Surface Treatment Technology of Die

In addition to the reasonable matching of high strength and toughness of the matrix, the surface performance of the die is very important to the working performance and service life of the die. These surface properties refer to wear resistance, corrosion resistance, friction coefficient, fatigue performance and so on. These improvements are limited and uneconomical only depending on the improvement of matrix materials. Surface treatment technology can often achieve twice the result with half the effort, which is the reason why surface treatment technology has developed rapidly.

Mould surface treatment technology is a system engineering that changes the shape, chemical composition, structure and stress state of the die surface through surface coating, surface modification or composite treatment technology, in order to obtain the required surface properties. From the way of surface treatment, it can be divided into chemical method, physical method, physical chemical method and mechanical method. Although new treatment technologies are emerging to improve the surface properties of dies, the main applications in die manufacturing are nitriding, carburizing and hardening film deposition.

Nitriding process includes gas nitriding, ion nitriding and liquid nitriding. In each nitriding process, there are several nitriding technologies, which can meet the requirements of different kinds of steel and different workpieces. Because the nitriding technology can form a surface with good performance, and the nitriding process has good coordination with the quenching process of the die steel, at the same time, the nitriding temperature is low, there is no need for intense cooling after nitriding, and the deformation of the die is very small, so the surface strengthening of the die is earlier and most widely used.

The purpose of die carburizing is mainly to improve the overall strength and toughness of the die, that is, the working surface of the die has high strength and wear resistance. The technical idea introduced here is to replace the higher level material with the lower level material, that is, carburizing and quenching, so as to reduce the manufacturing cost.

At present, CVD and PVD are mature technologies for hardening film deposition. In order to increase the bonding strength of the film workpiece surface, various enhanced CVD and PVD technologies have been developed. Hardening film deposition technology was first used in tools (cutters, cutting tools, measuring tools, etc.) with excellent results. Hardening film coating has been used as a standard process for many cutters. The technology of coating hardening film has been used in the die since 1980s. Under the current technical conditions, the cost of hardening film deposition technology (mainly equipment) is relatively high, and it is still only applied in some precision and long-life dies. If the heat treatment center is established, the cost of coating hardening film will be greatly reduced. If more dies adopt this technology, the level of die manufacturing in China can be improved as a whole.

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