Analysis of the wear behavior of multilayer coatings of TaZrN/TaZr produced by magnetron sputtering on AISI-316L stainless steel

The AISI 316L stainless steel (316L SS) is commonly used in the orthopedic prosthesis field due to its mechanical properties, biocompatibility, and corrosion resistance. However, due to its high density and low wear resistance during sliding-contact operations, it may cause an allergic reaction due to the release of toxic ions and wear particles liberated during the sliding-contact operations. The modification of this class of metallic implants' surface characteristics represents the most common solution to change the surface's properties of the metal substrate, especially to improve the surface's mechanical and tribological behavior. DC magnetron sputtering (DCMS) is a suitable technique to deposit a layer with special characteristics due to its high control of deposition parameters, improving the film quality control. On the other hand, the binary (MN) and ternary (MXN) transition nitride coatings have shown promising results, especially the titanium (Ti), tantalum (Ta), and zirconium (Zr) nitride films, showing a high wear and corrosion resistance in mono- and multilayer arrangement. This technique can control the deposition time and temperature, working pressure, substrate rotation, the flux of gases, and the distance between the substrate and targets that modify the coating characteristics. This work presents the tribological analysis of the tantalum-zirconium-nitride/tantalum-zirconium (TaZrN/TaZr) multilayer coatings sliding-contact operations. Films with 7 and 11 layers were produced using DCMS, controlling the number and thickness of the layers' coating (LC) with the nitrogen injection to the work chamber. The films presented similar structures and chemical compositions. Similarly, the elastic modulus of both films was similar, but the 7LC coating exhibited a high harness (20 +/- 0.6) than the 11LC film (17.2 +/- 0.4). The variation of mechanical properties was reflected in the plastic deformation resistance (H3/E*2) and the elastic strain to the failure (H/E) ratios. Reciprocating sliding-contact tests carried out the tribological tests at applied loads of 0.5, 1, and 2N at dry conditions, employing an alumina (Al2O3) ball as a counter-body. The 7LC coating presented a higher coefficient of friction (CoF) and wear rate than 11LC film at 0.5N and 1N, but at 2N, the 11CL film was detached from the surface, increasing the wear rate value. On both films, the wear tracks presented a high material transference that produces a protected layer of tantalum oxide (Ta2O5), as was observed in the Raman spectra.

Automated summary

The study demonstrates that using DC magnetron sputtering to deposit binary and ternary nitride transition films on the surface of 316L stainless steel can enhance its wear and corrosion resistance. The number and thickness of the coating layers can affect its hardness and coefficient of friction.