High-temperature tribological evaluation of Co-based lubricious oxides deposited by means of Suspension Plasma Spray

The lifetime of numerous structures within gas turbine engines or energy generation technologies is limited by the tribological performance of the employed materials and coatings due to a large number of complex contacting mechanical assemblies. Thus, there is a strong effort to develop advanced materials which can withstand such harsh conditions, particularly at elevated temperatures. Owing to their high-temperature stability, oxide-based materials and coatings are promising candidates to enhance wear resistance and meet the demanding requirements at elevated temperatures. Some metal oxides present a brittle-to-ductile transformation under certain temperature conditions, changing their abrasive nature to solid lubricant. In particular, Co-based oxides have previously shown a significant reduction in the coefficient of friction and, therefore, reducing the general wear at elevated temperatures. However, the deposition and development of Co-based oxide coatings have received little attention. Thus, the main focus of this paper is to develop and tailor Co-based oxide coatings by means of suspension plasma spray (SPS) and critically examine their tribological behaviour at elevated temperatures. Ex situ analysis of the worn surfaces is performed using profilometry and microscopy, and the observations are correlated to friction and wear behaviour.