Soda Lime Silicate Glass-to-Titanium Joining by Controlled Heat Treatments in Air

Glass-to-metal joining is important for improving efficiencies of heat collecting units, employed in parabolic solar collecting systems. In this study, soda lime silicate glass was joined to titanium in air at 700, 800 and 900°C for 5 min by controlled heat treatments. Glass-to-titanium bonding was good and no delamination or macro cracking in glass was observed. During heat treatment, titanium is oxidized in air prior to the reaction with glass. The reaction between oxidized titanium and glass results in bubble formation at joining interface. Bubble formation was found to be decreased with decreasing joining temperature. Thermal stresses developed at glass-titanium junction were modeled by employing ANSYS 14 multiphysics simulation software. For the studied sample profile, soda lime silicate glass, close to the joining interface, experienced rather low residual stresses of the order of 10 MPa maximum and -40 MPa minimum principal stress levels. Good glass-to-titanium bonding and low thermal residual stress are mainly due to similar thermal expansion coefficients of these materials, which was found to be important for achieving successful joining in air.