Enhancement of adhesion and corrosion resistance of diamond-like carbon thin films on Ti-6Al-4V alloy by nitrogen doping and incorporation of nanodiamond particles

Pure diamond-like-carbon (DLC) and nitrogenated diamond-like-carbon (N-DLC) were deposited by Ion Beam Deposition using a low energy End-Hall Source on titanium and silicon substrates. The beam energy used during the deposition had a mean value of 65 eV. The structure and composition of the films were investigated by visible Raman Spectroscopy and X-ray Absorption Spectroscopy (XAS). Hardness and Young's modulus of the coatings were measured by nanoindentation. Adhesion of the coatings to the substrates was measured by Rockwell C indentation tests. To investigate the corrosion property of the coatings, Tafel polarization tests were performed from -1.5 V to 1.5 V in 0.89% NaC1 solution using the Standard Calomel Electrode as a reference. In our studies, DLC deposited directly on bare titanium alloy (Ti-6Al-4 V) shows poor adhesion and premature delamination. Pre-deposited nanodiamonds on titanium substrate greatly enhance the adhesion. The films produced on nano-diamond pretreated substrates are dense, smooth, and uniform, and DLC films show an average hardness value of 11 GPa, slightly higher than N-DLC (with an average hardness of 9 GPa). Despite its relatively lower hardness, nitrogen doping increases both adhesion and corrosion resistance of DLC coating. (C) 2015 Elsevier B.V. All rights reserved.