Chemical vapour deposition of chromium

The chemical vapour deposition of chromium and the partial transformation of chromium into chromium carbide on carbon-containing substrates such as tool steels was investigated.The process using CrCl₂ as the reactive gas is described. Of the different process parameters studied, the substrate composition was found to have an important influence on the nature and properties of the chromium layer. In the early stages of deposition the reaction is controlled by the exchange of Fe from the substrate for Cr. As the H₂ reduction process becomes increasingly important, a nearly linear relationship exists between the growth rate and the deposition time. The composition, structure, thickness, hardness, roughness, corrosion resistance and tribological properties of the coatings are described. Some applications of chromium coatings are also given.