Microstructure and performance of brazed diamonds with multilayer graphene-modified Cu–Sn–Ti solder alloys

This study aims to improve the hardness of solidified Cu–Sn–Ti solder alloys and reduce the erosion of diamonds caused by these solder alloys during brazing. To achieve this aim, a new type of multilayer graphene-modified Cu–Sn–Ti composite solder alloy was proposed for brazing diamonds. The brazed diamond specimens were subjected to morphological observation, characterization of the interfacial microstructures. The static compressive strength and impact toughness of brazed diamond grits were measured. The Vickers microhardness of the solidified solder alloy was quantified, and the microstructure of the solidified solder alloy was also analysed. The results show that brazed diamond specimens fabricated with the No. 2 composite alloy containing 1 wt% multilayer graphene exhibited the best morphology. Addition of excess multilayer graphene reduced the flow properties of the molten Cu–Sn–Ti composite solder alloy. The dominant phases in the solidified Cu–Sn–Ti solder alloys were α-(Cu), Sn₃Ti₅, and CuSn₃Ti₅. Cu, Sn, and Ti were adsorbed by the multilayer graphene, forming C-rich and TiC-dominant phases. Consequently, erosion of the diamonds was reduced during brazing, and TiC was formed in the solidified solder alloy. Thus, increasing the content of multilayer graphene enhanced the static compressive strength and impact toughness of the brazed diamond grits, and increased the hardness of the solidified Cu–Sn–Ti solder alloy.