Surface treatment of Invar to improve interfacial adhesion of Invar/Glass Adhesive Joints

Adhesive bonding is extensively utilized in precision optomechanical assembly due to its uniform stress distribution and lightweighting advantages. However, bonding dissimilar materials such as optical glass to metallic supports faces challenges including interfacial stress-induced surface distortion and inadequate bonding strength. This study investigated the effect of physical and chemical surface treatments on the bonding strength of Invar/glass adhesive joints. It was found that sandblasting treatment increased the roughness and led to the biggest bonding strength compared with sandpaper polishing. Among anodization treatments, HCl and NH₄F electrolytes yielded optimal performance. The mechanism was further investigated. Mechanical grinding creates regular grooves and irregular topographies on Invar surfaces, while anodic oxidation generates micro-nanoscale pores. These hierarchical structures facilitate mechanical interlocking during epoxy curing, significantly enhancing interfacial bonding. This research provides an effective surface modification solution for precision optomechanical assembly.