Microstructure and performance of brazed diamond segments with NiCr-x (CuCe) composite alloys

Novel multi-layer brazed diamond segments were fabricated using NiCr-x(CuCe) composite alloys. Differential scanning calorimetry curves of the composite alloys were measured and analysed. The microstructures of the alloy segments and surface topographies of the brazed diamond segments were characterised. Performance tests of the alloy segments and brazed diamond segments were performed. The undercooling degree of the Ni-Cr alloy in the composite alloy increased with the Cu-Ce alloy addition, which led to coarse NiCu-rich regions and Ni3Si phases. A brazed diamond segment with a 5% Cu-Ce alloy addition exhibited the highest wear resistance and machining performance and the best surface morphology after a wear test. An excessive Cu-Ce alloy addition led to a rapid decrease in wear resistance of the brazed diamond segment owing to the large number of coarse NiCu-rich phases falling off from the composite alloy. The mechanism of the reduction in thermal damage to diamonds by the Cu-Ce alloy is elucidated. Initially the Cu-Ce particles melted and mainly Ni atoms diffused into the Cu-Ce liquid, thereby leading to the formation of NiCu-rich regions and Ce2Ni7 and CeNi2 phases, which in turn promoted the diffusion. The melting temperature of the Ni-Cr composite alloy was significantly reduced by the addition of the Cu-Ce alloy.