Preparation And Properties Of Brazed Diamond Tools

This paper aims at the problems of low interface bonding strength,easy falling off of diamond and short service life of sintered and electroplated metal bonded diamond tools.Using Ni-Cr-P and Cu-Sn-Ti as matrix materials,diamond tools are prepared by brazing（fusion welding）method to improve the wettability of metal matrix to diamond and realize the metallurgical combination between them,so as to improve the service life and grinding performance of metal bonded diamond tools.The conclusions are as follows:（1）During high-temperature brazing,Ni-Cr-P metal has good fluidity and strong thermal erosion on diamond.C element on the surface of diamond will diffuse into liquid alloy.Cr in Ni-Cr-P metal will react with C to form Cr₃C₂ and prismatic Cr₇C₃,which effectively improves the wettability of gold to diamond.The optimum brazing temperature of Ni-Cr-P metal is 940℃and the holding time is 30min.At this time,the comprehensive performance of Ni-Cr-P brazed diamond abrasive tool is good,and the Rockwell hardness reaches the maximum value of 70.8HRB;After grinding,the surface roughness of the workpiece is 0.99μm.The diamond on the surface of the grinding head is complete and does not fall off in a large area.（2）After brazing at 930℃for 30min,the Ti element at the Cu-Sn-Ti/diamond interface is enriched greatly,and the Wt%of Ti element reaches 53.84%,which reacts with the C element on the diamond surface to form a new phase Ti C.The coverage area of Ti C on the diamond surface can reach 100%,making the diamond surface metallic.The cutting force of Cu-Sn-Ti diamond grinding head is 9s/C,the grinding ratio is52.86%,and the working surface roughness Ra=1.22μm.The surface accuracy PV value is 21.20μm。（3）In the brazing process,Ni-Cr-P metal has a high degree of thermal damage to diamond,and there are different degrees of corrosion pits on the diamond surface;In contrast,Cu-Sn-Ti has a low degree of thermal damage to diamond,the influence of diamond thermal stress,and peeling occurs in local areas on the surface.After brazing at 930℃,the compressive strength and impact toughness of diamond single particle are29.99n and 52.86%respectively,which are only 4.94%and 6.65%lower than 840℃.（4）Compared with electroplated diamond grinding head,the grinding efficiency of Ni-Cr-P and Cu-Sn-Ti brazed diamond grinding head is increased by 46.15%and30.77%respectively.The processing quality of Ni-Cr-P brazing abrasive tool is better than that of Cu-Sn-Ti brazing abrasive tool.The surface roughness（Ra）and maximum peak valley value（PV）of the workpiece are 81.15%and 67.59%of that of Cu-Sn-Ti brazing abrasive tool.