Preparation of MoS2-Ti(C, N)-TiO2 coating by cathodic plasma electrolytic deposition and its tribological properties

With the aim to modify the tribological properties of Ti6Al4V for engineering application, cathodic plasma electrolytic deposition (CPED) was performed to explore its feasibility of the preparation of MoS2 containing Ti(C, N) based coating in MoS2 particles-dispersed formamide based electrolyte. The phase constituents, morphologies, element composition and microstructure of the samples were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and optical microscopy (OM) respectively. The hardness distribution on the cross-section was tested. The ball-on-disk reciprocating sliding test was adopted to evaluate the tribological performance of samples, after which the wear tracks were measured by the step profiler to calculate the wear rate. SEM and EDX were also used to study the wear mechanism. Results show that MoS2-Ti(C, N)-TiO2 coating is synthesized by CPED on Ti6Al4V, with its thickness of ~23 μm. The addition of cationic surfactant, Dodecyl trimethyl ammonium chloride, in electrolyte promotes the deposition of MoS2 particles into the coating. The hardness of the coating reaches 1024 ± 58HV0.025, higher than that of the coating free of MoS2. Hardened regions in both samples with the depth of ~170 μm beneath the coatings, are attributed to the quenching effect of the substrate, make the hardness drop eventually from the coating to the substrate. Both coated samples show higher tribological properties. MoS2 incorporated in the coating, playing the role of lubricant and alleviating the wear damage, creates the extra promotion in tribological properties of the sample, significantly reducing the wear rate and friction coefficient to only 11% and 25% that of the bared Ti6Al4V respectively.