Abstract

In this paper the oxidation behaviour of WC, Cr3C2, and TiC and their composites with binder metals is compared on the basis of literature data and some oxidation experiments. It was found that the oxidation mechanisms in air, which are more or less equal to service conditions of coatings, seem to be totally different from those in the spray process in the case of WC, but similar in the case of TiC and Cr3C2. Oxide layer scale adhesion strengths and, possibly, the high volatility of WO3 seem to be responsible for this difference. It can also be assumed, that the problem of oxidation of TiC-based materials and Cr3C2-NiCr is that of local oxidation on the surface of the spray powder particles during the spray process. Cr3C2-NiCr and TiC-based materials are characterized by a high oxidation resistance in air. Plain WC-Co oxidizes readily in the temperature range 400-600°C, but alloying with Cr, as for instance in WC-CoCr and WC-(W,Cr)2-Ni spray powders increases the oxidation resistance.

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