Influence of amorphous hydrogenated carbon coating on the strength and cracking resistance of a glass in the high-strength state

The strength of sheet glass treated by etching in a hydrofluoric acid with subsequent deposition of an amorphous hydrogenated carbon coating 50 nm thick is investigated. The carbon coating is applied by ion magnetron sputtering of a chemically pure graphite target. It is shown that the strength of the sheet glass after coating is retained at a level of 2.4 GPa. The leaching of the surface glass layer upon treatment in water at a temperature of 96°C prior to the deposition of a coating leads to an increase in the strength by 12%. The cracking resistance of the glass is examined by the microindentation technique. It is revealed that the load P _c which corresponds to the formation of 50% of all the cracks increases by a factor of three upon deposition of the coating and by a factor of 15 after the preliminary leaching of the glass surface. The assumption is made that the preliminary leaching of the glass surface considerably enhances the adhesion of the hydrogenated carbon film to the glass surface and, thus, improves its protective properties.