Corrosion and tribological properties and impact fatigue behaviors of TiN- and DLC-coated stainless steels in a simulated body fluid environment

In this study, the corrosion and tribological properties of TiN and DLC coatings were investigated in a simulated body fluid (SBF) environment. The ball-on-plate impact tests were conducted on the coatings under a combined force of a 700 N static load and a 700 N dynamic impact load for 10,000 impacting cycles. The results indicated that the TiN and DLC coatings could achieve a higher corrosion polarization resistance and a more stable corrosion potential in the SBF environment than the uncoated stainless steel substrate SS316L. The good corrosion protection performance of TiN could be due to the formation of a Ti–O passive layer on the coating surface, which protected the coating from further corrosion. The superior corrosion property of the DLC coating was likely attributed to its chemical inertness under the SBF condition. The TiN and DLC coatings also exhibited an excellent wear resistance and chemical stability during the sliding tests against a high density polyethylene (HDPE) biomaterial. Compared to the DLC coating, the TiN coating has a better compatibility with the HDPE. However, the impact tests showed that the fatigue cracks and the coating chipping occurred on the TiN coating but not on the DLC coating.