Title: Influence of the variation of nitrogen flow on the structure, mechanical and tribological properties of TiAlVN coatings deposited by unbalanced magnetron sputtering

Abstract

Ti 6Al4V alloy is used for the manufacture of orthopedic implants and different parts in the automotive and aeronautical industry. However, its limited hardness and wear resistance has led to its surface modification through plasma nitriding and / or the application of hard coatings such as TiN, TiAlN and TiAlVN, among others, improving their tribological behavior. Most of the published works report TiAlVN coatings deposited from independent targets of Ti50Al50 alloy and pure vanadium or from TixAl y Vz alloy targets with high aluminum and vanadium contents. In this work, the development of a TiAlVN coating using a target of the Ti6Al4V alloy deposited on substrates of the same alloy was proposed using the unbalanced magnetron sputtering technique in order to eliminate the costly process of plasma nitriding, which normally takes place at temperatures between 600 and 800°C. The deposition of the coatings was performed by modifying the nitrogen flow with 0, 6, 7, 8 and 9 sccm and leaving the other process parameters constant. The effect of the modification of the N2 flow on the microstructural, mechanical and tribological properties was evaluated, finding that small changes in the N2 flow have a marked influence on the microstructure of the coating, passing from a biphasic coating α-Ti and β-Ti of the Ti6Al4V to a biphasic TiN + Ti2N for low nitrogen flows and finally to a single phase TiN coating for the highest nitrogen flow of 9 sccm. The increased flow of N2 in the mixture with argon led to a TiAlVN coating of less roughness and grain size, as well as greater hardness and wear resistance compared to Ti6Al4V, and even higher than the values reported in the literature for the TiN. These results demonstrate that this technological strategy can replace the plasma nitriding of Ti6Al4V.