Die-casting mould is a tool for casting metal parts. It is a tool for completing die-casting process on a special die-casting die forging machine. Basic process of die casting is that liquid metal is first filled into cavity of mould at low or high speed, and mould has a movable cavity surface. It is forged under pressure with cooling process of liquid metal, which not only eliminates shrinkage defects of blank, but also makes internal structure of blank reach broken grains as forged. Comprehensive mechanical properties of blank have been significantly improved.
 
Die-casting mould is one of major types of mould. With rapid development of China's automobile and motorcycle industry, die-casting industry ushered in a new era of development. At the same time, it also put forward higher requirements for comprehensive mechanical properties and service life of die-casting mould. Luo Baihui, Secretary-General of International Mold Association, believes that it is still difficult to meet ever-increasing demand for service performance only by application of new die materials. In order to meet requirements of high efficiency, high precision and long life of die-casting moulds, various surface treatment technologies must be applied to surface treatment of die-casting moulds. Among all kinds of moulds, working conditions of die casting moulds are more stringent. Pressure casting is to make molten metal full of mould cavity at high pressure and speed. It contacts with incandescent metal repeatedly in working process. Therefore, it is required that die casting mould has high thermal fatigue resistance, thermal conductivity, wear resistance, corrosion resistance, impact toughness, red hardness, good demoulding and so on. Therefore, requirement of surface treatment technology for die casting mould is high.