Correlation between microstructural characteristics and the abrasion wear resistance of sealed thermal-sprayed coatings

Plasma-sprayed aluminum oxide coatings (Al2O3) are mainly used as a wear-resistant coating in mechanical applications. Previous studies have shown that both the abrasion wear resistance and the corrosion resistance of these coatings can be significantly improved by applying a sealing treatment. It was reported that this improvement is mainly due to the microstructural modifications which take place during the post treatment process. Therefore, this study was conducted in order to determine the influence of the microstructural characteristics on the wear resistance of these coatings, when different sealing treatments were applied to AISI 1020 thermal-sprayed specimens coated with alumina–13% titania. Abrasion wear resistance of these coatings was evaluated employing the standard rubber wheel abrasion test and the ball-on-disc test. The coatings microstructure was characterized and their wear mechanisms were analyzed by using scanning electron microscopy. Porosity and microhardness values were also reported. It was shown that the abrasion wear resistance of both the phosphoric acid sealed coatings and the epoxy sealed coatings are significantly better than that of the unsealed coatings.