Research On Properties Of CuSnTi-xGa Filler Metals And Mechanism Of Brazing Diamond

At present,there are still some problems in the field of diamond tool cutting.For example,CuSnTi solder used for brazing has low wettability to diamond,which leads to that solder can well wettability diamond,which is not conducive to diamond welding;In addition,the hardness and strength of the solder are low,leading to poor wear resistance of the solder,and easy to cause the reduction of the bonding strength between the solder and diamond in grinding process.At present,there are few studies on the properties of composite low melting point and high strength solder alloys and the service properties of brazed diamond joints.Therefore,in this paper,CuSnTi-x Ga（x=0 wt.%,1 wt.%,2 wt.%,3 wt.%）composite solders with different composition ratio were prepared by adding low melting point Ga element into CuSnTi solder,and the key scientific problems in brazing diamond with optimized performance of composite solders were discussed.Firstly,99.9 wt.%Ga was added to CuSnTi solder and pulse-gravity arc melting was used to prepare composite solder alloys with different composition ratios.The results show that when the Ga content is 1 wt.%,the microstructure of the filler metal is uniform,without obvious defects,and the microstructure of the filler metal is uniform and fine.The shear strength of composite filler metal increases firstly and then decreases with the increase of Ga content.Combined with the fracture morphology,it can be found that when Ga content is 1wt.%,the fracture morphology is typical ductile fracture,and the fracture morphology is fine and dense dimple.Secondly,thermodynamic analysis shows that with the increasing of Ga content,the melting temperature range of the solder decreases,accelerating the transition from solid to molten state of the solder alloy,and the melting point of the composite solder alloy decreases to a certain extent.The melting point of the solder alloy with 3 wt.%Ga content decreases to 123.66℃.The maximum value was 27878.2 J/mol at 1 wt.%Ga.The wetting test results show that the wetting Angle of CuSnTi alloy solder is34.6°when Ga content is 0 wt.%and 29.4°when Ga content is 1 wt.%,while the wetting Angle of CuSnTi alloy solder without Ga is 34.6°.Finally,1 wt.%Ga composite filler metal was added to braze diamond,and the optimum brazing temperature was obtained to prepare brazed diamond tool.The results show that when the brazing temperature is 920℃,the climbing of brazing filler metal is inhibited and the edge height of diamond is higher.The thickness of the brazing interface layer is 0.31μm at 920℃.The measurement results of microhardness show that the maximum hardness value at the interface is 310 HV_0.1 at920℃,and the analysis of mechanical properties of diamond tools shows that the mean removal amount of grinding parts reaches the maximum value at 920℃.The effects of different holding time on interface characteristics and mechanical properties were studied at 920℃.The results show that when the holding time is 6min,diamond particles not only have higher exposure height,but also have complete shape without obvious defects.The thickness of interfacial layer between diamond and solder increases gradually with the increase of holding time（0.25μm-0.62μm）.The hardness of the brazing reaction layer is 318HV_0.1 when it is held at 920℃for 6min.By analyzing the friction and wear properties of brazed diamond tool,it is found that the wear amount of diamond tool to the grinding plate reaches the maximum value of216.82mm³ when the holding time is 6min.Through the analysis of diamond wear morphology,it is found that when the holding time is 6min,the diamond fracture occurs on the diamond matrix,which meets the expected strength requirements.To sum up,the optimal brazing diamond joint tool was obtained under the condition that the brazing temperature was 920℃and the holding time was 6min.