Coating the tool is one of the important ways to improve the performance of the tool. The emergence of coated cutting tools has made a major breakthrough in the cutting performance of cutting tools. The coated tool is coated with one or more layers of refractory compound with good wear resistance on the tougher tool body, which combines the tool substrate with the hard coating, so that the performance of the tool is greatly improved. Coated cutting tools can improve processing efficiency, improve processing accuracy, prolong tool life and reduce processing costs.

About 80% of the cutting tools used in new CNC machine tools use coated tools. Coated cutting tools will be the most important tool variety in the field of CNC machining in the future.

According to different coating methods, coated tools can be divided into chemical vapor deposition (CVD) coated tools and physical vapor deposition (PVD) coated tools. Coated carbide tools generally use chemical vapor deposition, and the deposition temperature is around 1000 °C. Coated high-speed steel tools generally use physical vapor deposition, and the deposition temperature is about 500 °C;

According to the different substrate materials of coated tools, coated tools can be divided into carbide coated tools, high-speed steel coated tools, and coated tools on ceramics and superhard materials (diamond and cubic boron nitride).

According to the nature of the coating material, coated tools can be divided into two categories, namely "hard" coated tools and 'soft' coated tools. The main goals pursued by "hard" coated tools are high hardness and wear resistance Its main advantages are high hardness and good wear resistance, typically TiC and TiN coatings. The goal pursued by "soft" coating tools is a low coefficient of friction, also known as self-lubricating tools, and its friction with the workpiece material The coefficient is very low, only about 0.1, which can reduce bonding, reduce friction, reduce cutting force and cutting temperature.

Nanoeating tools have recently been developed. This coated tool can use different combinations of various coating materials (such as metal/metal, metal/ceramic, ceramic/ceramic, etc.) to meet different functional and performance requirements. A properly designed nano-coating can make the tool material have excellent anti-friction and anti-wear functions and self-lubricating properties, which is suitable for high-speed dry cutting.

① Good mechanical and cutting performance: The coated tool combines the excellent properties of the base material and the coating material, which not only maintains the good toughness and high strength of the base, but also has the high hardness, high wear resistance and low wear resistance of the coating. coefficient of friction. Therefore, the cutting speed of the coated tool can be increased by more than 2 times than that of the uncoated tool, and a higher feed rate is allowed. Coated tool life is also increased.

② Strong versatility: Coated tools have wide versatility, and the processing range is significantly expanded. One coated tool can replace several non-coated tools.

③ Coating thickness: With the increase of coating thickness, the tool life will also increase, but when the coating thickness reaches saturation, the tool life will no longer increase significantly. When the coating is too thick, it is easy to cause peeling; when the coating is too thin, the wear resistance is poor.

④ Regrindability: Coated blades have poor regrindability, complex coating equipment, high process requirements, and long coating time.

⑤ Coating material: tools with different coating materials have different cutting performance. For example: when cutting at low speed, TiC coating has an advantage; when cutting at high speed, TiN is more suitable.

Coated cutting tools have great potential in the field of CNC machining, and will be the most important tool variety in the field of CNC machining in the future. Coating technology has been applied to end mills, reamers, drills, compound hole processing tools, gear hobs, gear shaper cutters, gear shaving cutters, forming broaches and various machine clamping indexable inserts to meet the requirements of high-speed cutting Steel and cast iron, heat-resistant alloys and non-ferrous metals and other materials.