精密仪表用铝合金瓷质阳极氧化表面粘接性能研究

The porcelain-like anodizing (PLA) process for aluminum alloys is a special and key technology in the manufacture of precision instruments, but the bonding structure with the anodized surfaces often suffers from connection failures such as debonding and leakage. To study this issue, the micro-nano morphology and wettability of the porcelain-like anodized surface and the bonding strength and failure mode at high and low temperatures were examined, comparisons with the naturally oxidized (NO) surface and the phosphoric acid anodized (PAA) surface were carried out, and the influence mechanism of adhesive failure on the precision anodized surface was understood. The results show that although PAA does not significantly change the surface roughness on the micron scale, its anodized film with nano-scale porous structure can improve the surface wettability and the interfacial bonding force; the SEM morphology at 50k times shows that the PLA surface is relatively dense and smooth, which is not conducive to wetting and adsorption of the adhesive; both the temperature (from −30 ℃ to 80 ℃) and the surface factors have significant effects on the bonding strength, and the strength decreases with the increase of the temperature; the bonding strength of the PAA surface is the highest (36.75-20.54 MPa), then the NO surface followed by the PLA surface (24.79-17.10 MPa). The thermal infrared and energy spectrum analyses show that the adhesive strength of the PLA surface is lower than the cohesive strength of the adhesive, and the failure mode is adhesion failure, while the failure mode of the PAA surface is the cohesive failure of the adhesive. Therefore, the adhesion failure of the PLA surface mainly results from the compact anodized film, which is not conducive to adhesive wetting and adsorption and then weakens the mechanical interlocking effect between the adhesive and the substrate surface compared with the PAA film with nano-scale porous structures.