Effective Machining of Fine Ceramics by Honing: Mechanism of Chip Formation and Machinability of Work Materials

The mechanism of chip formation and the machinability of fine ceramics are investigated by both honing operation and scratching test using a conical diamond tool. The workpieces are alumina Al2O3, silicon nitride Si3N4 and silicon carbide SiC which are sintered under atmospheric pressure, and borosilicate glass (SiO2). Based on the experimental results which were done by the authors, the specification of the diamond sticks is decided to obtain superior honing performance. The results are as follows. The machinability of work materials is best in SiO2 and deteriorates in the order of Al2O3, Si3N4, and SiC. Comparing the shape and size of chips made by honing with the grain structure of Al2O3 and Si3N4, it can be estimated that the chips are mainly formed by the fracture occurred along the grain boundary, although chips of Si3N4 are also formed by the fracture occurred through the grain. Two types of material removal are observed depending on the load acting on the cutting grits. When the load is small, the cutting grits are in the condition of wear and the surface roughness of the work material is improved. When the load is set above the critical value, a lot of chips are created and there remains many large craters on the surface honed.