Tool material selection

The material used to make the tool must have high high-temperature hardness and wear resistance, necessary bending strength, impact toughness and chemical inertness, good processability (cutting, forging and heat treatment, etc.), and not easy to deform. Usually, when the material hardness is high, the wear resistance is also high; when the bending strength is high, the impact toughness is also high.

However, the higher the material hardness, the lower its bending strength and impact toughness. High-speed steel is still the most widely used tool material in modern times because of its high bending strength and impact toughness, as well as good machinability, followed by cemented carbide. Polycrystalline cubic boron nitride is suitable for cutting high-hardness hardened steel and hard cast iron, etc.; polycrystalline diamond is suitable for cutting non-ferrous metals, as well as alloys, plastics and fiberglass, etc.; carbon tool steel and alloy tool steel are only used as tools such as files, dies and taps.

Cemented carbide indexable inserts have been coated with titanium carbide, titanium nitride, aluminum oxide hard layers or composite hard layers by chemical vapor deposition. The developing physical vapor deposition method can be used not only for carbide tools, but also for high-speed steel tools, such as drills, hobs, taps and milling cutters. The hard coating acts as a barrier to hinder chemical diffusion and heat conduction, slowing down the wear rate of the tool during cutting. The life of the coated blade is about 1 to 3 times longer than that of the uncoated one.