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What’s the vacuum brazing for diamond tools

Diamond woodworking tools have been widely used:
As a new type of composite material, polycrystalline diamond compact PDC has a development history of only more than ten years, but its application scope has expanded to all walks of life and is widely used in geological drilling, non-ferrous metals and alloys, hard Cutting processing of alloys, graphite, plastics, rubber, ceramics, wood and other materials.
Its surface layer is polycrystalline diamond sintered from diamond powders with different particle sizes, which has extremely high hardness, wear resistance and long working life; the bottom layer is generally tungsten-cobalt carbide, which has good toughness. Provides good support for surface polycrystalline diamond and is easily brazed to various tools.
Generally, ultra-high pressure and high temperature sintering method is used to manufacture polycrystalline diamond-tungsten carbide composite sheets. As its scope of use expands and the requirements for its performance increase, the corresponding performance detection methods have also gone through a rapid development process and have become mature in terms of detection accuracy and effectiveness.
Diamond (PCD) woodworking milling cutters are 20-100 times that of carbide (tungsten steel) milling cutters. The processing accuracy can reach 0.005mm, which can achieve the roughness and precision of polishing. There is no need for polishing at all, and the processing efficiency is immediately increased by 10 times. The above is especially suitable for various molding processing occasions and complex shape processing.

Diamond vacuum brazing process
The diamond welding process is basically vacuum welding. This is because diamond can withstand temperatures up to 1,500 degrees Celsius in a vacuum environment, while graphitization begins at 800 degrees Celsius in an air environment. The biggest problem in vacuum brazing to weld diamond is the coating of solder paste. Different coating methods are used for different materials and finished product requirements.
There are many difficulties that need to be solved when diamond vacuum brazing: ① The brazing material is required to have good wettability and bonding strength to the diamond and matrix; ② The selection of vacuum brazing materials and vacuum brazing processes must ensure the stability of the diamond, so as to Reduce or avoid the erosion of diamond by solder; ③ Due to the large difference in thermal expansion coefficient between diamond and metal matrix, the welding residual stress is also large, reducing the strength of the joint; ④ The melting point of solder is higher than the working temperature of diamond tools. Therefore, we should look for metal (alloy) materials with lower melting points and close to the expansion coefficient of diamond as brazing materials, and then consider adding certain active elements to improve the wettability and affinity for diamond, so as to be able to bond diamond and satisfy the tire requirements. The purpose of body mechanical properties. In addition, key technologies such as the realization of diamond surface metallization, the matching and selection of surface metal and solder, and the selection of solder and gas media need to be further matured and optimized.

Advantages of diamond vacuum brazing
The efficiency and service life of diamond tools not only depend on how firmly the diamond abrasive grains are embedded, but also are related to the wear resistance of the matrix. The strength of the carcass itself, the distribution of diamonds in the carcass, the concentration of diamonds, etc. will all affect the wear resistance of the carcass. Therefore, how to achieve the ideal state of the carcass is also a noteworthy issue in future work.
Vacuum brazing technology can achieve chemical metallurgical bonding at the interface between diamond, binding agent (brazing alloy material) and metal matrix, with high bonding strength. Due to the high bonding strength at the interface, only a thin bond thickness is enough to firmly hold the abrasive grains, and its exposed height can reach 70% to 80%, making full use of the abrasives and greatly extending the life of the tool. and processing efficiency. Compared with traditional technology, the maximum allowable cutting edge value of diamond tools can be increased by more than 50%. Under the condition that the power consumption of the tool does not increase or decreases, the diamond consumption of the workpiece material per unit volume is reduced by more than half. Compared with electroplating tools, it also shows incomparable advantages.