TiCN Hard Coatings for Tungsten Carbide Cutting Tools

Functional thin and thick layers are technologically important since they enhance or change the surface properties of any material. However, the two-dimensional nature of these films and buried interfaces poses challenges in reliable analysis of these class of materials.

Metal cutting tools use cemented carbides like WC-Co (tungsten carbide in cobalt-rich matrix) with different CVD and PVD based coatings to improve the surface hardness, rigidity and wear resistance. These coatings are mainly transition metal nitrides and carbides like TiN, TiC, ZrN, VN, TiCN, TiAlN. 

In this application example, TiC/N, and Al2O3 layers on WC-Co layers are mapped with EDS. Fig. 1 shows the focused ion beam (FIB) cross section of the cutting tool edge. Top TiN coating layer is followed by Al2O3/TiN/TiCN/TiN and WC-Co as substrate. With EDS, we could differentiate changes in N composition between TiN, TiCN and TiN layers (Fig. 2). Additionally, ESPRIT analytical software from Bruker is able to deconvolute strongly overlapping Ti and N (Fig. 4) automatically.

Fig. 1: EDS map and SE image of different coating layers on tungsten carbide cutting tools, the surface is polished using focused ion beam milling (FIB).
Fig. 2: EDS map showing Ti, C and N distribution, from left: TiN/TiCN/TiN and TiC. EDS can easily distinguish the compositional change between light elements like C and N.
Fig. 3: EDS map of WC substrate and Co binder in super hard cutting tools.
Fig. 4: Automated deconvolution and quantification of Ti and N using the ESPRIT analytical software.