Research on the Crack Damage Formation Mechanisms of Polycrystalline Silicon Carbide Ceramics in Grinding Process

doi:10.3901/JME.2022.13.307

Abstract

Abstract: The previous studies on the crack damage formation mechanism of the brittle materials grinding are mainly based on the classical indentation fracture mechanics. However, due to the microstructural heterogeneity of ceramics, the typical cracks generated in the ground surface/subsurface of SiC ceramics are not in accordance with the median/radial cracks system produced in the indentation process, the indentation fracture mechanics may not be valid for the analysis of the crack initiation and propagation during grinding SiC ceramics. Hence, the present research mainly focuses on the crack damage formation mechanism of SiC ceramics grinding from the microstructure perspective. A single diamond grinding method with axial feeding was applied on sintered silicon carbide (SSiC) to explore the role of microstructure on the crack damage formation mechanism. A scanning electron microscope and a transmission electron microscope were used to examine the surface and subsurface morphologies of the grinding groove, respectively. It is found that the propagation of semi-trangranular cracks has preferred direction, and the grain boundaries have distinct induction on the crack initiation and evident obstruction on the crack propagation. The grain boundary crack system is proposed on the subsurface of the ground SSiC, which was caused by the dislocation pileups at grain boundaries. As grinding proceeds, the trans-scale evolution of the grain boundary crack system experiences five stages:dislocation activating, dislocation moving to grain boundary and piling up, microcrack initiating at grain boundary, microcracks propagating and merging into macro intergranular crack and transgranular crack at grain boundary, intergranular crack and transgranular crack propagating to ground surface forming fractured pit. Based on the dislocations pile-up theory, a general fracture mechanics model of the grain boundary cracks system was built, and the critical conditions of the cracks initiation and propagation were analyzed. Finally, an FE model of single diamond grinding polycrystalline SiC ceramics is built to verify the grain boundary cracks system model.

Key words: silicon carbide ceramics, subsurface crack damage, microstructure, grain boundaries cracks system

CLC Number:

TG580

DAI Jianbo, SU Honghua, WANG Zhongbin, DING Wenfeng, FU Yucan, CHEN Jiajia. Research on the Crack Damage Formation Mechanisms of Polycrystalline Silicon Carbide Ceramics in Grinding Process[J]. Journal of Mechanical Engineering, 2022, 58(13): 307-320.

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