Surface damage resistance and yielding of chemically strengthened silicate glasses: From normal indentation to scratch loading
in: Journal of the American Ceramic Society (2021)
We report on surface elasticity, plastic deformation and crack initiation of chemically strengthened soda- lime silicate and sodium aluminosilicate glasses during lateral indentation and scratch testing. Instrumented indentation using a normal indenter set- up corroborated previous findings on the effects of chemical strengthening on surface Young ' s modulus, hardness, and indentation cracking. Using lateral indentation in the elastic- plastic regime, we find a pronounced increase in the scratch hardness as a result of chemical strengthening, manifest in higher work of deformation required for creating the scratch groove. Thereby, the glass composition is found to play a stronger role than the absolute magnitude of surface compressive stress. Using a blunt conical stylus for instrumented scratch testing reveals three distinct modes of scratch- induced surface fracture, which occur during scratching or after unloading. Occasional micro- cracking caused by pre- existing surface flaws at low scratching load can be completely suppressed through chemical strengthening. The intrinsic defect resistance to microcracking is reduced as a result of ion stuffing, depending on the initial glass composition, whereas the resistance to abrasive yielding is enhanced by several hundred MPa.