Mold material is the foundation of the mold industry, but even the new mold material is still difficult to meet the high comprehensive performance requirements of the mold. Surface engineering technology can compensate for the shortage of mold materials to some extent. The surface engineering technology that can be used in mold manufacturing is extensive, including traditional surface hardening technology, thermal diffusion technology, surfacing technology and electroplating hard chrome technology, as well as laser surface strengthening technology and physical vapor deposition which have been rapidly developed in the past 20 years. Technology, chemical vapor deposition technology, ion implantation technology, thermal spray technology, thermal spray welding technology, composite plating technology, composite brush plating technology and electroless plating technology. The progress of rare earth surface engineering technology and nano surface engineering technology will further promote the development of surface engineering technology for mold manufacturing. Only rare earth surface engineering technology and nano surface engineering technology will be introduced here.
   1. Rare earth surface engineering technology
   The addition of rare earth elements to surface engineering technology usually employs chemical heat treatment, spray spray welding, vapor deposition, laser coating, electrodeposition, and the like.
   (1) The influence of rare earth elements on chemical heat treatment is mainly manifested by significant infiltration and greatly optimize the process; adding a small amount of rare earth compounds, the depth of the layer can be significantly increased, and the microstructure and properties of the layer are improved. Thereby, the wear resistance of the surface of the mold cavity and the impact abrasion resistance against high temperature oxidation are improved.
   (2) Using thermal spraying and spray welding technology to add rare earth elements to the coating, good microstructure and properties can be obtained, and the surface of the mold cavity has higher hardness and wear resistance.
   (3) The performance of the physical vapor deposited film layer is closely related to the bonding strength of the film and the matrix. The addition of rare earth elements is beneficial to improve the bonding strength between the film and the substrate, and the surface density of the film layer is obviously increased. At the same time, the addition of rare earth elements can significantly improve the wear resistance of the film layer, such as the super-hard TiN film applied to the mold (adding rare earth elements), so that the surface of the mold cavity exhibits high hardness, low friction coefficient and good chemistry. Stability improves the life of the mold.
   (4) The coating layer containing rare earth compound can greatly improve the absorption rate of laser irradiation energy on the surface of the mold metal material, which is of great significance for reducing energy consumption and production cost, and promoting laser surface engineering technology. After the laser treatment of the rare earth coating layer, the microstructure and properties were significantly improved, the hardness and wear resistance of the coating layer were significantly improved, and the wear resistance was 5-6 times that of 45 steel. Laser re-dissolution of the thermal sprayed layer of CeO2 was carried out. It was found that the microstructure of the alloyed layer changed significantly and the grains were refined. Laser remelting spray-welded alloy after rare earth addition, the rare earth compound particles are dispersed and strengthened therein, reducing the grain boundary energy and improving the corrosion resistance of the grain boundary. The wear resistance of the mold cavity surface is also greatly enhanced. Some literature reports rare earth elements. Increased wear resistance by 1 to 4 times. In addition, studies have found that the effect of adding a mixed rare earth compound is superior to that of a single rare earth compound.
   (5) The rare earth element may be added to the plating layer by electroplating, electroplating or the like. The addition of rare earth glycine acid complex can significantly improve the anti-oxidation passivation life of the coating; the rare earth element can catalytically reduce SO2, can inhibit the oxidation of MoS2 in Ni-Cu-P/MoS2 brush plating, and significantly improve the coating. The anti-friction performance improves the corrosion resistance and extends the wear life of the mold cavity surface by nearly 5 times.
   2. Nano surface engineering technology
   Nano surface engineering is based on nanomaterials and other low-dimensional non-equilibrium materials, through specific processing techniques, processing methods, strengthening, modification, ultra-fine processing of solid surfaces, or system engineering to give new functions to the surface. Nano surface engineering technology is extremely promising and market potential.
   (1) Making a nanocomposite coating. A nanocomposite coating can be formed by adding a zero-dimensional or one-dimensional nano-point powder material to a conventional plating solution. The Cr-DNP nanocomposite coating for the mold can extend the life of the mold and maintain the precision. The coating is smooth and crack-free for a long time. Nanomaterials can also be used in high temperature resistant wear resistant composite coatings. If the n-ZrO2 nano-powder material is added to the Ni-WB amorphous composite coating, the high-temperature oxidation resistance of the coating at 550-850 °C can be improved to improve the corrosion resistance of the coating by 2 to 3 times, and the wear resistance and hardness are also improved. Both are significantly improved. Co-DNP nanocomposite coating is used, and the high temperature wear resistance of the workpiece surface is greatly improved compared with the Ni-based and Cr-based Co-based composite coating at 500 °C or higher. In the conventional brush plating solution, a nano-composite coating with excellent properties can also be prepared by adding a nano-powder material.
   (2) Making a nanostructured coating. Thermal spray technology is a very competitive method for making nanostructured coatings. Compared with other technologies, it has many advantages: simple process, wide coating and substrate selection, wide range of coating thickness variation, fast deposition rate, and easy formation of composite coatings. Compared with traditional thermal spray coatings, nanostructured coatings have significant improvements in strength, toughness, corrosion resistance, wear resistance, thermal barrier, and thermal fatigue resistance, and a coating can simultaneously have multiple properties as described above.