Effects of humidity on tribological properties of 8YSZ/C coating designed by the combination of thermal spraying and hydrothermal reaction

Thermal spraying ceramic coatings have been widely used to prevent wear damage. However, the poor lubricating ability seriously restricted their application. In this article, zirconia stabilized by 8 wt% yttria (8YSZ)-C composite coating is prepared with the combination of in-situ synthesis carbon microspheres in the pores of as-sprayed 8YSZ coating by hydrothermal reaction. The chemical constituents and morphologies of the synthesized powders and the composite coatings are analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The microstructure and tribological behaviors of the composite coating are studied by SEM, TEM. and Raman analysis. The influence of humidity on the structural evolution of carbon microspheres during sliding wear process is discussed. The results show that the synthetic C powders exhibit a typical spherical structure. Meanwhile, carbon microspheres adhere to the pores of the 8YSZ coating. The friction and wear experiments in different humidity show that the re-graphitization of amorphous carbon becomes extremely obvious with the increase of humidity. Under the 80% humidity, an ordered graphene nanoscroll structure is formed, resulting in the optimization of the tribological properties. Furthermore, the friction coefficient of composite coating is reduced to 0.18, and its wear rate is about 1 times lower than that of under the 10% humidity. (© 2023 Wiley‐VCH GmbH)