Surface engineering - sol-gel alumina coatings for surface modification of stainless steel

Alumina coatings were prepared via sol-gel route and used to coat on the stainless steel (SS) in order to improve the oxidation resistance of the latter at high temperature. Investigations were carried out on the conversion of the alumina xerogel films into crystalline ceramic coatings either as neat films or coated on the SS substrates by means of heat treatment, and the resulting samples were characterised using fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques. It was found that the formation of crystalline alumina coatings depends on the heating temperature; γ-aluminium oxide is obtained at 850°C and significant amount of α-aluminium oxide are obtained at 1100°C.The coated substrates showed improved oxidation resistance at high temperature as examined by optical microscopy.