Wear, Corrosion, and Biocompatibility of 316L Stainless Steel Modified by Well-Adhered Ta Coatings

316L stainless steel (SS) is a widely used biomaterial with low cost, but the long-term safety of releasing metal ions and poor corrosion resistance have received sustained attention. In this paper, Ta protective coatings with increased thicknesses were deposited onto the 316L SS by plasma surface alloying with extended deposition time. The microstructure, wear and corrosion resistance in simulated body fluid, and the biocompatibility and osteogenic activities of the Ta coated 316L SS samples were investigated. The results showed that the Ta coating deposited for 10 min was composed of loose and brittle beta-Ta phase, while those deposited over 30 min were mainly made up of dense and tough alpha-Ta phase. Due to the formation of a thick diffusion layer at the coating/substrate interface, well-adhered Ta coatings with high adhesion values of 109.8 N and 105.7 were obtained at 30 and 60 min, respectively. Moreover, Ta coatings deposited at these two parameters possessed better wear and corrosion resistance than 316L SS and those for 10 and 120 min. The best wear and corrosion resistance were about 4 and 66 times higher than the 316L SS. The good performance could be attributed to the suitable thickness and good compactness of Ta coatings, as well as the thick diffusion layer. These factors not only endowed the Ta coatings with good adhesion to resist peeling off during the friction but also protected 316L SS against corrosion of the phosphate-buffered saline (PBS) solution. The Ta coatings deposited for 30 and 60 min showed better capacity for osteoblast adhesion, spreading, and proliferation than 316L SS, where the Ta coating deposited for 60 min was the best.