Effect of rare earth alloy addition on the microstructure and abrasion resistance of brazed diamonds with Cu-Sn-Ti filler metal

New brazed diamond specimens were prepared by adding different types of rare earth (RE) alloys to Cu-Sn-Ti filler metal. The microstructure and mechanical properties of the filler metal were characterized, and the interfacial characteristics and grinding properties of the brazed diamond specimens were analyzed. The addition of rare earth alloy (10% Cu-La alloy, 10% Cu-Ce alloy, and 10% Cu-Nd alloy) can improve the microstructure of the filler metal, reduce the number and size of holes and cracks in the filler metal, and improve the mechanical properties of the filler metal. The results of the grinding tests showed that the addition of the three rare earth alloys could improve the holding strength of the filler metal on the diamond grains, reduce the shedding rate of the diamond grains, and improve the grinding performance of the brazed diamond specimens. Compared with the other two rare earth alloys, the addition of 10% Cu-Nd improves the mechanical properties of the filler metal most significantly, and the best grinding performance of brazed diamond samples is obtained because there is no composite undercooling and aggregation of rare earth elements. The mechanism of rare earth alloy to improve the holding strength of filler metal to diamond abrasive grains was elucidated that the rare earth elements consume Cu and Sn elements in the filler metal, and the enrichment of Ti elements at the interface increases the thickness of the TiC interfacial layer. In addition, the reduction of cracks and holes in the filler metal decreased the defects around the diamond of the brazed specimen, effectively avoiding the rapid expansion of cracks along with these defects during the grinding process.