AbstractLubricated sliding wear tests were carried out on various surface coatings that were deposited on AISI 52100 and M50 steel substrates. The coatings include titanium nitride (TiN) deposited via an ion plating process, an electroplated chromium termed thin dense chrome (TDC), and a vanadium carbide (VC) deposited via the Toyota diffusion (TD) process. The tests were carried out using a synthetic turbine oil at one sliding speed and stepwise loading until catastrophic failure of the coating occurred. Friction coefficients were measured throughout the test interval, which showed that the vanadium carbide coating produced the lowest values (less than 0·055). Furthermore, this coating process had the greatest load carrying capacity, followed by the ion plated TiN on the M 50 substrate. Optical and scanning electron microscopy revealed that each coating process exhibited a different wear mode. In the TiN and VC coatings, polishing occurred along with the formation of cracks perpendicular to the sliding direction. Portions of the TiN coating spalled off the substrate via a delamination process. The TDC coating exhibited only a polishing wear mode.MST/1691