Self-lubricating design strategy for thermally sprayed ceramic coatings by in-situ synthesis of carbon spheres

Abstract

Conventional thermally sprayed ceramic self-lubricating coatings have significantly decreased their in-service stability and crack damage resistance due to their intrinsic brittleness and reduced mechanical properties resulting from tribological design. Herein, we successfully prepared a series of yttria stabilization zirconia (YSZ)-carbon coatings by combining in-situ carbon synthesis with thermal spraying technology. The influence of hydrothermal reaction temperature on the microstructure, mechanical properties, and tribological behavior of composite coatings has been investigated. Results indicate that carbon spheres grow in-situ within the inherent defects of YSZ coatings. With the gradual increase in reaction temperature, the size, degree of crystallinity, and graphitization of synthetic carbon spheres increase continuously. In addition, the composite coating exhibits outstanding mechanical properties, with the hardness and cohesive strength of the coating improved by 18.2 % and 62.3 %, respectively. Moreover, the composite coating prepared at 280 °C has the best tribological properties: the coefficient of friction is reduced by 77.1 % to 0.22, and its wear resistance property has been significantly improved, with the wear rate dropping from 6.35 × 10−4 to 8.75 × 10−7 mm3 N−1·m−1. A well-covered lubricating film composed of carbon, YSZ, and alumina nanoparticles contributes to the improved tribological performance.