Isothermal oxidation characteristics of laser-treated Al2O3 + Sm2SrAl2O7 composite thermal barrier coatings

Abstract

A thermal barrier coating system with Al<inf>2</inf>O<inf>3</inf> + Sm<inf>2</inf>SrAl<inf>2</inf>O<inf>7</inf> composite top coat was developed on an Inconel 718 superalloy substrate by using an atmospheric plasma spray technique, and the coated samples are treated with an Nd:YAG fiber laser to improve the surface properties. The as-coated and laser-treated samples were subjected to high temperature isothermal oxidation test at 1100°C for 150 h duration. The surface of the oxidized samples showed the presence of dissociated SmAlO<inf>3</inf>, SrAl<inf>2</inf>O<inf>4</inf>, and Sm<inf>2</inf>O<inf>3</inf>. Thermally grown oxides (TGO) are found at the bond coat top coat interface of the samples. The oxidation kinetics is examined by monitoring weight gain at regular intervals. The electrochemical impedance behavior, oxidation mechanism, and TGO formation in the developed composite coatings are discussed in detail. © 2023 Wiley-VCH GmbH.