Thermal barrier coating on metallic substrates by preceramic route

摘要

A low cost, easily processable, multi layered functionally graded ceramic coating of thickness ～1000 μm was developed to protect metallic substrates from the risk of thermal oxidation. It consists of a four layered functionally graded coating consisting of aluminide layer followed by an intermediate zirconia as thermal insulative layer, an alumina layer serving as buffer layer with the outer most high emissivity layer to provide the required emissivity. All the layers were brush coated and the specimens were cured at 150℃. The solar absorptivity and emissivity of the coating was found to be 0.82 and 0.88 respectively. 15CDV6 plate of 150 × 150 × 5 mm was coated with multilayer thermal barrier coating of thickness ～ 1 mm. The coated sample was subjected to a heat flux of 8.5 W/cm~2 for 1035 sees to evaluate the thermo-responsive behaviour of the coating. Maximum back wall temperature measured was 299℃. The coating methodology is simple compared to complicated plasma techniques which can be applied on complex shaped substrates and all operations are carried out at low temperatures, below 150℃ ensuring no deterioration of structural properties of the substrate.