C2H6 as precursor for low pressure chemical vapor deposition of TiCNB hard coatings

Multilayered TiN/TiCN/Al2O3 hard coatings grown by chemical vapor deposition (CVD) are used for wear protection of cemented carbide inserts, applied for example in turning, milling, parting and grooving operations. Within this work, the TiCxN1 − x coatings have been further optimized with respect to their structure and mechanical properties by addition of BCl3 to the feed gas. The characterization of the coatings was done by light optical microscopy, glow discharge optical emission spectroscopy, X-ray diffraction, scanning and transmission electron microscopy, surface roughness measurements, nanoindentation and cutting tests. The increasing amount of BCl3 in the feed gas resulted in boron contents of up to 3.96 at.% in the coating, where careful adjustment of the BCl3 supply is necessary. By incorporation of boron, an increase of coating hardness due to an increasing density of structural defects was obtained. The grain size decreases for the highest boron content, while the structure changes from equiaxed grains to a fine lamellar structure. In milling and turning tests, an increased lifetime was obtained for coatings with low amounts of boron, compared to the TiCxN1 − x reference.