In the past 10 years, the application of coating technology on cutting tools has been rapidly popularized, and coated tools have become an indispensable mainstream tool for cutting. At the same time, with the rapid development of cutting to high-speed cutting, strong cutting and dry cutting, higher requirements are placed on the performance of coated tools. This article provides an overview of the current state of tool coating technology, development trends, and the development of new coating technologies by Japan JFE Precision Co., Ltd.
First, the status quo of cutting tool coating technology
1. Types of cutting tool coating technology
The coating technology used for cutting tools is mainly divided into two major categories: PVD (physical coating) and CVD (chemical coating). PVD is further divided into vacuum coating, cathode vacuum sputtering and ion plating. When the coating technology is used for cutting tools, the processing temperature of the CVD process is close to 1000 °C. For cutting tools with sharp cutting edges, this high temperature will reduce the hardness of the tool base and cause deformation and damage; vacuum coating and cathodic vacuum plating The main problem with the process is that the bonding strength of the coating to the substrate is low; ion plating can obtain a coating with a high bonding strength at a lower processing temperature, which is very suitable for use in a cutting tool.
2. Ion plating equipment and its specialties
Ion plating is a coating technique that evaporates a metal material in a vacuum and ionizes it in a plasma to bombard it on a negatively biased article to form a coating film. A variety of ion plating apparatuses have been developed in the past, and HSD (hot cathode) type and AIP (single arc/multi-arc ion plating) type are widely used in the industry. The difference between the two devices is mainly due to the different composition of the evaporation source. Since AIP type ion plating has the advantages of easily obtaining a multi-element coating and a multi-coating using a plurality of metals and a high bonding strength of a coating, it has become a mainstream equipment in recent years. A disadvantage of the AIP type is that there are molten particles from the evaporation source in the ion plating layer. The presence of such particles deteriorates the surface roughness of the plating layer, and if it falls off, it becomes a plating defect and becomes a starting point for corrosion and wear. In order to reduce such coating defects, the magnetic field control of the evaporation source is improved, and the precision cathode is used to greatly reduce the size and number of molten particles, which has a good effect on prolonging the tool life, and the device has been commercialized.
3. Types and characteristics of general AIP coatings
Due to the different material properties and cutting conditions, the life of the coating varies greatly. Therefore, the applicable coating materials should be selected according to the cutting conditions and requirements to obtain the best quality and economic benefits. For example, when it is mainly required that the cutting tool has excellent wear resistance, TiN, TiCN, TiAlN coating materials are mostly selected. In recent years, the use of TiAlN coating materials for coated cemented carbide tools has increased significantly; in the cutting of non-ferrous metals such as copper and aluminum, coated tools have also used CrN coating materials with good anti-stick properties. Examples; in the stamping die, TiCrN coating materials are mainly used; the most used coating material for injection molds is TiN, but in recent years, the proportion of CrN coating materials with excellent corrosion resistance and resin adhesion resistance is increasing. . At present, from the purpose of protecting the environment, users have stopped using chrome plating technology and replaced it with CrN coating materials. The tint and ZrN coatings are gold-tone, very aesthetically pleasing, and are used in decorative coatings.
Second, the development trend of AIP coating for cutting tools
1. History of coating development
Coatings for cutting tools start with TiN coatings, and coating technology is widely used in many general-purpose products. Since strong cutting requires the use of coating tools with higher hardness and better wear resistance than TiN, TiCN and TiAlN coating materials have been developed. Due to the excellent properties of these coatings, their market has expanded rapidly. TiAlN coating has good oxidation resistance and is suitable for cutting of high hardness materials. TiCN coating has poor oxidation resistance, but has low frictional resistance and excellent anti-sticking performance. It is suitable for cutting of lower hardness materials. These two coatings have a tendency to be used separately around the HRC40. In recent years, the requirements for processing of heat-treated workpieces, high-hardness materials, and difficult-to-machine materials by cutting (or even dry cutting) have been increasing. In addition, the use of a coating material tool can cut the requirements from low hardness to high hardness. It is also very strong. In order to meet these requirements, it is being explored to develop coatings that are higher in grades than TiCN and TiAlN, and which are superior in wear resistance, oxidation resistance, and anti-sticking properties. It can be said that they have entered a new era of coating development. Japan JFE Precision Co., Ltd. has developed SX-2, which has excellent wear resistance and anti-sticking performance, SX-W for hard alloy tools and SX- for high-speed steel tools, which have significantly improved coating hardness and oxidation resistance compared to TiAlN coatings. H and other SX series coated tools are being commercialized.
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