Study On Preparation And Properties Of The Vitrified Bond Application In Diamond Wheel

Vitrified bond diamond grinding wheels have high strength,high processing efficiency,high machining precision,good shape retention and long service life,which are widely used for grinding and machining materials such as PCD,super alloy,advanced ceramic,crystal and other super hard materials.In this study,in order to decrease sintering temperature and CTE?coefficient of thermal expansion?,improve mechanical strength,the SiO₂-Al₂O₃-B₂O₃-Na₂O system vitrified bonds have been designed and fabricated using the melting and quenching method.The effects of Na₂O and the ratio of Li₂O to ZnO on the structure and properties of vitrified bond and diamond grinding wheel specimens were investigated respectively.High energy ball milling was used to crush the vitrified bond and the influence of time of high energy ball milling on particle size of vitrified bond was investigated as well as the crystalization temperature and bending strength of vitrified bond.The structures and crystal phases of the vitrified bonds were characterized by XRD and FTIR.Moreover,the thermal dilatometer,Vickers hardness tester and electric universal testing maschine were used to test and analyze the CTE,hardness and bending strength of vitrified bond and diamond grinding wheels samples.At the same time,the SEM was used to characterize the microstructures of the vitrified bond sinters and the interface feature between the vitrified bond and diamond.Finally,we took advantage of laser particle size analyzer and SEM to detect the particle size of vitrified bond dealt with high energy ball milling.DSC and XRD were used to analysize the crystalization temperature and the crystal phases appearing at different sintering temperature.And the results shows:?1?From the study about the effect of Na₂O on the properties of vitrified bonds,it is found that: The sintering temperature of SiO₂-Al₂O₃-B₂O₃-Na₂O system vitrified bond decreased with the amount of Na₂O increasing.When the amount of Na₂O reached 12.31 wt.%,the vitrified bond has the lowest sintering temperature.The diamond grinding wheel samples which contained 37.5 vol.% diamond?230-270#?and 62.5 vol.% vitrified bond?contain 9.31 wt.% Na₂O?were sintered at 680 ?,which has highest bending strength?53.5 MPa?.And the CTE of this vitrified bond is 10.3×10-6/?.?2?The sintering temperature of the vitrified bond decreased and the bending strength of the vitrified bond increased with the ratio of Li₂O to ZnO increasing.The diamond grinding wheel samples were sintered at 580 ? using the vitrified bond contained of 4wt.% Li₂O and 1wt.% ZnO,which has highest bending strength,the value reached 66.4 MPa.And the CTE of this vitrified bond is 9.5×10-6/?.?3?The particle size of vitrified bond can be decreased by the.high energy ball milling.It was found that the particle size of vitrified bond can be decreased to 358 nm after milled 75 min by high energy ball milling.The crystalline temperature of fine vitrified bond powder is 50 ? lower than that of initial vitrified bond powder.The crystalline phase is ?-spodumene for the vitrified bond sintered at 850?.The bending strength of sintered vitrified bond is 61.67 MPa,which is about 40% higher than that of specimens made from raw powder.A futher optimization was applied on the bond,and the crystalization temperature is 696 ?,the bending strength reach to 105 MPa,and the bending strength of diamond composite is 76.6 MPa sintered at 750 ?.