A study of the adhesion between CVD layers and a cemented carbide substrate by AEM analysis

The interface between chemical vapor deposition (CVD) coated layers and cemented carbide substrate of coated cemented carbide inserts was analyzed by analytical electron microscopy (AEM). This analysis was carried out from the viewpoint of the adhesion of the coated layer. From the results of elemental analysis, it became clear that the amounts of W and Co diffused from the substrate into the coated layer were different among three coating conditions. A columnar TiCN grain produced in relatively low temperature scarcely contained these elements, and they were detected only at the grain boundary. On the other hand, these elements diffused inside the grains when the shape of the grain was granular as TiN. Strong adhesion of coated layer was obtained when a proper amount of these elements was diffused. Coated inserts containing an interfacial layer with suitable diffused materials and main columnar TiCN layer showed good cutting performance.