Plasma sprayed ceramic coatings without and with epoxy resin sealing treatment and their wear resistance

Plasma sprayed aluminum oxide-based coatings (Al2O3) are mainly used as a wear resistant surface covers in mechanical applications. Previous studies have shown that abrasion wear resistance of these coatings can be significantly improved by applying a sealing treatment. It was reported that this improvement is mainly due to microstructural toughening which takes place via the sealing process. Therefore, this study was conducted in order to determine the influence of the microstructural characteristics governed by the spray system settings and epoxy sealing on the wear resistance of these coatings. Unsealed and epoxy resin sealed plasma sprayed specimens prepared from alumina as well as alumina-13% titania were studied. Abrasion wear resistance of these coatings was evaluated employing the standard slurry abrasion response (SAR) and the standard dry sand rubber wheel (DSRW) abrasion tests. The coatings microstructure was characterized by light microscopy and their worn surfaces were analyzed using scanning electron microscopy. Porosity, microhardness and surface roughness of unsealed and sealed coatings were also compared. It was shown that the abrasion wear resistance of the epoxy resin sealed coatings is significantly better than that of the as-sprayed coatings for both types of applied tests.