Wear and Corrosion Behavior of Diamond-like Carbon Coatings in Artificial Saliva

This study investigates the properties of diamond-like carbon (DLC) coatings deposited onto a Ti6Al4V titanium alloy using plasma-assisted chemical vapor deposition (PACVD). The research encompasses adhesion tests, hardness, surface characterization, as well as corrosion and tribological evaluations. Artificial saliva was employed as both the lubricating and corrosive medium. Microscopic examination revealed a uniform coating with a thickness of about 3.2 µm. Scratch test results indicated that the deposited DLC coating exhibited superior adhesion, lower frictional resistance, and reduced wear compared to the titanium alloy. The coating deposition increased the hardness of the Ti6Al4V alloy by about 75%. Friction coefficients, measured under dry and lubricated conditions, were approximately 80% lower for the DLC-coated samples. Corrosion studies revealed that both the coated and uncoated surfaces demonstrated typical passive behavior and high corrosion resistance in artificial saliva. For DLC coatings, the corrosion current density and the corrosion rate were reduced by 85%. Microscopic observations of wear tracks following tribological and scratch tests confirmed the inferior wear and scratch resistance of the titanium alloy relative to the DLC coating. Under both dry and lubricated conditions (with artificial saliva), the volumetric wear rate of the titanium alloy was over 90% higher than for the DLC coating.