EFFECTS OF LASER RADIATION ON THE WETTING AND DIFFUSION CHARACTERISTICS OF KOVAR ALLOY ON BOROSILICATE GLASS

摘要

The purpose of this study was to investigate the advantages of laser surface melting for improving wetting over the traditional approach. For comparison, kovar alloy was preoxidized in atmosphere at 700°C for 10min, and then wetted it with borosilicate glass powder at 1100°C with different holding time in atmosphere. The proposed approach used a Nd:YAG laser to melt the surface of the kovar alloy sample in atmosphere, then wetted with borosilicate glass powder at 1100°C with the same holding time. The laser melted surface shows a decrease in contact angle from 47.5 degrees to 38 degrees after 100 minutes. The diffusion mechanisms were discussed for both approaches. Scanning electron microscope revealed that an iron oxide interlayer in the joint existed under both conditions. Fayalite nucleated on the iron oxide layer alloy and grew into the glass. In both cases, neither Co nor Ni were involved in the chemical bonding during wetting process. The work has shown that laser surface melting can be used to alter the wetting and diffusion characteristics of kovar alloy to borosilicate glass. This work demonstrates that it is possible to alter the wetting characteristics of Kovar alloy using the laser to melted kovar surface in atmosphere to substitute for the traditionsal thermal treatment of kovar.