电火花机械复合磨削反应烧结SiC陶瓷的表面特征

研究了基于电火花机械复合磨削技术加工的反应烧结碳化硅(RB-SiC)陶瓷的表面特征。用电火花机械复合磨削(EDDG)、电火花磨削(EDG)以及普通磨削(CG)三种方法加工RB-SiC陶瓷,并采用激光共聚焦显微镜和扫描电子显微镜对加工后的SiC陶瓷的表面粗糙度、表面形貌及微观裂纹进行测量和对比试验,获得了RB-SiC陶瓷的EDDG加工特性。实验显示:EDDG加工的RB-SiC陶瓷的表面粗糙度优于EDG加工的表面粗糙度,为0.214 9μm,但比CG加工的表面粗糙度0.195 6μm略差。对加工后的SiC陶瓷表面形貌观察显示,传统磨削加工后的表面存在明显划痕,EDG加工表面主要由放电凹坑组成,而EDDG加工表面同时存在放电凹坑和磨削划痕;另外,传统磨削表面也存在磨削裂纹和晶界裂纹,但EDG加工后的表面只存在热裂纹,而EDDG加工后的表面存在磨削裂纹和热裂纹,不过热裂纹可以用金刚石磨粒磨削去除。对比实验显示RB-SiC陶瓷的EDDG加工与EDG和CG加工获得了不同的表面特征。

Surface characteristics for RB-SiC ceramics by electrical discharge diamond grinding

The surface characteristics of reaction-bonded SiC (RB-SiC) ceramic with Electrical Discharge Diamond Grinding (EDDG) were explored. Three kinds of processes of EDDG, Electrical Discharge Grinding (EDG) and Conventional Grinding (CG) were taken into the experiments of RB-SiC grinding. Then the surface roughnesses of the RB-SiC were measured with a laser scanning confocal microscope, and their surface morphologies and micro-cracks were observed with a scan electron microscopy. The grinding characteristics of the RB-SiC with EDDG were analyzed and compared to that with other two methods. The results show that the surface roughness value of RB-SiC is 0.214 9 μm with the EDDG, which is better than that with EDG but slightly poorer than 0.1956 μm with the CG. For the surface morphologies of the RB-SiC, it shows obvious discontinuous scratches with the CG, and is mainly composed of discharge craters with the EDG machining. However, both scratches and discharge craters are existed on the machined surface with the EDDG. Moreover,the grinding cracks and grain boundary cracks are found on CG surface and only hot cracks exist on the EDG surface. But the micro-cracks on EDDG surface are divided into grinding cracks and hot cracks, and the latter can be ground with diamond grits. With the investigation of comparative experiments, the results show that different machined surface characteristics of RB-SiC ceramic with EDDG process from that with EDG and CG processes.