Effect of Gd2O3 Addition on High-Temperature Oxidation Performance of NiCoCrAlYTa Coatings

Abstract

Herein, the effects of Gd₂O₃ on the laser cladding NiCoCrAlYTa coatings in terms of microstructure, phase structures, high temperature oxidation behaviors were investigated. The results showed that the addition of Gd₂O₃ changed the composition of coating phases, promoted homogeneous phase distribution, reduced porosity and improved coating density. During oxidation at 1100 °C for 150 h, the increase in the content of added Gd₂O₃ (at mass fractions of 0, 0.5, 1, 2, 5 and 10%) exhibited an initial inhibitory and then increased effect on the weight-gain rate of the coatings. Overall, 1% Gd₂O₃ addition resulted in the greatest improvement in the oxidation resistance of the coatings, with 49.58% decreases in oxidation kinetic constants, respectively, compared with those of unmodified coatings. However, at a Gd₂O₃ content of 10%, the thermally grown oxide on the coating surface exhibited large flaking areas. The high-temperature oxidation kinetic parameters of the coatings exhibited an inverted parabolic form with increasing Gd₂O₃ content. The higher Gd₂O₃ content led to the formation of excessive oxygen diffusion channels along grain boundaries, which is the reason for the decrease in the anti-oxidant performance of the coating.