Effect of temperature on the oxidation behavior of Al2O3 reinforced CoCrAlYTa coating by laser-induction hybrid cladding

Abstract

The 2 wt% Al2O3 reinforced CoCrAlYTa coatings (referred to as 2Al2O3-CoCrAlYTa) were manufactured by laser-induction hybrid cladding. And the oxidation behavior of the coatings was investigated using a thermogravimetric analyzer (TGA) at different oxidation temperatures (950 °C, 1000 °C, 1100 °C, and 1200 °C) in an air atmosphere with a test time of 200 min. The composition and microstructure of the oxide scales formed at different temperatures were characterized and investigated. Additionally, the microstructure evolution of the coating, failure mechanism of the oxide scales, and elemental diffusion at the different temperatures were also discussed. It was found that after oxidation, Al depleted zones appeared in the 2Al2O3-CoCrAlYTa coatings. When oxidation temperature was 950 °C, fine-equiaxed oxide grains were formed on the coating. Moreover, at 950 °C, 1000 °C, and 1100 °C, the oxide scales were intact, and no large voids were found in the oxide scale/coating interface. As the temperature reached 1200 °C, the oxide scale formed on the surface of the coating became thicker and consisted of an outer layer of fine equiaxial crystals and an inner layer of coarse columnar crystals, and large voids developed at the oxide scale/coating interface, causing the oxide scales to delaminate from the coating.