Adhesion Tensile Testing of Environmentally Exposed Ti-6Al-4V Adherends

Abstract The structural and bonding properties of Ti-6Al-4V adherends, prepared by chromic acid anodization (CAA), were studied as a function of exposure in high-temperature environments such as vacuum, air, boiling and pressurized water, and steam. Subsequent to the environmental exposure, bonds were produced and the adhesive tensile strengths measured. Long-term exposure to high temperature, dry environments did not cause structural changes to the adherend oxide but did result in poor bond strength. The failure mode in these cases was within the oxide, which was apparently weakened by the exposure. The water-and steam-exposed oxides underwent a transition from amorphous to crystalline TiO2 (with an accompanying change in oxide morphology); however, bond strength was maintained for moderate exposures at T ≤ 250°C. For exposure at T = 300°C, the bond strength was degraded severely. The latter result can be explained by a lack of porosity in the transformed oxide. SEM and XPS measurements were made on debo...