Study On Diamond Abrasives For Grinding Porous Ceramic Bond Of Hard And Brittle Materials

With the development of machining and grinding technology,the use of the new generation of abrasive tools for ultra-precision grinding and polishing of semiconductor and other hard and brittle materials,represented by ultra-hard ceramic abrasive tools,has been increasing year by year,and is becoming a new research hotspot.Ceramic grinding wheels with porous structure can effectively solve the problems of poor sharpness,ductility deformation and poor workpiece surface quality in the grinding process of hard and brittle materials.Compared with metal binder and resin binder abrasives,one of the important characteristics of ceramic binder abrasives is that the number and size of pores can be adjusted according to the requirements of use.It has better shape retention performance,easy dressing and higher grinding efficiency.It is an excellent ideal machining tool.The hardness and strength of ceramic bonded grinding wheel are closely related to the structure of pores,so it is of great significance to study how to properly adjust and control the number,size,shape and distribution of holes in grinding tools according to different grinding uses and processes.This paper mainly studies the binder used for porous ceramic grinding tools.First,B₂O₃and two nucleating agents ZrO₂and Ti O₂were used to modify the basic ceramic binder.By adjusting their addition amount and utilizing their respective characteristics,the influence of these agents on the ceramic binder was explored,and a bond with higher strength suitable for porous ceramic grinding tools was prepared.Then,the influence of pore forming agents on the structure and performance of porous ceramic grinding tools was investigated by adding PMMA,Ca CO₃,and their composite pore forming agents.The porosity and flexural strength were controlled by adjusting the relative content of pore forming agents and changing the sintering system.The relationship between the grinding ratio,removal rate,and workpiece surface quality of different components of composite pore forming agent grinding tools for grinding silicon carbide ceramics was studied.The experimental results are as follows:（1）The addition of B₂O₃can greatly improve the performance of ceramic binders,with a fire resistance and flowability of up to 688℃and 150.73%.The performance of both glass samples and ceramic bond powder sintered samples showed significant boron anomalous characteristics.The highest flexural strength of the ceramic bond was 78.11MPa when the molar fraction of B₂O₃was 15%;At the same time,the glass sample has the highest microhardness and density,respectively 856MPa and 2.45g/cm³,and the coefficient of thermal expansion is as low as 5.62×10^-6/℃,close to the coefficient of thermal expansion of diamond,which is conducive to forming an ideal composite structure with diamond,while increasing the wear resistance of the abrasive tools made.（2）ZrSi O₄andα-Si O₂crystal phases were precipitated at 602℃and 677℃after sintering of ceramic binder with ZrO₂.The ceramic binder added with Ti O₂was sintered at584℃and 672℃for each holding for 1h to precipitate traceα-Si O₂crystal phase.When ZrO₂was added,the refractoriness of the ceramic binder reached 764℃,which was 26℃higher than that without ZrO₂,and the fluidity was 19℃lower than that without ZrO₂.The addition of Ti O₂reduced the refractoriness of ceramic binder by 28℃and increased the fluidity by 9.19%.The two kinds of nucleating agents can increase the flexural strength of the ceramic binder,which can reach 86.01MPa and 89.22MPa,respectively.（3）The bending strength of the grinding tools with the mass fraction of 40%diamond,32%white corundum and 28%binder is the highest,reaching 29.58MPa.At 760℃for90min,the bending strength of the spline using 7.5%PMMA and 2.5%Ca CO₃composite pore-making agent reaches 13.03MPa and the porosity is 36.38%,which makes up for the deficiency of a single pore-making agent.XRD diffraction results show that the pore-making agent Ca CO₃in this sintering system completely decomposes the bubble,and the Ca O generated is fully integrated into the glass phase of the ceramic binder and further improves the strength of the grinding tool.（4）The multi-hole grinding tools with compound pore-making agent keep relatively stable friction coefficient during grinding,and the fluctuation range is not large,and the friction coefficient is lower than that of single pore-making agent grinding tools.Compared with non-perforated grinding tools,the grinding ratio of composite perforated grinding tools can be increased by 2 times,and the grinding rate can be increased by nearly 3 times.The surface quality of the grinding workpiece is mainly related to the diamond size,but has little relationship with the porosity.The porosity containing the grinding chips and the intensity of the grinding tools have an effect on the surface scratches.The surface of the workpiece after grinding with the composite pore-making agent abrasive tools is the most flat,and the surface roughness is the lowest,which has a good prospect of industrial application.