Research On Induction Brazing Of Diamond With Crystal And Amorphous Ni-Based Brazing Alloy

The high melting temperature of Ni-based brazing alloy used to braze diamond could cause the thermal damage of diamond grits. In order to improve the wettability of diamond surface, alleviate the thermal damage of brazed diamond grits and enhance the bonding strength between diamond and Ni-based filler alloy, induction brazing was performed on diamond grits coated with NiCrBSi alloy deposited by physical vapor deposition(PVD) and induction brazing was proposed to braze the diamond grits and 45 steel substrates with amorphous Ni-based filler alloy. The processing performance of brazed diamond is improved by the two ways.In this study, brazed diamond bur was made as an example. The following innovative works were completed:(1) Amorphous NiCrBSi alloy film was evenly deposited on diamond grits by PVD. The film leads to the excellent wetting of brazing alloy toward diamond grits. Thus, bonding strength between diamond grits and brazing alloy is significantly enhanced.(2) Melting temperature of amorphous Ni based filler was about 957.1~1040.2℃. Amorphous phase has extremely narrow range of melting temperature and very short melting time. It can alleviate the thermal damage of brazed diamond grits.(3) After 140 minutes of grinding cast aluminum ZL102, temperature of process arc area of brazed coated diamond grits was about 35℃ lower than that of process arc area of brazed uncoated diamond grits. The rate of removal of cast aluminum ZL102 processed through brazed coated diamond grits was higher than that of cast aluminum ZL102 processed through brazed uncoated diamond grits because of low pullout percentage of brazed diamond grits and negligible change in hardness of cast aluminum ZL102.(4) The material removal rates and the temperature in grinding arc area of engineering ceramics ground by diamond burs were researched through grinding test, temperature change of brazed diamond burs with amorphous Ni-based filler alloy was not great, and that of brazed diamond burs with crystal Ni-based filler alloy was large. At the 90 th minute of grinding, temperature of process arc area of brazed diamond burs with crystal Ni-based filler alloy was about 25% higher than that of process arc area of brazed diamond burs with amorphous Ni-based filler alloy. At the feed load of 7.5N, the material removal rate of engineering ceramics by brazed diamond burs with crystal Ni-based filler alloy was about 42% less than that by brazed diamond burs with amorphous Ni-based filler alloy.In the study, many methods were combined to solve the difficult problem of thermal damage of brazed diamond. The application of diamond tools in the grinding machining was discussed. The coated diamond and the brazing filler metal were tried out in order to provide theoretical and experimental base for the widely application of the diamond tools in the future.