Microstructure and mechanical properties of the diamond/1045 steel joint brazed using Ni-Cr + Mo composite filler

Diamond grits were bonded to 1045 steel by Mo particles modified NiCr composite filler. The effects of Mo particle addition on the morphology, bonding interface, residual stress, and diamond grits' strength were studied. The results show that: adding of Mo particles changed brazed diamond joints' morphology and interface element distribution. An appropriate amount of Mo particles reduced the distribution of interfacial cracks. The composite filler brazed diamonds generated two layers of compounds with different morphologies on the surface; the internal layer was a loose Cr3C2 layer, and the external layer was the Cr9Mo21Ni20 compound. The Mo particles could suppress the segregation of the active element Cr to diamonds, thus affecting the size and morphology of the interfacial Cr3C2 layer. The Mo particles effectively improved the CTE mismatch between the filler and diamond grits, but the excessive addition decreased the plasticity of the filler alloy. Ni-Cr + 4 vol% Mo composite filler brazed diamond joints have optimal morphology and lowest residual stress, while diamond grits have the best strength. Grinding tests showed that brazed diamond joints on diamond grinding heads fabricated by Ni-Cr + 4.vol% Mo composite filler exhibited the best fracture resistance.