The surface-enhancing technology in the mold manufacturing refers to the professional strengthening technology that the surface of the working part of the mold is pre-treated and then processed through a single or composite surface technology so that the mold working part can obtain the required surface or comprehensive performance. The advantages of the technology, such as its functionality, environmental protection, and synergies, play a particularly important role in mold manufacturing costs, mold quality, and mold life. In production, comprehensive consideration of the characteristics of the technology, the working conditions of the mold and the economics of production and other factors, and selecting the best matching point of the various factors can significantly improve the life and quality of the mold and obtain outstanding economic benefits. Research on Application of Surface Strengthening Technology for Die Working Parts 1. Application Status of Surface Strengthening Technology in Mould Manufacturing 1.1 Carburizing surface chemical heat treatment Carburizing process is a more commonly used (above 80%) mold surface hardening technology, which is mainly aimed at surface hardening of plastic mold cavity. After the carburizing treatment of the mold work parts, can achieve "external hard internal toughness" effect, that is, the work surface surface to obtain the hardness, The wear resistance, fatigue strength and other properties are improved, while the core part still maintains the original plastic toughness and strength, which meets the requirements for the use performance of mold working parts. It has fast infiltration speed, deep penetration, low cost, and it has perfect binding performance between the penetration layer and the base part. Smooth transition between bonding layers. However, the operating temperature is high (900 to 950 °C), especially the ionized carburizing temperature can reach 1100 °C, and the corresponding heat treatment is required after carburizing, resulting in the possibility of deformation of the mold, so the high-precision plastic mold is not This technique is recommended. The temperature of gas carburization is generally 920-950°C. After comprehensive evaluation by Wang Rongbin's test, the most reasonable carbon content of the carburized layer is w(C)0.85%-0.95%, and the gradient of the carbon content from the outer layer to the inner layer should be evenly distributed. No coarse-grained martensite, too many Paralympic, reticulate carbides and black troostite are allowed in the quenched structure. Excessive carbon content can easily lead to the formation of meshed carbides and other malignant structures in the parts and components of the mold, affecting the quality and life of the mold. In the subsequent processing, stress concentration and cracking may occur. Ion carburizing temperature is generally 900 ~ 960 °C, compared with the gas carburizing, ion carburizing has the advantages of high efficiency, small deformation, pollution, can handle any shape of the mold surface, etc., is more suitable for plastic mold and stamping mold surface Enhanced processing applications. 1.2 Flame Surface Thermal Spraying Technology Thermal spraying technology is a very rapid development of new surface enhancement technology. It uses a heat source (arc, ion arc, flame, etc.) to heat the sprayed material to the molten or semi-molten state, atomize it, and spray it at a certain rate. The surface of the pretreated substrate, which depends on physical changes and chemical changes, combined with the substrate, can improve the wear resistance, corrosion resistance, and heat resistance of the mold parts, and is easy to operate and low in cost. In recent years, the application of the technology in the mold surface strengthening has been further developed and improved. The Guangzhou Nonferrous Metal Research Institute adopted the supersonic spraying of carbide technology to deepen the Cr12 stainless steel. The life of the mold is increased by 3 to 10 times. At the same time, the technology has also made great progress in the repair of molds. For example, Zhang Xianglin of the State Key Laboratory of Materials Forming and Mould Technology of Huazhong University of Science and Technology adopted the HVOF technique to prepare nanostructures on the surface of Cr12MoV mold steel. WC12Co metal ceramic coating, measured average coating shear strength of 150.8MPa, coating bond strength greater than 80 MPa, coating hardness greater than 1000HV. After using the HVOF technology to repair the cold extrusion die, it can fully meet the requirements of the enterprise. 1.3 Composite Surface Plating Technology Electroplating technology is a technique for electrochemically depositing metal or metallization on the surface of a substrate. Plating hard chrome and hard nickel is a traditional technique for the surface treatment of plastic molds in China. The technology is performed at near room temperature, mold performance is almost unaffected, and severe deformation does not occur. At the same time, the surface roughness of the electroplating layer is low and the hardness is increased to 800 HV. However, there are still many problems, such as: corrosion resistance is not high, groove, deep hole can not be processed, making its application in the mold is limited, can only be used to strengthen the wear resistance of ordinary plastic mold, does not apply Plastic molds with complex shapes and high corrosion resistance requirements. At present, composite plating is the most dynamic field of application of plating technology in the mold industry. Composite brush plating can intensify the surface of the mold cavity, and can also be used to repair mold cavity surfaces. It has been found that brushing an amorphous coating on the surface of the mold cavity (0.01 to 0.02 mm) can extend the service life by 0.5 to 1.0 times. There are many types of microparticles that can be added in the composite coating, and the parameter adjustment range is wide, and the operability is strong, which fully reflects the diversity and comprehensiveness of the coating. Yu Tongmin and Liu Guichang of Dalian University of Technology applied Ni-P-PTFE composite plating to the surface strengthening of UPVC pipe fittings to solve the obvious effect of UPVC material on the corrosion of the mold surface, achieving the comprehensive performance requirements such as wear resistance and corrosion resistance of the mold surface. , but its hardness is slightly lower. For this reason, Fan Huiyu of Harbin Institute of Technology, based on Ni-P, composites PTFE with SiC particles and applies it to glass fiber reinforced plastic molding dies. Practice has shown that it can increase its life span by about 10 times. 