Al2O3-Y2O3 ceramic coatings produced by cathodic micro-arc electrodeposition and their high temperature oxidation resistance

Abstract

This paper reports a novel processing for alloy and ceramic coatings on a large cathode surface area. Electro-pulse deposition was used to deposit MCrAlY alloy coating on a Ni-based alloy, followed by cathodic micro-arc electrodeposition (CMAED) of Al2O3-Y2O 3 ceramic coatings. An electrolytic cell forms when electrolyte drips down to the surface of the cathode from the bottom of the anode. When a high electric field is applied to the electrolytic cell, dielectric breakdown occurs, generating micro-arc discharges. The hydroxyl compounds in the electrolyte are deposited on the cathode surface, and then sintered to ceramic coatings by the high energy released from the micro-arc plasma in a very short time. The microstructure, composition and phase of the ceramic coatings were studied by SEM and XRD. The results indicated that the as-prepared ceramic coatings have excellent adhesion to the MCrAlY alloy coatings. Oxidation tests at 900°C show that the high temperature oxidation resistance of the Al2O 3-Y2O3 ceramic coatings is superior to that of Al2O3ceramic coatings and MCrAlY alloy coatings.