OBTENCIÓN Y CARACTERIZACIÓN DE RECUBRIMIENTOS DE ALUMINIO CON LA INCORPORACIÓN DE SILICIO SOBRE ACEROS FERRITICOS MARTENSITICOS (HCM-12A) MEDIANTE LA TECNOLOGÍA CVD-FBR

Protective coatings are often applied in order to increase the corrosion and oxidation resistance of ferritic-martensitic steels. In this study, Al-Si protective coatings were deposited by Chemical Vapour Deposition in a Fluidized Bed Reactor in atmospheric pressure (CVD-FBR) on HCM-12 ferritic martensitic steels. The initial process parameters were optimized by thermodynamic simulation using Thermocalc ® software. Then, those parameters were used as a first approximation in the experimental procedure to obtain the Al-Si coating. The coating was obtained at moderate temperatures in order to keep unchanged the mechanical properties of the substrate. A study of the microstructure and composition of the coating was carried out, using scanning electron microscopy with EDS and X-ray diffraction (XRD) techniques. Long term oxidation tests were performed during 1000 hours in 100% steam vapour atmosphere at 650 oC. The Fe–Al intermetallic coatings containing Si were obtained and these coating exhibited an oxidation behaviour far superior compared to the uncoated samples.