Fundamental Research On Metal Bonded Diamond Tools With Pre-Brazed Diamond Abrasive Grits

With the development of science and technology and the progress of the society,the application of sintered diamond tools is becoming more and more extensive.However,the most important factor of influencing the service life of the tools is the weak bonding strength of diamond grits to the matrix.In order to improve the bonding strength of diamond grits to the matrix,a new method of surface metallization of diamonds through brazing,i.e.,the pre-brazing process of diamond,is put forward in this paper.The pre-brazed diamonds and diamond tools with the pre-brazed diamonds are fabricated.The main creative concepts are summarized as follows:(1)The pre-brazing process of diamond is developed.The pre-brazed diamonds using Ni–Cr composite brazing filler metal,which consist of Ni–Cr alloy and Cu–Ce alloy,are fabricated.The prebrazed diamonds using Cu–Sn–Ti brazing filler metal are also fabricated.The static compressive strength of the pre-brazed diamonds is measured.The losses of the mechanical strength of the two kinds of pre-brazed diamonds are 12% and 4.6%,respectively.The pre-brazed diamonds all meet the use requirements.(2)The optimal range of weight content of the Ni–Cr alloy in Ni–Cr composite brazing filler metal is 30%~35%.The interfacial microstructures of the pre-brazed diamonds and the pre-brazed diamond segments,and the segment fracture surface were characterized using scanning electron microscope(SEM)coupled with energy-dispersive X-ray spectrometry(EDS)and XRD(XD-3 A X-ray diffraction).The results show that the chemical combination between diamond and Ni–Cr composite brazing filler metal is developed.The interfacial adhesion strength of the pre-brazed diamond segments is higher than that of the conventional diamond segments.(3)The average weight gain coefficient of the pre-brazed diamonds is less than 6.4%.The interfacial microstructures of the pre-brazed diamonds and the pre-brazed diamond segments,and the segment fracture surface were characterized using scanning electron microscope(SEM)coupled with energy-dispersive X-ray spectrometry(EDS)and XRD(XD-3 A X-ray diffraction).The results show that the chemical combination between diamond and Cu–Sn–Ti brazing filler metal is developed.The interfacial adhesion strength of the pre-brazed diamond segments is higher than that of the conventional diamond segments.(4)The impacts disciplinarian of different diamond geometry,diamond volume concentration,carbide thickness,and the pre-brazed metal layer proportion on the stress distribution and mechanical properties of the pre-brazed diamond segments are researched by ANSYS finite element simulation method.The simulation results are in good agreement with the experimental results.(5)Grinding wheels with the pre-brazed diamonds are fabricated.The maching experiments are carried out among the grinding wheels with the un-pre-brazed diamonds,the grinding wheels with the pre-brazed diamonds using Ni–Cr composite brazing alloy,and the grinding wheels with the pre-brazed diamonds using Cu–Sn–Ti brazing alloy.The results show that the processing performance of the grinding wheels with the pre-brazed diamonds using Ni–Cr composite brazing alloy is best when 35 wt.% or 30 wt.% Ni–Cr alloy is used in Ni–Cr composite brazing alloy.The processing performance of the grinding wheels with the pre-brazed diamonds using Cu–Sn–Ti brazing alloy is best when the average weight gain coefficient of the pre-brazed diamonds is 6.4%.The processing performance of the two kinds of grinding wheels with the pre-brazed diamonds is both better than the grinding wheels with the un-pre-brazed diamonds.