Hard knives are the leading products of CNC machining tools. In some countries, more than 90% of the turning tools and more than 55% of the milling tools are made of carbide, and this trend is increasing. Carbide can be divided into ordinary hard alloy, fine grain cemented carbide and supercrystalline cemented carbide. According to the chemical composition of distinction, can be divided into tungsten carbide-based carbide and carbon (nitrogen) titanium-based cemented carbide.