Title: Effect of Na2SiF6 concentration on the plasma electrolytic oxidation of AZ31B magnesium alloy
Authors: Zeeshan Ur Rehman; Byung Hyun Ahn; Jung Il Song; Bon Heun Koo
Addresses: School of Materials Science and Engineering, Changwon National University, Changwon 641-773, Korea ' School of Materials Science and Engineering, Changwon National University, Changwon 641-773, Korea ' Department of Mechanical Engineering, Changwon National University, Changwon 641-773, Korea ' School of Materials Science and Engineering, Changwon National University, Changwon 641-773, Korea
Abstract: The effect of Na2SiF6 on the composition, morphology and mechanical properties of plasma electrolytic oxidation (PEO) coatings produced on AZ31B magnesium alloy was investigated. It was explored that the addition of Na2SiF6 into the Na2SiO3-NaOH electrolyte solution substantially enhances the surface quality of the PEO coating by eliminating the amorphous residuals and decreasing the surface porosity. Furthermore, the average coating thickness was significantly increased by increasing the Na2SiF6 concentration up to 0.5 g/l with the highest value of coating thickness being 85.31 µm. In addition, hardness was remarkably enhanced, by increasing the concentration of Na2SiF6 up to 0.5 g/l. The X-ray diffractometer (XRD) results revealed that the intensity of MgF2 peaks increases with Na2SiF6 concentration. Major phases detected in the XRD pattern were MgO (periclase), Mg2SiO4 (forsterite) and MgF2. Finally, it was revealed from the wear analysis that the anti-wear resistance of the coatings was significantly improved with Na2SiF6 concentration.
Keywords: AZ31B magnesium alloys; plasma electrolytic oxidation; PEO coatings; fluoride ion; scanning electron microscopy; SEM; sodium fluorosilicate; Na2SiF6; amorphous residuals; surface porosity; coating thickness; wear resistance.
International Journal of Surface Science and Engineering, 2016 Vol.10 No.5, pp.456 - 467
Received: 20 May 2015
Accepted: 07 Sep 2015
Published online: 10 Sep 2016 *