Indentation fracture of 4H-SiC single crystal

Understanding the deformation and fracture behavior of single crystal silicon carbide (SiC) under a single particle is of scientific and practical importance for the micromachining of single crystal SiC. In this work, we investigate the indentation fracture of a 4H-SiC single crystal wafer with the indentation direction perpendicular to (0001) plane, using Berkovich, Vickers, and Knoop indenters. All the indentations create radial cracks for the normal loads used in this work. Both the Vickers and Knoop hardness tests produce lateral cracks. The fracture toughness calculated from the Vickers hardness tests is smaller than the ones calculated from the Knoop hardness tests and the Berkovich indentations under large indentation loads. The fracture toughness of 4H-SiC single crystal decreases with the increase of the indentation load under small indentation loads for the Berkovich indentations, revealing the phenomenon of surface hardening. The surface energy calculated from the radial cracks is comparable to the results reported in the literature. We establish an analytical expression of the total energy dissipation of a single indentation cycle, including the contribution of indentation-induced cracking, which offers an approach to calculate the ratio of the energy dissipation due to cracking to the energy dissipation due to plastic deformation and determine the dominant deformation process controlling the indentation deformation. The analysis of the energy dissipation for the indentations of the 4H-SiC single crystal by the Berkovich indenter reveals that the energy dissipation from the indentation-induced cracking is significantly larger than (more than eight times) that from plastic deformation for the indentation loads larger than 75 mN.