Reactions of Molybdenum and Tungsten Carbides with Oxygen at High Temperatures

The interaction of Mo2C, W2C and WC with O2 has been measured between 1300 and 2100 K and 10−4 and 40 mbar O2. The weight loss of the carbides is very similar to that of Mo or W, respectively. The reason for this is a metallic surface layer produced on the samples by a fast CO reaction. Its thickness is reduced again by the evaporation of volatile oxides. The superimposition of these two reactions finally results in a steady state with a constant layer thickness between 0.1 and 100 µm. The layer growth and steady state conditions can be calculated from literature data for binary systems. The theoretical values are in agreement with experimental results and show similar trends.