In addition to requiring the reasonable cooperation of the substrate with sufficient strength and toughness in the work, the surface properties of the die are critical to the work performance and service life of the die. These surface properties refer to: wear resistance, corrosion resistance, friction coefficient, fatigue properties. The improvement of these properties, the improvement and improvement of the matrix material is very limited, but also uneconomical. However, surface treatment technology can often achieve a multiplier effect, which is also the reason for the rapid development of the surface treatment technology.
The surface treatment technology of the mold is a systematic project to change the morphology, chemical composition, structure and stress state of the mold surface to obtain the required surface properties through surface coating, surface modification or composite processing technology. The surface treatment can be divided into: chemical methods, physical methods, physical and chemical methods and mechanical methods. Although new processing technologies for improving the surface properties of dies are emerging, nitriding, carburizing and hardening film deposition are mostly used in mold manufacturing.
The nitriding process includes gas nitriding, ion nitriding and liquid nitriding. In each nitriding method, there are several kinds of nitriding techniques which can meet the requirements of different kinds of steel workpieces. Because the nitriding technology can form a surface with excellent performance, and the nitriding process has good coordination with the quenching process of the die steel, and at the same time the nitriding temperature is low, the nitriding needs no intense cooling, and the deformation of the die is minimal, so the die Surface strengthening is the use of nitriding technology earlier, but also the most widely used.
The purpose of mold carburizing is to improve the overall strength and toughness of the mold, that is, the working surfaces of the die has high strength and wear resistance. The technical idea introduced is to use lower grade material, that is, to replace higher grade material by carburizing and quenching, thus reducing the manufacturing cost.
The hard film deposition technology is currently more mature CVD, PVD. In order to increase the bonding strength of the film surface, a variety of enhanced CVD and PVD technologies have been developed. The hardened film deposition technology was first applied to tools (tools, cutting tools, measuring tools, etc.), and the effect was excellent. And variety of tools had applied hardened film as the standard process.
Dies have been coated with hardened film technology since the 1980s. Under the current technical conditions, the cost of the hardened film deposition technology (mainly equipment) is high, and it is still only applied to some precision and long-life molds. If the method of establishing heat treatment center is adopted, the cost of coating the hardened film will be greatly reduced. If more molds adopt this technology, it can improve China's mold manufacturing level as a whole.