Microstructure and properties of diamond/Ni-based alloy composite coatings by induction brazing

The diamond/BNi-2 alloy composite coatings with different diamond particles were prepared on the surface of a 65Mn steel matrix by using induction brazing. The microstructure and phase composition of the brazed joints were analysed, and the formation mechanism of the diamond/brazing interface was uncovered. The wear resistance of the coating was investigated, and the wear reinforcement mechanism of the coating was elucidated. The results showed that the phases in the brazing coating are mainly Ni4B3, (Ni, Fe) solid solution, Ni3Si2 and CrB phases. The metallurgical reaction between the diamond and the brazing alloy occurred on the surface of the diamond, and the distribution of C elements at the diamond/brazing alloy interface promoted the emergence of a double-layer carbide structure, including the Cr3C2 on the diamond side and Cr7C3 on the surface of Cr3C2. When the diamond particle size is 200 mesh, the wear rate of the composite coating is 0.22 g/h, indicating the coating exhibiting excellent wear resistance. The diamond plays a vital role in blocking the expansion of the plough groove during the wear process, and the failure mechanism of the coating is attributed to the nickel-based alloy wear and diamond shedding.