Deformation created by Berkovich and Vickers indenters and its influence on surface morphology of indentations for LiF and CaF2 single crystals

The study of the deformation zone around the indentations made by Berkovich and Vickers methods on LiF and CaF2 single crystals revealed several discrepancies in surface morphology. One of them is the presence of well-pronounced crack formation for Berkovich indentations and a total lack of that for the Vickers ones made at the same load on CaF2 crystals. The investigation of fine surface relief of indentations using atomic force microscopy revealed a faceted relief of the surface of Berkovich indentations as distinct from the smooth surface of the Vickers ones for both LiF and CaF2 crystals. Taking into account the peculiarities of each of the used methods, it was concluded that the geometry of indenters here has a major influence. The calculations showed that the trihedral Berkovich indenter with a smaller apical semi-angle against the tetrahedral Vickers indenter with a bigger semi-angle, on the one hand, and the smaller tip radius of the Berkovich indenter in comparison with the tip radius of the Vickers indenter, on the other hand, are the two factors which cause larger deformation of material under the Berkovich indenter as compared with the Vickers one. This fact leads to specific peculiarities of the deformation process and, as a result, to the appearance of specific surface morphology of indentations.