Sliding wear behavior of air plasma sprayed Al2O3 coatings sealed with aluminum phosphate

In this investigation, aluminum phosphate was used to seal an air plasma sprayed alumina coating, the hardness, porosity, phase composition, microstructure, and the sliding wear performance of alumina coatings before and after sealing treatment were examined. The results showed that the aluminum phosphate can penetrate the interface between the alumina coating and the substrate. The microstructural features of the coatings such as pores, cracks, and gaps between splats were found to be filled with the sealant and the cross-sectional hardness of the sealed coating was increased from 962.7 ± 77.2HV0.3 to 1299.3 ± 70.2HV0.3. The critical load and sliding wear resistance of alumina coating can be greatly increased by aluminum phosphate sealing treatment. •Aluminum phosphate sealing can dramatically increase wear resistance of Al2O3 coating.•Aluminum phosphate sealing can increase the load bearing capacity of Al2O3 coating.•There are three regimes for the APS sprayed Al2O3 coating in sliding wear process.•Fatigue crack and micro-grind are two main sliding wear mechanisms for Al2O3 coating.