Computational investigations of the bonding layer in CVD-coated WC+Co cutting tools

The effect of processing parameters on the bonding layer structure of the chemical vapor deposition (CVD) coated cemented carbide inserts was investigated through thermodynamics calculations. It was found that, under equilibrium conditions, the existing processing parameters would deposit graphite. To eliminate the thermodynamic driving force for the formation of graphite, the amount of the methane participating in equilibrium calculations must be significantly reduced. Under such circumstances, various titanium carbides formed instead, in agreement with recent experimental investigations. Thus the methane may have not fully cracked during the CVD coating process.