The current research status of brazed CBN tools is that diamond tools are only suitable for processing non-ferrous metals, while CBN tools are suitable for the effective grinding of iron-group metals, which is a supplement to applicable processing objects. However, CBN is chemically very stable, and brazing is more difficult than diamond brazing. At present, there are far fewer reports about CBN brazing in domestic and foreign literature than diamond brazing.
The research on CBN brazing abroad started in the early 1990s. The brazing process is usually: First, a TiC film is deposited on the surface of the CBN abrasive by chemical vapor deposition (CVD) at a deposition temperature of 1000 ° C and a deposition time of 90 minutes. Then, the Ni-Cr alloy is used for vacuum induction brazing at 1040 ° C, and the Ni-Cr alloy brazing material can effectively wet the coated CBN abrasive particles, thereby successfully welding the coated CBN on the substrate . In addition, Cr-containing nickel-based solders (for example, Ni-P alloy: Ni90%, P10%) can also satisfactorily wet the coated CBN abrasive particles.
In recent years, China's Nanjing University of Aeronautics and Astronautics has also studied CBN brazing and made some progress. The process used is: Ag-Cu-Ti alloy is used as the brazing material (main component: 67% Ag, 20% Cu, 12% Ti), and it is heated to the brazing temperature (1000 ° C) in a vacuum resistance furnace. Cooling the time to room temperature with a furnace was successful. The scanning electron microscope, X-ray spectrometer and X-ray diffractometer were used to observe and analyze the microstructure and solder joint interface of CBN. It was found that the element Ti in the alloy solder diffused and enriched to the CBN surface, and formed acicular TiB2. TiN is a chemical-metallurgical combination of the interface between CBN abrasive particles and solder, which is the main reason for the good wettability and high bonding strength between CBN and Ag-Cu-Ti solder. Subsequent grinding comparison tests showed that the brazed CBN wheel has higher abrasive retention strength than the electroplated CBN wheel. Under the same grinding conditions, the grinding temperature of the single-layer brazed CBN grinding wheel is significantly lower than that of the electroplated CBN grinding wheel, especially under the condition of large cutting depth. Therefore, compared with electroplated grinding wheels, brazing wheels have obvious advantages in reducing the grinding temperature, increasing the bonding strength of the abrasive, and extending the service life of the grinding wheel.
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