Control of the Mesostructure of Suspension Plasma-Sprayed Coating with Laser Surface Texturing: Application to TBC

Thermal barrier coatings manufactured either by atmospheric plasma spraying or electron beam physical vapor deposition are widely used in the hot-temperature sections of gas turbines to provide thermal insulation and corrosion protection. Recently, the suspension plasma spraying process has emerged for the manufacturing of thermal barrier coatings. Specific microstructures including columns can be deposited. A narrow window of optimal parameters remains an outstanding problem to produce the suitable microstructure. Lately, studies demonstrated that the substrate topography plays a significant role in the columnar structure formation. This study shows that the substrate topography obtained via laser surface texturing enables a regular columnar structure. The laser beam generates peaks and cavities regularly arranged on the surface. The plasma spray parameters were selected to produce columnar structures linked to the substrate topography. The suspension composition and coating microstructure were studied. Superalloy samples with bond coats were used as substrates. The results showed that the columnar coating microstructure can be adjusted by optimizing the laser process parameters. The improved coating structure had more than 500columns per mm(2). Substrate surface topography optimization and suspension plasma spraying can improve the performances of thermal barrier coating system.