Wetting behavior of constructional window glass and Kovar alloy

In order to realize reliable sealing and combination of constructional glass and Kovar alloy, the effects of temperature, holding time, roughness and oxide layers on their wetting property were studied. When the temperature increased from 800℃ to 900℃, the viscosity of liquid glass reduced, so the wetting angle decreased from 69.5° to 31.1°. When the holding time prolonged from 5 min to 40 min at 850℃, the liquid glass had enough time to diffuse under the condition of low viscosity, and the wetting angle increased by 30%. With an increase in roughness of steel sheet surfaces, the barrier increased which was needed to overcome by the liquid glass to spread around. When the roughness value Ra increased from 0.186 μm to 0.563 μm, the wetting angle increased from 46.9° to 69.5°. The oxide layer on the surface of Kovar alloy and the liquid glass had diffusion reaction that could form strong ionic bonds, which increased the wetting property considerably, and the wetting angle could decrease by 23.6%. Therefore, during the actual sealing process, increasing the temperature and holding time, decreasing the roughness of steel sheet surfaces, and steel sheet pretreatment could effectively improve the wetting property of the glass and Kovar alloy.