A Surface Conversion Treatment on a Borided and Cemented Seel Coated with Chromium Filme

Abstract

Coatings based on chromium borides and chromium carbides are commonly employed in applications requiring high hardness, low friction coefficient, as well as corrosion resistance. In this work, we made layers of chromium borides and chromium carbides on the surface of low carbon steel through some specific treatments. For chromium borides, the boriding treatment in a solid medium at 900°C for 4 h was followed by chromium electroplating on the steel surface and finally the application of annealing treatment at 950°C for 1 and 2 h. For chromium carbides, the cementation in a solid medium was followed by electroplating of chromium on the surface and finally the application of annealing treatment in the temperature range between 500 and 1100°C for 1 h. The results showed that, in the first case, boron diffusion and chromium deposition led to chromium borides on the treated surface. Similarly, for the second case, the cemented layer and the chromium deposited on the surface combined to form chromium carbides on the treated surface after annealing. The characteristics of the chromium borides and chromium carbides obtained were very similar to those of chromium borides and chromium carbides obtained by other processes.