Hardness, adhesion strength and tribological properties of adaptive nanostructured plasma-ion vacuum-arc coatings (Ti, Al)N–Mo2N

Abstract

The article reviews the properties of nanostructured multilayer coatings (Ti, Al)N–Mo2N obtained by plasma-ion vacuum arc deposition method (arc-PVD). The thickness of coating layers was comparable to the size of a grain, which was about 30–50 nm. Coating hardness reached 40 GPa with relative plastic work of deformation of about 60 %. It was found by the measuring scratching method that cohesive nature of coating destruction takes place entirely by a plastic strain mechanism, which was the evidence of its high viscosity. Local coating abrasion to a substrate level occurred at a load in the order of 75 N. Under test conditions as per «pin-on-disk» scheme using the opposing Al2O3 element at a load of 5 N, coating friction factor was equal to 0,35 and 0,50 at 20 °C and 500 °C respectively. Besides, it was practically not worn due to formation of MoO3 oxide in the friction zone (Magneli phase) which served as a solid lubricant. The increase in friction factor and appearance of significant wear were observed with further rising of test temperature. Such effect was due to intensified sublimation of MoO3 from friction surfaces with subsequent reduction of its lubricating efficiency.