Defects in VCD coatings on cemented carbide inserts for cutting tools

摘要

Anomalous growth of grains is often found in the CVD-coated layer on cemented carbide substrates. Carbide inserts of SNMN120408 coated in a commercial unit was examined. The coated film consisted of TiC, Ti(C, N) and Al_2O_3. The diameter of the anomalous grains protruding from the surface was about 10 to 30 #mu# m. The grins were investigated by the use of Auger electron spectrometry and it was foud that the anomalous grains consisted of Ti-C-O materials, which were buried under the TiC layer of the multilayer coating. This led to the conclusion that the materials came in the form of dust from the interior of the CVD unit. It is important to clean the interior of the unit at each time of coatings so as to achieve a sound coating because such growth can deteriorate the performance of the coated tools.