Trends and Perspectives in Mitigating CMAS Infiltration in Thermal Barrier Coating

The aerospace industry is facing challenges in meeting environmental and energy demands, which require a reduction in fuel consumption, emissions and production costs while improving the efficiency of aero-engines. One way to achieve this is by developing a thermal barrier coating (TBC) on the hottest components of the turbine to increase its inlet temperature. Different methods are used to deposit TBC, including air plasma spray (APS) and electron beam physical vapor deposition (EB-PVD), with each having its advantages and disadvantages. Current process developments are constantly trying to find a good compromise between intrinsic material properties, production cost and feasibility. With this in mind, suspension plasma spraying (SPS) has emerged as a viable option that can replace some applications. However, in service, complex loadings and environmental contaminants such as calcium-magnesium-aluminosilicate (CMAS) damage the TBC and reduce its durability. After presenting the SPS process, its application to thermal barrier coatings and industrialization challenges of the process, the chapter discusses the effects of CMAS infiltration on TBC and the methodologies used to characterize the damage during engine operation. Then, it explores potential solutions to mitigate CMAS attack, including modifying the coating composition, introducing additional layers, using SPS coatings and developing “CMAS-superphobic” surfaces.