CVD in a fluidized bed reactor:: a method of developing coatings at temperatures below 600°C

The technique of CVD in a fluidized bed reactor (CVD-FBR) has a useful application in obtaining a protective coating on a substrate using a low work temperature, less than 600 degrees C. In this way, ferritic steels such as P-91, P-92, or P-122 can be coated at temperatures that do not change their microstructural properties. Coatings improve the chemical properties of substrates and their high temperature durability in corrosive environments. The aim of this paper is a general review of the deposition, co-deposition, or modified deposition of several elements, such as Al, Si, Al/Si, and Al/Hf, that can form various coatings on ferritic steels at low temperature. Deposition on ferritic steel using CVD-FBR has been studied. The coatings obtained are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). In the Al and Al modified with Hf depositions, the coatings are composed only of (Fe,Cr)(2)Al-5 or (Fe,Cr)(2)Al-5 and (Fe,Cr)Al-3 intermetallic phases, depending to the experimental conditions. The Al/Si coating is formed by (Fe,Cr)(2)(Al,Si)(5), and, finally, the Si coating is composed of SiFe3 intermetallic phase.