Vacuum Brazing Diamond Grits with Cu-based or Ni-based Filler Metal

Diamond grits were brazed using Cu-Sn-Cr and Ni-Cr-B-Si filler metals, and the brazed grits were examined for microstructure (SEM, EDS, XRD), microhardness, and compression strength. Results showed that the microstructure of the Cu-based filler metal was uniform and consisted of α-Cu + (α-Cu + δ). Its wettability to the diamond was better than Ni-based filler due to the formation of a thin carbide reaction layer that improved the bond strength between the diamond and steel. The Cu-based filler led to reduced thermal damage to the diamond. The Cr in the filler metal diffused to the steel substrate to form a reaction layer at the filler/steel substrate interface. The microhardness of the Ni filler metal (810-830 HV0.3) was significantly higher than that of Cu filler metal (170-230 HV0.3). The compressive load values of the diamond grits brazed with Cu-based or Ni-based filler metal were 93.7 and 49.2% of the original diamond, and the TI values were 83.7 and 59.8% of the original diamond. Grinding experiments for failure mode in monolayer tools revealed that the tools brazed with Cu-based filler metal had a lower macro-fracture ratio than those brazed using the Ni-based filler.