Thermal stability and mechanical properties for ceramic composite films coated on steel by wet process

A ceramic coating slurry was designed, which suspended or dissolved ceramic components (silica, titania, alumina and kaolinite) and glass-forming components (alkali silicates and soda ash) in water. SiO₂-Al ₂O₃-TiO₂ based composite films (about 100 μm thick) were deposited on a steel plate by coating the slurry with a brush, followed by drying and calcination. The ceramic coatings obtained under proper conditions were found to exhibit excellent stability over a wide range of temperature. As evaluated by copper electrodeposition method, through-holes were present in the coatings calcined at 700°C or below, while they were eliminated completely after calcination at 1100°C in N₂. Vickers hardness of the coatings increased with increasing calcination temperature, while adhesive strength went through a sharp maximum at 800°C.