Nano-mechanical properties of zirconia-alumina-benzotriazole nano-composite coating deposited on Al2024 by the sol-gel method

Abstract

Nano-composite coatings containing inhibitors can provide protection against corrosion and owing to the favorable hardness and wear resistance, ceramic-based nano-composite coatings such as zirconia–alumina can effectively improve the wear behavior of aluminum. However, defects such as holes, pores, and micro-cracks reduce the protection efficiency and the use of inhibitors can prevent or reduce the formation of defects in the coating. In this work, a zirconia-alumina-benzotriazole coating is deposited on Al 2024-T6 by the sol-gel method with the following precursors: zirconium isopropoxide, aluminum tri-sec-butylate, and benzotriazole. The phase, structure, and morphology of the coatings are studied and the nano-mechanical properties are assessed by nano-indentation and nano-scratch tests under loads of 50 and 60μN. The results reveal the formation of a 810 nm thick homogenous and uniform coating in the presence of alumina and a 945 nm thick crack-free coating in the presence of benzotriazole. Alumina increases the hardness and elastic modulus to 1.15 and 15 GPa, respectively, and abrasive wear is dominated by the shear mechanism and benzotriazole enhances the flexibility and decreases the hardness of the coating.