Laser Melting Effects on Corrosion Behaviour and Wear Resistance of Nano-Structured Plasma Electrolytic Oxidation Coatings

1190 aluminium alloy was treated using duplex techniques of plasma electrolytic oxidation (PEO) and lasersurface melting (LSM). In order to increase the strength and hardness of coatings and to improve the mechanicalproperties, nano-powders are added into the electrolyte during the PEO process.The microstructural characterization andcomposition of PEO coatings and hybrid (PEO – LSM) coatings were characterized by scanning electron microscopy(SEM) and X-ray diffraction (XRD). Additionally, corrosion behaviour and wear resistance of PEO coatings and hybridcoatings were examined by electrochemical corrosion tests (the polarization test in a solution of NaCl 3.5%) and weartest (pin on disk (ASTM-G89 standard)), respectively. Results show that by an increase in the voltage of laser beam,number and size of surface porosities decreases while the number and size of cracks increases, furthermore in some casesfractures are observed on the surface. Results indicate that due to formation of a hard phase produced by surface meltingafter laser treatment, wear resistance of 1190 aluminium alloy is improved. While the hybrid (PEO – LSM) coatingsexhibit higher general corrosion resistance than the one of PEO coatings, their pitting corrosion resistance is lower thanthe one of PEO coatings

Keywords:

Aluminium alloy , Corrosion resistance , Wear resistance , Laser surface melting , Plasma electrolytic oxidation