Principles and Applications of New Surface Treatment Technologies for Die Casting Molds!

Die casting molds are a large category of molds. With the rapid development of China's automobile and motorcycle industry, the die-casting industry has ushered in a new era of development. At the same time, higher requirements have been put forward for the comprehensive mechanical properties and service life of die-casting molds. It is still difficult to meet the constantly improving performance requirements solely through the application of new mold materials. Various surface treatment technologies must be applied to the surface treatment of die-casting molds in order to achieve high efficiency, high precision, and long service life for die-casting molds. Among various molds, the working conditions of die-casting molds are relatively demanding.
Pressure casting is the process of filling the mold cavity with molten metal under high pressure and high speed to form a die-casting mold. During the working process, it repeatedly comes into contact with hot metal, requiring die-casting molds to have high heat fatigue resistance, thermal conductivity, wear resistance, corrosion resistance, impact toughness, red hardness, and good demolding properties. Therefore, there is a high demand for surface treatment technology for die-casting molds. In recent years, various new surface treatment technologies for die-casting molds have emerged, but overall they can be divided into the following three categories:
(1) Improvement technology of traditional heat treatment process;
(2) Surface modification technology, including surface thermal expansion treatment, surface phase transformation strengthening, electrical discharge strengthening technology, etc;
(3) Coating technology, including chemical plating, etc.
The traditional heat treatment process for die-casting molds is quenching tempering, and surface treatment technology has been developed in the future. Due to the variety of materials that can be used as die-casting molds, the same surface treatment technology and process applied to different materials will produce different effects. Shikov recently proposed a substrate pretreatment technology for mold substrates and surface treatment techniques. Based on traditional processes, suitable processing techniques are proposed for different mold materials to improve mold performance and extend mold life.
Another development direction for improving heat treatment technology is to combine traditional heat treatment processes with advanced surface treatment processes to increase the service life of die-casting molds. If the chemical heat treatment method of carbonitriding is combined with conventional quenching and tempering processes to form NQN (i.e. carbonitriding quenching carbonitriding) composite strengthening, not only can higher surface hardness be obtained, but also the effective hardening layer depth is increased, the hardness gradient distribution of the infiltration layer is reasonable, the annealing stability and corrosion resistance are improved, thereby greatly improving the surface quality and performance of the die-casting mold while obtaining good core performance.