Thermodynamic analysis of silicon deposition on ASTM P92 and AISI 4340 steels

Chemical Vapor Deposition in a Fluidized Bed Reactor (CVD-FBR) has numerous advantages compared to other surface modification techniques like good heat and mass transfer during the deposition process, temperature uniformity and high degree of mixing between the gases and fluidized particles involved. This technique has been used to obtain silicon coatings on ferritic steels, which improves the limited corrosion resistance of the substrate. Analysis of optimum conditions by means of numerical simulations for the CVD process of silicon deposition on the AISI 4340 and ASTM P92 steels has been presented in this work. The temperature and pressure effects, the silicon conversion factor starting from the precursors formed, as well as the possible equilibria taking place in the formation of the silicon coating have been studied based on the thermodynamic calculations carried out on the THERMO-CALC software tool.