Progress of surface engineering technology for mold manufacturing
mold materials are the foundation of mold industry, but even new mold materials are still difficult to meet the requirements of high comprehensive performance of molds. The use of surface engineering technology can make up for the shortcomings of mold materials to a certain extent. There are a wide range of surface engineering technologies that can be used in mold manufacturing, including traditional surface quenching technology, thermal diffusion technology, surfacing technology and hard chromium plating technology, as well as laser surface strengthening technology, physical vapor deposition technology, chemical vapor deposition technology, ion implantation technology, thermal spraying technology, thermal spray welding technology, composite electroplating technology, composite brush plating technology and chemical plating technology, which have developed rapidly in recent 20 years. The progress of rare earth surface engineering technology and nano surface engineering technology will further promote the development of surface engineering technology in mold manufacturing. Only rare earth surface engineering technology and nano surface engineering technology are introduced here.
1. Rare earth surface engineering technology
the addition of rare earth elements in surface engineering technology usually adopts chemical heat treatment, spray welding, vapor deposition, laser coating, electrodeposition and other methods
(1) the effect of rare earth elements on chemical heat treatment is mainly manifested in significant catalytic effect, which greatly optimizes the process; Adding a small amount of rare earth compounds can significantly increase the depth of the infiltrated layer and improve the microstructure and properties of the infiltrated layer. So as to improve the wear resistance, high temperature oxidation resistance and impact wear resistance of the mold cavity surface.
(2) using thermal spraying and spray welding technology, 3 Friction and wear testing machine: a relatively small amount of rare earth element can be added to the coating to obtain good structure and performance, so that the surface of the model cavity has higher hardness and wear resistance.
(3) the performance of the physical vapor deposition film is closely related to the bonding strength between the film and the substrate. The addition of rare earth elements is conducive to improving the bonding strength between the film and the substrate, and the surface density of the film is significantly increased. At the same time, adding rare earth elements can significantly improve the wear resistance of the film. For example, the superhard tin film applied to the mold performance (adding rare earth elements) makes the mold cavity surface show high hardness, low friction coefficient and good chemical stability, and improves the service life of the mold.
(4) the coating containing rare earth compounds can greatly improve the absorption rate of laser irradiation energy on the surface of mold metal materials, which is of great significance to reduce energy consumption and production costs, as well as to promote laser surface engineering technology. After laser treatment, the microstructure and properties of the rare earth coating are significantly improved, and the hardness and wear resistance of the coating are significantly improved. The wear resistance is 5 ~ 6 times that of 45 steel. Laser remelting of the thermal sprayed coating added with CEO 2 showed that the microstructure of the alloying layer was significantly changed and the grains were refined. The laser remelting hydraulic universal testing machine is mainly used for the tensile, contraction, bending and other mechanical properties tests of metal, non-metallic materials and parts, components and components. The spray welding alloy added with rare earth compound particles disperses and strengthens in it, reduces the energy of grain boundary, improves the corrosion resistance of grain boundary, and greatly enhances the wear resistance of mold cavity surface. Some literatures report that the wear resistance of rare earth elements is increased by 1 ~ 4 times. In addition, some studies have found that the effect of adding mixed rare earth compounds is better than that of single rare earth compounds.
(5) brush plating, electroplating and other electrodeposition methods can be used to add rare earth elements to the coating. The addition of rare earth glycyrrhizic acid complex can significantly improve the anti oxygen passivation life of the coating; Rare earth elements can catalyze the reduction of so 2, inhibit the oxidation of MOS 2 in ni-cu-p/mos 2 brush plating coating, significantly improve the antifriction performance of the coating, improve the corrosion resistance, and prolong the wear life of the mold cavity surface by nearly 5 times.
2. Nano surface engineering technology
nano surface engineering is a systematic engineering based on nano materials and other low dimensional non-equilibrium materials to strengthen, modify, ultra-fine process solid surfaces or give new functions to surfaces through specific processing technologies and means. Nano surface engineering technology has great application prospects and market potential.
(1) make nano composite coating. Nano composite coatings can be formed by adding zero dimensional or one-dimensional nano particle powder materials to the traditional electroplating solution. The CR DNP nano composite coating used for molds can prolong the service life of molds, keep the accuracy unchanged, and the coating is smooth and crack free after long-term use. Nano materials can also be used for wear-resistant composite coatings with high temperature resistance. If n-zro 2 nano powder material is added to the Ni-W-B amorphous composite coating, the high temperature oxidation resistance of the coating at ℃ can be improved, the corrosion resistance of the coating can be increased by 2 ~ 3 times, and the wear resistance and hardness can also be significantly improved. C o-dnp nano composite coating is used in more than 60 high-speed railway projects such as Beijing Shanghai, Wuhan Guangzhou, Wenfu, Chengdu Mianyang Leshan and Shanghai Kunming before and after the company's products at 500 ℃. Compared with Ni based and Cr Based Co based composite coatings, the high-temperature wear resistance of the workpiece surface is greatly improved. Nano composite coatings with excellent properties can also be prepared by adding nano powder materials to the traditional brush plating solution
(2) fabrication of nano structure coating is undergoing clinical trials in Germany and Switzerland. Thermal spraying technology is a very competitive method to produce nanostructure coatings. Compared with other technologies, it has many advantages: simple process, wide selection range of coating and substrate, wide variation range of coating thickness, fast deposition rate, and easy to form composite coating, etc. Compared with traditional thermal sprayed coatings, nanostructured coatings have significantly improved in strength, toughness, corrosion resistance, wear resistance, thermal barrier, thermal fatigue resistance and other aspects, and a coating can have the above-mentioned properties at the same time