Application of the most popular PVD surface modifi

2022-08-01
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The application of PVD surface modification technology in molds

mold failure often begins on the surface of the mold, and the performance of the mold surface directly affects the service life of the mold. The performance requirements of die surface and core are different, which is difficult to be realized by changing materials or overall heat treatment of die. The practice has proved that the effective way to improve die performance lies in the correct selection of heat treatment method and surface treatment process besides the correct selection of machining method and die material. Mold surface treatment is one of the important basic processes to improve mold quality

with the rapid development of China's automobile and home appliance industries, higher requirements have been put forward for the mold industry. How to improve the processing quality and service life of molds has always been a subject of constant exploration. The surface modification technology is gradually becoming an important way to improve the quality and service life of molds because of its wide range of functions, good environmental protection and huge efficiency

in the past 30 years, many new science and technology have penetrated into the field of surface modification technology, which has led to the rapid development of the surface modification technology of molds, and various surface modification technologies have been developed. Chemical vapor deposition (CVD) and physical vapor deposition (PVD)

chemical vapor deposition is a process that uses gaseous substances to carry out chemical reactions on solid surfaces at a certain temperature, and generates solid-state deposition films on solid surfaces. For example, to obtain TiC film on the mold surface, the mold is heated to 900 ~ 1100 ° C, so that the titanium tetrachloride and the carbon of the mold material react on the material surface, and a layer of TiC can be formed on the mold surface after a certain period of time

physical vapor deposition (PVD) is a method of directly depositing the gas of the material to be coated (rich nitride or carbide) into atoms, molecules or ions directly on the surface of the substrate by various physical methods under vacuum. During PVD treatment, the heating temperature of the workpiece is generally below 600 ° C, which is of great significance for molds made of high-speed steel, alloy die steel and other steels

although chemical vapor deposition can improve the service life of the die, its process temperature is high, and heat treatment is required after deposition, resulting in large deformation of the die, so its use is greatly limited. Physical vapor deposition (PVD) has the characteristics of low treatment temperature, fast deposition speed and no pollution, which is very suitable for surface strengthening of molds

1 PVD surface modification technology

pvd is the process of depositing the material to be coated on the workpiece surface to form a film by physical methods. At present, there are three commonly used PVD surface modification technologies, namely vacuum evaporation, sputtering and ion plating

vacuum evaporation is at 1.33 × 1 0~~l.3 3 × 1 0。 Under the pressure of 4 PA, the deposited material is heated with a heat source such as an electron beam to evaporate, and the evaporated atoms or molecules directly form a deposition layer on the surface of the workpiece. However, direct evaporation of refractory metal carbides and nitrides is difficult and tends to decompose compounds. Vacuum evaporation is characterized by simple equipment, process and operation. However, due to low kinetic energy of vaporized particles, weak adhesion between coating and substrate, and loose coating, the impact resistance and wear resistance are not high. Vacuum evaporation is mostly used for surface coating of optical components such as lenses and mirrors, various electronic components, plastic products, etc. with the successful maiden flight of C919 large aircraft, it is not widely used in surface hardening.

sputtering coating is a method to ionize argon through glow discharge in vacuum, accelerate the bombardment of the cathode under the action of electric field, and deposit the sputtered particles on the surface of the workpiece to form a film. Sputtering can be used to deposit various conductive materials, including high melting point metals and compounds. If tic is used as target material, TiC coating can be directly deposited on the workpiece. Sputtering can raise the substrate temperature to 500 ~ 600 ° C, so it is only applicable to steel molds with secondary hardening at this temperature

ion plating is to ionize the gas or evaporated substance by gas discharge under vacuum conditions, and evaporate the evaporated substance or its reactant on the workpiece under the bombardment of gas ions or evaporated substance ions

The basic principle of

ion plating is shown in Figure L. The metal or alloy vapor is ionized by a glow discharge of an inert gas. Ion plating includes the heating, evaporation and deposition of coating materials (such as tin and TIC). When the evaporated coating material atoms pass through the glow zone, a small part of them will be ionized and fly to the workpiece under the action of the electric field. They will be radiated to the surface of the workpiece with the energy of several thousand electron volts, which can penetrate into the substrate to a depth of about several nanometers, thus greatly improving the adhesion of the coating. The non ionized evaporation material atoms will directly deposit a film on the workpiece. The sputtering of inert gas ions and coating material ions on the workpiece surface can also remove the pollutants on the workpiece surface, so as to improve the adhesion

if the reaction gas is introduced into the evaporation space, a metal compound coating can be deposited on the surface of the workpiece, which is reactive ion plating. Due to the plasma activation, the workpiece only needs to be coated at a low temperature or even at room temperature, which fully ensures the dimensional accuracy and surface roughness of the parts. Therefore, it can be arranged to be carried out in the last process after the workpiece is quenched and tempered. For example, when depositing tin or tic, the substrate temperature can be selected in the range of 150-600 ° C. when the temperature is high, the hardness of the coating is high and the adhesion with the substrate is also high. The matrix temperature can be selected according to the matrix material and its tempering temperature. If the matrix is high-speed steel, 560 ° C can be selected. In this way, there is no need to worry about the reduction of matrix hardness and deformation for high-precision dies that have been quenched, tempered and processed to size. In addition, the deposition rate of ion plating is faster than that of other vapor deposition methods, and 10 μ For a tic or tin coating with a thickness of M, it usually takes only a few minutes

ion plating combines glow discharge, plasma technology and vacuum evaporation technology, which not only significantly improves the properties of the coating, but also greatly expands the application range of the coating technology. Compared with vacuum evaporation and vacuum sputtering, ion plating has the following advantages: 1) the film has strong adhesion with the workpiece surface, which is more durable and wear-resistant; 2) The ion diffraction performance is good, and it can be used for plating workpieces with complex shapes; 3) The film deposition rate is fast and the production efficiency is high; 4) A wide variety of coatings can be coated; 5) The film has stable performance and high security. Therefore, it has developed rapidly at home and abroad in recent years

