2 Results and Discussion 2.1 The microstructure and properties of the coating 2.1 The Al2O3-TiO2 and WC Co cermet coatings are formed by overlapping particles. The coating structure is compact, without obvious cracks and coarse pores. It is composed of Al2O3, TiO2 and other phases, and also contains a small amount of Fe3O4, which is due to the high temperature of the arc zone and the oxidation of the material during the arc spraying process.
2.2 Friction and wear properties and surface microhardness The microhardness of the cermet coating is significantly higher than that of the matrix. The microhardness (Vickers hardness) of the Al2O3-TiO2 coating is the highest, reaching 1463, while the microhardness (Vickers hardness) of the matrix is only 524. Due to the formation of hard intermetallic compounds such as Al2O3, TiO2, WC and Co2O3 by surface deposition, the surface hardness of the plasma coating is significantly higher than that of the substrate. The wear resistance of the friction pairs of Al2O3-TiO2 and WC Co cermet coatings prepared by plasma spraying is significantly improved compared with that of untreated friction pairs, and the wear resistance of WC Co cermet coatings is slightly better than that of Al2O3-TiO2 cermet coatings, The reason why the plasma sprayed coating has high wear resistance is that it has high microhardness and nanocrystalline particles are dispersed in the coating. The high hardness coating is difficult to plastic deformation, and can not produce obvious brittle peeling under contact. The dispersed nanocrystalline particles have a good dispersion strengthening effect on the coating, Both of them improve the wear resistance of the friction pair.

When matching (selecting) various fluorine lined valves, try to understand and master the technical conditions for use, so as to select and use well and improve the service life of the valve. In case of exceeding the scope of technical conditions for use, it shall be proposed to the manufacturer for joint discussion.