Study On Preparation Technology And Grinding Mechanism Of Vitrified Grinding Wheels With D-M0.5/1.5 μM Diamond

Ultra-precision grinding,also known as micro-grinding,is a precision manufacturing process used in various fields.It is a grinding process that removes materials to obtain a specific surface shape.Ultra-precision grinding is often used to achieve the plane parallelism,perpendicularity,centering and contour of hard and brittle materials and micro parts,so ultra-precision grinding is often used as the final processing procedure.Vitrified diamond grinding wheels with good heat resistance,and acid and alkali resistance own important application value and broad prospect in processing functional ceramics,cemented carbide and refractory stone processing.The finer granularity of abrasives used in grinding wheel,the lower surface roughness of the workpiece after grinding and the smaller the subsurface damager layer.At present,the preparation of vitrified diamond with size greater than 10μm grinding wheel has become perfected.However,as the abrasive size is less than 10μm,the preparation of the grinding wheel has not been properly developed and design for size effect.D-M0.5/1.5μm diamond（referred to as M0.5/1.5 diamond）is agglomerated and difficult to mix uniformly with vitrified bond due to the large specific surface area and high surface energy.It’s difficult to prepare pores with high volume fraction and large size due to the limitation of pore making agent and the debris in the grinding process cannot be fully accommodated.In order to make full used of the advantage of M0.5/1.5diamond and porosity inside the vitrified M0.5/1.5 diamond wheel and analyzes the grinding mechanism of the wheel and workpiece.The main research contents of the paper were as follows:（1）Al₂O₃-SiO₂-B₂O₃-Na₂O vitrified bond was prepared by sol-gel technique.the effects of raw materials,Al（NO₃）₃·9H₂O,Na NO₃,H₃BO₃ and orthosilicic acid tetracthyl ester（TEOS）on the properties of vitrified bond,such as,refractoriness,bending strength and coefficient of thermal expansion were investigated by four factors and three level orthogonal test and single factor variable test.The order of the effects of raw materials on the properties of the bond was compared and the formula was optimized.Scanning electron microscopy（SEM）,x-ray diffractometer（XRD）and infrared spectrometer（FIR）were used to investigate the effect of the addition on the microstructure of vitrified bond.（2）Uniformly dispersed M0.5/1.5 diamond/vitrified bond composites were prepared by sol-gel technique.The effects of anionic surfactant Sodium Dodecyl Benzene Sulfonate（SDBC）,cationic surfactant Hexadecyltrimethylammonium chloride（CTAC）and nonionic surfactant Tween 80 on the dispersion of diamond in vitrified bond and bending strength of composite materials were researched,respectively.Besides,the addition of surfactants was optimized.The results show that compared with CTAC and Tween 80,SDBC dispersed uniformly M0.5/1.5 diamond in vitrified bond.it is necessary to equivalently reduce Na⁺in Na₂O to maintain the bending strength and hardness.（3）The vitrified bond was prepared by melt-quenching technique（VB-MQ）and as raw materials was used to prepared composite vitrified bond and composite vitrified M0.5/1.5 diamond powder by sol-gel technique.What’s more,the microstructure and properties of that were investigated.Besides,the dispersion of M0.5/1.5 diamond in composite vitrified bond was studied.The machining performances including machining efficiency,surface roughness and grinding mechanism of the Pc BN tools with composite vitrified M0.5/1.5 diamond grinding wheel were researched.When the proportion of VB-MQ is 50%and 75%,respectively,M0.5/1.5 diamond are adhered to VB-MQ.When the proportion of VB-MQ is 100%,M0.5/1.5 diamond agglomerates together and is mixed with VB-MQ.When the Pc BN cutters is ground by M0.5/1.5diamond composite grinding wheels with a mass fraction of 50%of VB-MQ,the optimal speed of the wheel is 3000 rpm.（4）The optimized composite vitrified M0.5/1.5 diamond powder was employed to prepare porous and vitrified diamond grinding wheel by foaming method and sapphire grinding tests under fixed load were carried out to study the effect of grinding parameters of the grinding including the grinding wheel spindle,pressure on the sapphire and sapphire spindle speed on surface roughness,depth of subsurface damager layer and surface morphology.Different wear mechanisms play the role as the sapphire is grinding by porous and vitrified diamond grinding wheel,ductile grinding mode and brittle grinding mode.As the above experimental parameters are adopted to precisely grind sapphire,wheel spindle speed below 1200 rpm,pressure on sapphire lower than15 N and sapphire spindle speed below 30 rpm tend to lead the sapphire to be removed by the ductile grinding mode.Conversely,brittle grinding mode and ductile grinding mode are the main removal mechanism of sapphire at other experimental parameters.It is found that grinding wheel spindle speed,pressure on the sapphire and sapphire spindle speed affect the material removal rate of sapphire.The MRR enhance as the above experimental parameters increase.Besides,the effect of experimental parameters on the MRR follows the order:pressure on sapphire>sapphire spindle speed>grinding wheel spindle speed.When the sapphires were polished respectively by porous and vitrified M0.5/1.5 diamond grinding wheels adding PMMA microspheres or vesicant,the results show that the porous and vitrified M0.5/1.5 diamond grinding wheel adding vesicant has better processing performance than that adding PMMA microspheres and molded by cold pressing due to the large pore volume fraction and pore size.