Processing of polymer-derived ceramic composite coatings on steel

Polymer-derived ceramic composites are being investigated as environmental barrier coatings to protect stainless steel from oxidation and carburization. Coatings have been produced using poly(hydridomethylsiloxane) as a preceramic polymer and titanium disilicide as an expansion agent. Processing parameters have been optimized and a relationship has been derived to predict the final coating thickness based on slurry viscosity and dip coating withdrawal speed. Microstructural analysis reveals a composite coating of oxidized filler particles in a silica matrix. A diffusion layer is visible at the coating-steel interface, indicating good bonding. The optimized coatings are similar to 18 mu m thick, and have some residual porosity and a density of 2.56 g/cm(3).