Determination of optimal holding time for brazing Cu-Sn-Ti/diamond composites

Diamond particles are brazed by CuSnTi active filler metals under vacuum at 1213 K. The impact of different holding times on wettability, interfacial reaction layer characteristics, and wear resistance of CuSnTi/diamond composite has been systematically investigated. The results show that the complete encapsulation of diamond particles can only be observed after holding for 30 min or further. The interfacial reaction layer is composed of TiC, and the change of the reaction layer thickness follows a parabolic growth rate within 30 min, reaching a maximum of 1.73 μm at 30 min and then remaining almost stable thereafter. It is further shown that when the holding time approaches 30 min, the main phase of the metal matrix changes from Cu41Sn11 to Cu3Sn, and the wear resistance of CuSnTi/diamond composite reaches the maximum value. However, further prolonging the holding time results in slight graphitization of the diamond in the sample, which will reduce the wear resistance of the brazed sample. It is recommended that the holding time shall be limited <30 min for optimized bonding strength and grinding capability.