2 development of PVD surface modified coating

the research and development of PVD coating technology in China began in the early 1980s. Tin coating initially coated by hollow cathode ion plating machine was used for high-speed steel tools and achieved good results. At the same time, tin coating is gradually used in stamping dies. However, because the working environment and influencing factors of the die are much more complex than those of the tool, the application of a single tin coating on the die is greatly restricted. In the 1990s, people improved the performance of tin coating on tools and dies through multi-component coating and multi-layer coating, and made great progress. According to the development process of the coating, the coating is divided into three generations: the first generation coating is a single-layer homogeneous coating, such as tin and tic, which has been applied in industrial and civil fields; The second generation of

is ternary composite coating, such as Ti (C, n) and (Ti, Al) n and Ti (B, n), which is under further research and has been applied to some wear-resistant parts; The third generation coatings are multicomponent composite coatings and multilayer coatings TiC/tin and Ti (C, n)/tin

in the 1990s, more and more attention has been paid to the basic research of physical vapor deposition tin in the world. Combining physical vapor deposition with other surface strengthening technologies to prepare composite coatings can further give play to the advantages of pvdtin coatings, such as gas nitriding and PVD, ion nitriding and PVD, electroless Ni-P and PVD. Due to the strong support of the intermediate transition layer, the adhesion, wear resistance and other mechanical properties of the composite coating have been greatly improved

3 application of PVD surface modification technology in molds

pvd surface modification technology can form a film with high hardness, high melting point, low friction coefficient, high corrosion resistance and high temperature oxidation resistance on the surface of molds, which is widely used in cold working molds, hot working molds and plastic molds

3.1 the application of PVD surface modification technology in cold working dies. The work of all kinds of cold working dies is to apply pressure on the processed materials at room temperature to make them separate or deform, so as to obtain parts with certain shape, size and performance. The most important failure forms of this kind of die are wear, fatigue, fracture and plastic deformation. To reduce the wear and fatigue fracture failure, the effective method is to modify the surface of the die to improve the hardness and wear resistance of the die surface, reduce the formation of fatigue cracks on the surface, and thus improve the service life of the die

Huijin technology coating Co., Ltd. uses PVD technology to apply TiCN coating to skdl stamping dies, which can increase the service life of dies by more than 5 times and solve the problems of die and product strain at the same time

wangjunli et al. Treated the cold stamping die "control arm flanging punch" (CRL 2mov) with PVD Ti/tin, and carried out practical application tests. The results show that the actual service life of the cold stamping die has increased from about 2500 times without PVD treatment to i]6650 times, that is, the actual service life of the die has been increased by about twice. Moreover, it is found from the failure morphology of the die after wear that the worn part is a smooth surface, belonging to gradual wear, No evidence of coating flaking. The results show that depositing Ti/tin coating on Crl2MoV steel can significantly improve the surface hardness and bearing capacity of Crl2MoV steel. Moreover, the double treatment of low-temperature plasma nitriding can improve the bonding condition between coating and substrate, and significantly improve the bonding strength between coating and substrate, which is attributed to the strengthening and toughening effect of Ti/tin coating and the strengthening effect of nitriding layer between towels

Dongfeng Motor Co., Ltd. and the State Key Laboratory of mold technology of Huazhong University of science and technology jointly developed the tin coating on the M16 hexagon nut punching die and piston pin cold extrusion die with multi arc ion plating equipment (PVD method) for surface modification. The die materials are w6m05cr4v2 steel. The uncoated nut punching die is severely worn during the punching process, resulting in the smaller size of the cutting edge and the smaller inner diameter of the punched nut. It is scrapped because it exceeds the limit, and the service life is only 5000 pieces (Times). After tin treatment, the anti-wear ability of the cutting edge is significantly enhanced. In case of failure, the wear band is narrow, especially the wear mark is obviously shallow. The service life reaches 25000 times, and the service life is increased by 4 times. The effect is very significant. The service life of piston pin cold extrusion dies and tin coated dies is about 1.7 times longer than that of uncoated dies, and the effect is also very significant

Harbin No.1 tool factory used multi arc ion plating technology (one of the PVD methods) to coat 4-6 μ Because of the high hardness, good chemical stability, low friction coefficient and small affinity of the tin residual layer, the adhesive wear that caused the scrapping of uncoated molds was almost eliminated and replaced by a small amount of oxidation wear, which increased the service life of the molds by more than 10. The effect is very significant

3.2 application of PVD surface modification technology in hot working die

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