1.4 PVD, CVD, PCVD Surface Coating Technology Coating technology is also known as vapor deposition technology. It is the deposition of stable compounds with special properties on the surface of mold working parts to form a superhard coating, so that the mold working parts have excellent performance. The most frequently used stable compounds in industry are TiC, TiN, and SiN. Physical vapor deposition (PVD) is a practical technique for depositing a coating on the surface of a substrate after vaporizing the coating material by a physical method. The technology began to be applied in the early 20th century. It has developed rapidly in the last 30 years and has become a new technology with broad application prospects. It has gradually developed into an environment-friendly and cleaner-type trend. It is mainly used to manufacture cold working molds with higher precision. . Jiangxi Science Institute of Applied Physics, Peng Wenxuan and Zhang Deyuan used multi-arc ion plating method to test the service life of 20 cold extrusion punches treated with TiN coating and found that their life expectancy increased by more than 1.5 times; the Institute of Nonferrous Metals, Guangzhou Song Sheng and Dai Mingjiang conducted detailed research on the application of physical vapor deposition hard film on the tool and die, and pointed out that this technology can significantly improve the service life of the die and the quality of the workpiece. However, the PVD method also has disadvantages such as poor plating and the like, and there is a limit to the processing of the surface of a mold part having a complicated shape. Chemical vapor deposition (CVD) is a practical technique for chemically reacting a gas at the surface of a substrate material and forming a coating layer at a temperature ranging from 900 to 2000°C. This technology has a high deposition temperature and a strong coating bond. There is almost no requirement on the surface shape of a mold part. For example, a complex shape or a part with a groove and a small hole can be evenly coated to make up for the related defects of physical vapor deposition, for example, The TiC coating often used in the mold surface strengthening has high hardness, good wear resistance, small friction factor, good anti-friction property, strong seizure resistance, and greatly improves the service life of the mold. However, the CVD method has a high processing temperature and still needs to be quenched, resulting in large deformation and other defects. Therefore, the use of this technology is limited in the manufacture of high-precision molds. Plasma-enhanced chemical vapor deposition (PCVD) is a practical technique that uses glow discharge to enhance the chemical activity of reactants, promotes chemical reactions between gas phases, and deposits high-quality deposits at low temperatures. It is a treatment method between CVD and PVD. . The PCVD method is used to plate the coating on the surface of the working part of the mold. It has been proved that the economic benefit is very considerable. Zhang Yecheng and Zhang Jin of Chongqing Institute of Technology studied the application of PCVD technology in mold strengthening. It was found that the deposition of a layer of TiC on the W18Cr4V cold extrusion die using PCVD technology can increase the life of the die by more than 10 times than that of the non-deposited film layer; The PCVD method can be used to increase the life of the die by 1 to 4 times for the plastic product mold. Prof. Tao Ye from Beijing University of Aeronautics and Astronautics prepared the PCVD Surface Strengthening Technology Research Laboratory, designed and manufactured test equipment and supporting facilities on its own, and received timely funding from the Natural Science Foundation of China. The project team developed the mold surface strengthening technology based on PCVD composite infiltration method, which has the advantages of low process temperature, good uniformity of plating, and high bonding force of the coating. It is applicable to the preparation of all high temperature tempering molds and some low temperature tempering molds. The only one is suitable for both tool hardening and shape recovery Hybrid mold surface strengthening by vapor deposition surface enhancement technology. It can be seen that the application of PCVD technology in the field of reinforcement of mold parts has been a success. And the application prospect is very broad. 1.5 High Energy Beam Strengthening Technology High energy beam strengthening technology has the comprehensive advantages of non-contact, precise and controllable, wide material adaptability, strong flexibility, excellent quality, resource saving and environment-friendly, and can be used for high-volume, high-efficiency and automatic production, and also suitable for multi-species, small-batch production. Processing, and even the customization of individual products, is an indispensable and important technology in the mold manufacturing industry. Among them, ion implantation technology has been widely used in cold work molds, hot work molds, and plastic molds for its almost perfect strengthening effect, and its average life can generally be increased by 2 to 10 times. Has significant application value. 2. Application Prospect of Surface Strengthening Technology in Mould Manufacturing According to the research, rare earth elements can strengthen the surface, increase the infiltration rate, and purify the stable grain boundary. At the same time, the surface structure, physical and chemical properties and mechanical processing properties of the mold parts are improved. The use of rare earth elements in the composite surface strengthening process results in more pronounced results. If rare earth is added to the Ni-Cu-P-MoS2 coating, the wear life of the mold cavity surface can be extended by nearly 5 times. In addition, rare earth elements have obvious improvements in chemical deposition, electrodeposition, spraying, and laser coating, but the effect is not yet stable. It can be seen that the application of rare earth elements to mold manufacturing will be an important direction for future research. With the rapid development of nanotechnology, it has a significant effect in improving the productivity and life of the mold. However, there are still many imperfections in this technology. There are still many tasks to be done, such as the inhomogeneous coating on the surface of the mold cavity, the unclear deposition parameters, and the unclear mechanism for surface enhancement of the mold parts. 3, the conclusion The surface strengthening technology of mold working parts can make up for some deficiencies of the current mold materials to a certain extent, and has shown a strong development potential. However, there are still some deficiencies in the current surface enhancement technology of mold parts, and its application is also affected by Certain restrictions, as long as the focus on research and development, will certainly accelerate and improve the application of surface hardening technology in the mold manufacturing process. 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