High Temperature Interfacial Reaction between Glass Gobs and Sol-Gel Coated Al₂O₃ Films

. Glass molding process is considered to have a great potential for the mass production of optical components with lower cost. Up to now, the service life of molding dies is still not satisfied. This study mainly focuses on the development of sol-gel derived Al2O3 coatings in order to extend the service life of glass molding dies. High temperature glass wetting experiment was carried out to investigate the high temperature interfacial reaction between the coatings and glass gobs. The 304 stainless steel were used as the substrate materials. The sol-gel coated Al2O3 was selected as the protective coating. OHARA L-BAL42 glass gobs were chosen as the test materials. It can be observed that very severe interfacial reaction occurs between stainless steel and glass at high temperature. The contact angle dramatically decreases from initial and then gradually approaches 25° at 825°C after 2 minutes holding time. The severe interface chemical reaction also results in the loss of transparency in glass appearance. The reaction products such as Zn and Ba are mainly from glass material. For the case of Al2O3 coated substrate, the variation of the contact angles varied from 152 to 138°, presents anti-sticking or non wetting behavior. There are no reaction products can be found on the glass contacted area after wetting test.