Tribological Performance of Chemically Bonded Phosphate Ceramic Coatings with Different Curing Agents on Mild Steel

To enhance the compactness of the chemically bonded phosphate ceramic coatings (CBPCs), different inorganic curing agents (MgO, CaO, and ZnO) are selected as the reinforcement. Tribological experiment and the analysis of microstructure, phase characterization and mechanical performance are carried out to clarify the mechanism of different curing agents on the effect of wear performance. It is found that the curing agents place a significant role on the wear performance of the coating. Compared with coating without curing agents, more bonded phase (AlPO4) can be detected when curing agents (MgO, CaO) are used, which is mainly resulted by the high heat release from MgO and CaO related reactions, and this released heat energy enhances the formation of AlPO4. The results indicate that the morphology and tribological performance of CBPCs using different kinds of curing agents are dependent on the weight ratio of AlPO4 to α-Al2O3 (defined as RPA). The suitable value of RPA will not only improve the bonding strength among the ceramic particles, but also decreases the quantity of defects (such as pores). Upon the above results, CBPCs with MgO process superior wear resistance due to their dense and uniform microstructure.