Influence of Inorganic Sealant in Hot and Cold Erosive Wear in Plasma Sprayed Alumina Coating

Plasma sprayed alumina coating is applied in many industrial applications in order to promote wear and corrosion resistance. Nonetheless, high porosity remained after deposition is a critical factor because it decreases the wear resistance. Some inorganic sealants can be used to reduce the open pores and superficial micro-cracks effect, improving the wear and corrosion resistance of alumina coatings. In this work, plasma sprayed alumina coating samples were divided into two groups: i) impregnated with inorganic sealant (AlPO4) and heat treated; ii) as deposited. Erosive wear tests were carried out in an erosion rig according to ASTM G76. The samples were subjected to an erodent flux, with impact angles of 30º up to 90º, at a velocity of 50m/s and temperatures of 25°C up to 400°C. The samples were characterized by SEM, Vickers microhardness, potentiodynamic anodic polarization and erosive wear rate. Results showed that erosive wear rate of alumina impregnated coating is lower than without the sealant. The sealed alumina coating presented higher mechanical properties; improved microstructural characteristics and the sealant promoted better lamellae contact, as can be observed by less sharpness in pits formation of microstructure.