 1.8 times, surface hardness – up to 10.0 %, while maintaining or increasing the plasticity index H / E up to 8.0 % in comparison with the characteristics obtained by nano-indentation of the TiAlN coating on an unhardened steel substrate. The discovered phenomenon is associated with an increase in the contribution of the hardened substrate to the elastic restoration of the coating and the indentation response of the surface. The paper presents the results of practical application of the developed wear-resistant compositions.