The effect of interaction between the furnace atmosphere and the surface of cemented carbide substrate on the properties and performance of TiC coated cutting tools is described. It is shown that a highly decarburizing atmosphere during chemical vapor deposition (CVD) results in the formation of M12C eta phase and tungsten, and considerable diffusion of cobalt into the TiC film. This type of coating is shown to have a poor spalling resistance. On the other hand, a nondecarburizing atmosphere is shown to prevent the formation of tungsten, and diffusion of cobalt into the coating. Also, both M6C and M12C eta phases are found to exist under these conditions. The relative increase in the amount of M6C as compared to M12C is shown to improve the spalling resistance of TiC coating.

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