Tribological behavior of BK7 optical glass at elevated temperatures

Aspherical lenses are produced using glass molding technology in a temperature close to its glass transition temperature. Friction and wear between the moving mold surface and the heated glass is one of the important aspects of the optical lenses production. This paper presents an experimental study on the tribological behavior of BK7 optical glass at elevated temperatures using pin-on-disk test rig. Thirty experiments have been conducted to study the effect of operating temperature, applied load, and sliding speed on the friction coefficient and wear rate of BK7 optical glass disks in contact with alumina pin. Also, the relation between the generated entropy and the weight loss under different operating conditions has been studied. The experimental results show that with increasing the temperature up to the glass transition temperature, the wear volume and friction coefficient increase. Further increase in the temperature results in a decrease in the wear volume and friction coefficient. Increasing the applied load results in an increase in the wear rate. An investigation on the correlation of wear rate and the dissipated power shows a linear relation between these two parameters.