Microstructure and processing performance of brazed diamond drill bits with Ni–Cr + Cu–Ce composite solder

Abstract

In this study, new brazed diamond drill bits and brazed samples were fabricated using Ni–Cr + Cu–Ce composite solder (i.e. Ni–Cr composite solder). The surface morphology and interfacial microstructure of the brazed samples that used Ni–Cr composite solder was characterised. The processing performance of the brazed diamond drill bits was evaluated and the surface morphology of the drill bits was analysed after conducting a drilling test. Results showed that the surface morphology of the brazed samples fabricated using Ni–Cr composite solder was better than that of its conventional counterpart using Ni–Cr alloy. Cr carbides (Cr3C2 and Cr7C3) were still obtained between the diamonds and Ni–Cr composite solder. When the amount of added Cu–Ce alloy exceeded a critical value, an increase in Cu–Ce alloy formed more brittle intermetallic compounds. The new brazed diamond drill bits with the Ni–Cr composite solder that contained 5 wt% Cu–Ce alloy achieved the longest tool life and highest drilling efficiency. The wear patterns of the aforementioned diamond drill bits were composed of grain micro fracture and macro fracture, which were the mildest wear types amongst all the drill bits.