Physicochemical Conditions of the Process of Diffusion Chromosiliconizing of Carbon Steels in a Chlorine Environment.

The package of the applied programs with base of the thermodynamic data is used and the theoretical analysis of physical and chemical conditions of complex- saturation carbon steel by silicon and chrome in medium of chlorine in the closed reactionary space is carried out at the lowered pressure of a gas phase. Simultaneous saturation of steel 40 with chrome and silicon in chlorine atmosphere for 6 hours at a temperature of 1323 K and a pressure of 102 Pa of the gas phase is carried out in this work. By means of the x-ray diffraction studies, it is found that, under the assumed conditions of saturation on the steel 40 surface, diffusion layer with thickness of 100-110 µm is formed, which corresponds to the phase of the corresponding chromium carbides Cr23C6 and Cr7C3 doped with silicon, and a solid solution of chromium and silicon in α-iron. The corrosion studies carried out in this work show that chromosilicide coatings applied onto carbon steel 40 are less stable in solutions of 10% hydrochloric and sulphuric acids, and the most stable in solutions of nitric acid. [ABSTRACT FROM AUTHOR]