Crack-free high load Vickers indentation of silica glass

The surface of pure silica glass was prepared to be resistant to cracking from application of Vickers indentation loads of up to one kilogram force (1 kgf). Sample preparation, testing environment, and water content of the glass sample were found to be critical in producing crack-free indentations. Sample preparation consisted of a careful polishing and etching to remove the densified surface layer. Indentation was performed under a nitrogen environment which was also necessary to produce crack-free specimens. Water introduced into the silica glass sample mechanically as well as water introduced into the glass during melting or heat-treatment, were found to be detrimental to crack resistance. (C) 2008 Elsevier B.V. All rights reserved.