Development of an internal diameter spraying system for CoNiCrAlY/YSZ thermal barrier coatings: microstructure, properties, and engineering verification

An internal diameter thermal barrier coating (TBC) system was developed using ID-HVOF for the bond coat and APS for the top coat to enable coating deposition within confined combustor and gas-duct geometries. Microstructural observations show that both layers exhibit uniform morphology, low porosity, and stable phase composition. The coatings demonstrate strong interfacial adhesion, high hardness, and excellent thermal-shock resistance, confirming their mechanical and thermal reliability. Furthermore, an engineering verification validated the system’s capability to produce continuous, defect-free coatings in restricted spaces. These results indicate that the proposed internal-diameter TBC process provides an effective solution for aero-engine components with narrow, complex inner surfaces.