Fabrication of Al5083-(CeO2-TiO2) hybrid surface composite via friction stir processing combined with plasma electrolytic oxidation

Using friction stir process (FSP) followed by plasma electrolytic oxidation (PEO), a surface composite consisting of Al5083 alloy as the base metal and TiO2 and CeO2 particles as reinforcements was produced. During the PEO process, the base metal was coated with an oxide layer containing the reinforcing particles in an electrolytic solution. FSP was then applied to the PEO-coated base metal. The effect of these nano-sized reinforcements either individually or in combined form on the microstructure, surface hardness, wear behavior, and corrosion resistance of the FSPed samples was studied and compared with the base alloy with no reinforcing particles. The FSP was performed with a rotational speed of 1400 rpm, using a cylindrical threaded hardened steel pin. Optical and scanning electron microscope examinations revealed that the reinforcing particles were uniformly distributed inside the nugget zone (NZ). The PEO and FSP processes resulted in distribution of reinforcing particles, microstructural modification, and considerable improvement in mechanical properties and corrosion resistance of the base alloy. The results showed that the 15 minutes plasma electrolytic oxidation of CeO2 particles, resulted in the most improvement in hardness, corrosion resistance and wear resistance compared to other processing conditions. The corrosion behavior of the samples was evaluated by potentiodynamic polarization tests in a standard 3.5 wt. % NaCl solution. The study was aimed to fabricate surface composites with improved wear behavior and corrosion resistance simultaneously.