In-process Electrolytic Dressing Lapping (IEDL) of Al2O3-BN Machinable Ceramics

초록

Al2O3-BN ceramic composites with varied BN content were fabricated to make machinable ceramics, which could be easily machined to high precision parts. Al2O3-BN composites are expected to have relatively high strength, high temperature stability and chemical inertness, which may be good for applications in many machine parts. For successful applications of these ceramic composites, machinability can be an important factor, and ultra-precision surface quality, extremely fine surface roughness and minimum surface damage are frequently required.Metal-bonded super-abrasive diamond lapping wheels have superior qualities such as high bond strength, stability and machinability. However, one major problem, encountered frequently, is wheel overloading and glazing, which impedes the effectiveness of the cast-iron bonded diamond lapping wheel. To overcome these shortcomings, the In-process Electrolytic Dressing Lapping(IEDL) process has been developed recently. It can be an effective method to have continuously protruding abrasives on the wheel surface during lapping and to prevent the overloading and glazing phenomena. Therefore, we investigated IEDL of Al2O3-BN ceramic composites to examine the machinability of these composites. The BN contents in the composites and rotating speed and process time of lapping were the main variables in the IEDL process. The increasing rotating speed and process time of lapping tended to improve the surface roughness of the composites after lapping. Higher BN content decreased the hardness of the composites and probably creating many short cracks during lapping, and the composites could be machined more easily. However, higher BN content in the composites resulted in worse surface roughness in general. The relationship between the IEDL process and mechanical characteristics of Al2O3-BN composites obtained in this study could provide useful information to understand the machinability of these unique machinable ceramic materials.