CMAS-phobic and infiltration-inhibiting protective layer material for thermal barrier coatings
Shijun Meng, Lei Guo, Hongbo Guo, Yuanpeng Wang, Hongli Liu
Abstract
Calcium-magnesium-alumina-silicate (CMAS) corrosion has attracted special attention in the thermal barrier coating (TBC) field. At high temperatures when CMAS is melted, it is adhered to the coating surface and penetrates the interior severely destroying TBCs. In this study, a promising CMAS-phobic and infiltration-inhibiting material of GdPO<sub>4</sub> has been proposed, on which molten CMAS is hard to wet and penetrate. These desirable attributes are explained based on analyzing the material characteristics of GdPO<sub>4</sub> and its interface reaction with CMAS. GdPO<sub>4</sub> is demonstrated to have low surface energy, making molten CMAS hard to wet and adhere to the surface. When contacted with molten CMAS, a double-layer structured reaction layer consisting of an acicular upper sublayer and a compact lower sublayer is formed on GdPO<sub>4</sub> surface, which can impede molten CMAS spreading and penetration effectively. First-principles calculation results reveal that the reaction layer has low surface energy and low adhesion work with CMAS, which are favorable for molten CMAS-phobicity. Additionally, the formation of the reaction layer increases the viscosity of molten CMAS, which can drag the melt wetting and penetration. Hence, GdPO<sub>4</sub>, which exhibits excellent CMAS-phobicity and infiltration-inhibiting ability, is a promising protective layer material for TBCs against CMAS adhesion and attack.