Microstructures of Sintered Ceramic Bond Silicon Carbide Grinding Wheel
Abstract: Microstructures of sintered ceramic bond has an important effect on the behaviour of the silicon carbide grinding wheel. The paper mainly studied the microstructures of sintered ceramic bond of SiC grinding wheel. The results showed: The bond had the typical sintered state. There were many phase boundaries and microcracks in the bond, the degree of bonding between bond and abrasive grains was not the same in different parts. Some large size pores were found in the bond, and the largest pore was 50 μm in diameter. The energy spectrume analysis and elements plane distribution proved that the phases of the bond were composed of glass and residual quartz particles. Three kinds of microcracks were found in and around the residual quartz particles, the intragranular crack within the residual quartz grains with a relatively straight cracks, the circumferential crack in the close vicinity of a quartz particle in a form of circular arc and the microcrack within the glass around the residual quartz particle. There were obvious microcracks when the size of residual quartz particle was 25 μm. No microcrack was found when the size of the residual quartz particle was less than 10 μm.The relationship between the microstructures of the grinding wheel and their performance was discussed theoretically.
石英原料在烧结结合剂中起了很重要的作用。如果较大颗粒的石英没有熔融完,在结合剂中尚有残留,则在冷却过程中会发生晶型转变,产生体积收缩,并在石英晶体与玻璃相之间因热膨胀系数的失配而产生微裂纹,降低了磨具的机械性能。早先的资料[2]认为,石英粒度约50 μm时容易产生显微裂纹,而当粒度下降为25 μm时,就可减少这种显微裂纹,从而提高坯体的机械强度。M. J. JACKSON[3,4]等人曾对石英在陶瓷坯体中的熔解进行了定量研究,并提出了有效的可以预测石英熔解情况的模型,该模型对使用粘土-长石-石英系统制备烧结结合剂碳化硅陶瓷磨具有很好的指导作用。
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