Roughening Design of Anti-Cracking Interface of Insulation Layer for Titanium-Fire Retardant Coating

Titanium alloys are widely used in aero-engines. Titanium fire will occur under extreme situations, such as intense impact and friction, consequently causing fire all over the whole engine. An effective way to avoid the accident is to coat fire-resistant coatings on titanium alloy. This fire-resistant coating consists of a ceramic thermal insulation layer and a metal-based abradable seal layer. However, cracking may occur at the interface between the ceramic layer and the metal layer during service. Given that, this study aimed to enhance the crack resistance based on surface roughening design of the ceramic layer. Firstly, the heating and speeding processes of hollow and solid yttria-stabilized zirconia (YSZ) powders in plasma beam was investigated by simulation and experiment, and the dominant parameters regulating powder melting state were obtained. The rationality of simulation results was verified by the deposition of individual splats. Furthermore, surface morphology of the ceramic thermal insulation layer was tailored. Based on the simulation results, the main part of the thermal insulation layer was prepared under a higher spraying power with fully melted powders. In contrast, the surface of the thermal insulation layer was deposited by a lower power with semi-molten powders. In this way, a thermal insulation layer can be prepared to both have high inside thermal insulation and large surface roughness. This is beneficial to improve the interface adhesion between the ceramic layer and the metal layer, which would support the long-life protection of coating.