Coated Cemented Carbide Process II

Based on traditional chemical vapor deposition (CVD) and physical vapor deposition (PVD), some new coating technologies are emerging.

3. Medium Temperature Chemical Vapor Deposition (MTCVD)

Medium temperature chemical vapor deposition (MTCVD) is a kind of new technology based on traditional CVD. It uses organic compounds with C-N atom group as the reaction of raw material, such as methyleneimine, trimethylammonium, to react with hydrogen (H₂), nitrogen (N₂), titanium tetrachloride (TiCl₄) at 700-900℃ and form Ti(C,N) different coating layer. The biggest advantage of this method is that it can effectively curb the generation of brittle η phase, which remarkably improves the strength, wear resistance, thermal shock resistance and other comprehensive properties. However, compared with PVD process, the coating internal stress is tensile stress, which greatly increases the possibility of the cracks.

4. Sol-Gel

Sol-Gel is also called α-Al₂O₃, which uses Aluminum isopropoxide (C₉H₂₁AlO₄) as precursor (precursor is also known as matrix, which is reactant in atmospheric chemistry) to manufacture α-Al₂O₃ with complete and compacted structure on the surface of tungsten carbide cutting tools matrix by sol-gel process. In addition, there are no obvious physical defects and weakening phase between coating and interface, cobalt (Co) element part of tungsten carbide diffuse in the coating layer, which improves the adhesive strength between matrix and coating layer further. Some related experiments show that the wear resistance and the lifespan of tungsten carbide cutting tools by sol-gel is much better than the uncoated.

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