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2004
Conference Paper
Titel
Stability of carbides in chlorine-containing high-temperature environments
Abstract
Thermally sprayed coatings containing high amounts of carbides are often used for erosion protection at elevated temperatures. Thus, high temperature stability of carbides is essential. Some impurities, like chlorine, reduce high temperature oxidation resistance of carbides drastically. High temperature stability of various carbides was investigated in air and in chlorine-containing environments. Thermogravimetric oxidation tests were performed on fine powders of Cr3C2, TiC, TiCN, and WC in air and in air containing 2000 vppm HCl at the temperature range of 200-800°C. Chlorine accelerated the oxidation of carbides and also lowered the starting temperature of the oxidation process. Cr3C2 was the most stable carbide in both atmospheres. Coarse Cr3C2 powder was isothermally exposed to air with and without addition of solid KCl. KCl accelerated oxidation of Cr3C2 significantly. The oxide layer formed in the presence of KCl was porous and brittle, whereas the oxide layer formed on Cr3C2 in air was dense.