Sintered Polycrystalline Diamond(PCD)vacuum Brazing Process Foundation And Experimental Research

Polycrystalline diamond(PCD)is widely used in the field of diamond tools due to its excellent properties of high hardness,high thermal conductivity,low thermal expansion coefficient,high elastic modulus and low coefficient of friction.In addition to mechanical clamping and bonding methods,PCD composite plates are mostly pressed on the cemented carbide matrix by brazing.Vacuum brazing has the advantages of accurate temperature control,uniform heating of the brazed sample,small deformation,and mass production.In recent years,it has been more and more widely used in the field of tool processing.In view of the present to the actual of sintered PCD containing variable Co-binder contents vacuum welding process is not clear,and in the welding process of different types of PCD,the basic experimental results of different processes are not understood.PCD without tungsten carbide substrate was selected as the subject in this subject.The research object is to explore the soldering process of sintered PCD containing variable Co-binder contents by adding active Ti element Sn-based solders.The goal is to achieve low-temperature and reliable brazing connections under the premise of reducing thermal damage and reducing stress;at the same time clarify the different Interfacial reaction behavior of binders with cobalt content PCD.Firstly,the wetting performance of three different binders with cobalt content(Co: 8,12,18 wt.%)PCD substrates on Sn-2Ti active solder was investigated by heating and wetting experiments.The initial wetting time was inconsistent.As the Co-binder contents increased,the wetting inflection point was advanced.And during the constant temperature wetting experiment,it was found that the interface products of the PCD substrates with three different cobalt contents at the three-phase line are different.When the cobalt content is low,it is almost impossible to observe the bulk CoSnTi IMCs,and when the cobalt content of the binder increases,a large amount of CoSnTi IMCs can be observed at the wetting triple line,and TiC carbides are nano-shaped at lower temperatures and at higher temperatures Were rod-like.According to the spreading kinetics analysis under constant temperature experiments,it can be known that the that the spreading kinetics of Sn-2Ti active solder on sintered PCD substrates exhibits a chemical reaction-controlled feature at 650-900°C.Based on the previous wetting experiment,the welding process was defined.SnCuTi powder active solder and commercial AgCuInTi powder active solder were selected to prepare the solder joints of 45 steel and different Co-binder PCD substrates.The shear strength and failure mode of the PCD solder joints were characterized and analyzed through the shear strength test under different processes.In the brazing experiment of SnCuTi brazing PCD / 45 steel,with the increase of brazing temperature,the shear strength of the brazed joint is further enhanced,but at the same brazing temperature,as the cobalt content of the binder in the PCD substrate increases,the shear strength value of the brazed joint increases first and then decreases.According to the fracture morphology analysis after the shear test,it can be seen that the PCD substrate has formed a good chemical bond with the solder.and the failure form of the solder joint is mainly the fracture at the reaction layer of filler metal at the welding seam,while the low shear strength of the experimental results is due to the high content of Sn in SnCuTi filler metal.In the brazing experiments of AgCuInTi brazing PCD / 45 steel,with the increase of brazing temperature,the shear strength of brazed joints is further enhanced.And at the brazing temperature of 900~oC,the creeping phenomenon of the brazing material wrapped the PCD substrate at the brazing joint,so that the shear strength value of the brazing joint increased to about 160% of the original PCD substrate.According to the fracture morphology analysis after the shear test,it can be seen that the PCD substrate and the solder have formed a good chemical combination,and the failure form of the solder joint is the fracture of the PCD layer of the original material at the weld.