Effect of the Adhesive Properties of Vacuum Ion-Plasma TiAlN Coatings on Wear Resistance in Friction

In this paper, we study vacuum ion-plasma TiAlN coatings with various structure morphology (single-layer and multi-layer with various layer thicknesses) that were deposited by arc evaporation on a 38Cr2MoAl nitrided steel substrate. A continuous nitrided surface layer of phase γ' (Fe, Al) 4 N (on uncoated steel) served as a standard for comparing the mechanical and tribological properties. It is noted that the decisive factor determining the wear resistance of the coating during friction is the weak adhesion of TiAlN coatings to the nitride layer of the substrate. Peeling and chipping of the coating during tribological tests leads to a change in the wear mechanism from oxidative to oxidative-abrasive, which intensifies the wear of steel samples. The morphology of the structure of ion-plasma coatings under these conditions is not significant. The adhesion strength of TiAlN coatings with the same structure on steel substrates with a nitrided and carburized surface was experimentally verified using the scratch-test method. The values of the critical load for chipping coatings were 3.42 N for the nitride substrate and 16.97 N for the carbide substrate. The obtained data indicate a close relation between the adhesion properties of the “coating–substrate” interface with the wear resistance of the coating. Therefore, in the applied issues of the choice of wear-resistant coatings for loaded friction units, the effect of the substrate must be assigned a high priority.