Silicon coating on ferritic steels by CVD-FBR technology F.J. Bolívar a , L. Sánchez a , S.A. Tsipas a , M.P. Hierro a , J.A. Trilleros b , F.J. Pérez a, ⁎ a Grupo de Investigación de Ingeniería de Superficies y Materiales Nanoestructurados, Spain b Grupo de Investigación en Ingeniería Metalúrgica, Universidad Complutense de Madrid, Facultad de Ciencias Químicas, 28040 Madrid Spain Available online 9 November 2006 Abstract Silicon protective coatings were deposited on ferritic steels (9–12% Cr) by chemical vapour deposition by means of fluidized bed reactor (CVD-FBR). The process was performed at temperatures below 580 °C with the use of Silicon donator powder and hydrogen chloride (HCl) of activator. Thermodynamic calculations were made before the experimental study to investigate the conditions for the formation of gas precursors for the deposition of the Si coating. The samples were examined by means of optical microscopy (OM), Scanning Electron Microscopy (SEM), Energy Dispersion Spectroscopy (EDS) as well as X-ray diffraction, and the results, show the formation of dense, homogenous and thin coatings consisting of Fe 3 Si. © 2006 Published by Elsevier B.V. Keywords: Silicon deposition; Chemical vapour deposition; Silicides; Ferritic steel 1. Introduction The use of surface coatings is an important alternative as a means of extending the performance of materials in a wide range of applications. Materials exposed to high temperature in an oxidizing environment may suffer from corrosion and/or oxidation, with subsequent depletion in alloy elements, affecting their mechanical properties. The application of protective coatings is therefore interesting to shield the materials from such corrosive environment. Addition of silicon to metals and alloys, including steels, generally increases the corrosion, oxidation and erosion resistance[1]. Addition of silicon to alloys increases oxidation resistance. Unfortunately, addition of silicon also changes the mechanical properties of the alloys and increases the cost of the materials [2]. However, application of silicon coatings can overcome this limitation, because it can improve the corrosion resistance of the steels without changing the mechanical properties of the bulk materials [3–5]. Many coating techniques have been used to obtain Si coating such as chemical vapour deposition (CVD), physical vapour deposition (PVD), pack cementation and ion implantation [6]. Chemical vapour deposition is one of the most important processes to obtain Si coating, especially in the microelectronic industry. The aim of this work is to study the possibility of obtaining Si coating on ferritic steel with content of Chromium between (9–12% Cr) by means of chemical vapour deposition in fluidized bed reactor. The initial parameters of the process were obtained by thermodynamic simulation realized with Thermo- calc software [7]. Then, the results were used to select the initial conditions for the experiment to produce Si coating, at low temperature under atmospheric pressure. 2. Experimental 2.1. Substrate materials The composition of ferritic steel used as base materials for Si diffusion coating is presented in Table 1. The samples (10 mm × 20 mm × 2.5 mm) were polished from 240-grit SiC paper up to 600-grit SiC paper, and then ultrasonically cleaned in alcohol, dried and weighed prior to coating experiment. 2.2. Coating procedure 2.2.1. Thermodynamic calculation Thermodynamic studies of phase equilibrium (composition, partial pressure) during CVD were performed using the Surface & Coatings Technology 201 (2006) 3953 – 3958 www.elsevier.com/locate/surfcoat ⁎ Corresponding author. Tel.: +34 91 39 44215; fax: +34 91 39 33457. E-mail address: fjperez@quim.ucm.es (F.J. Pérez). 0257-8972/$ - see front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.surfcoat.2006.08.101