Microstructural and Tribological Behavior of Suspension Plasma Sprayed Mixed Oxide (CuO &Ta2O5) Coatings

Mixed oxides have previously shown promising solid lubrication characteristics in severe contact conditions. Their favorable tribological behavior has generally been attributed to their outstanding chemical, thermal property and their ability to establish lubricious interfaces upon initial sliding. The main focus of this work is to identify the optimal composition of CuO/Ta₂O₅ systems in terms of tribological behavior when exposed to demanding conditions. Throughout this study, suspensions of mixed CuO/Ta₂O₅ oxides with various compositions have been prepared and subsequently deposited on carbon steel substrates by means of suspension plasma spraying (SPS) process. The effect of process parameters on deposition efficiency, microstructure, and composition of these coatings has been studied. In addition, the formation of the ternary oxide phase in flight and post-deposition on the substrate was investigated in more detail. The tribological performance of the deposited coatings has been evaluated under various conditions to provide a better understanding of the coating’s capability. Ex-situ analysis was performed by means of SEM and micro-Raman Spectroscopy techniques in order to identify the interfacial processes and the dominant wear mechanisms. The friction and wear behavior of the various coatings obtained from the tribological evaluation correlated well with the observations from the ex-situ analysis.