Improved surface properties of AZ31 and AZ91 Mg alloys due to electron beam liquid phase surface treatment

Electron beam alloying (EBA) was applied to improve the surface properties of AZ31B and AZ91D magnesium alloys. Three Al-based additives with different Si contents (0, 12, and 30 wt.%) were pre-deposited on the Mg substrates by atmospheric plasma spraying (APS) and cold gas spraying (CGS). Spraying temperatures above (APS) and below (CGS) the melting point of the oxidation-sensitive Al-based sprayed material caused different amounts of oxide in the coatings, resulting in varying layer qualities. EBA layers using the CGS deposition technique are more homogeneous and reached hardness values up to 200 ... 220 HV0.1. Potentiodynamic polarization tests in 0.001 M NaCl solution showed, compared to the base material, a positive shift in corrosion potential up to 400 mV for EBA layers using AlSi30, with a reduction in corrosion current density of more than 3 times compared to the untreated base materials. The coefficient of wear for all EBA layers reached a minimum at an applied load of 25 N and was reduced by 50 % in comparison to the base material. (C) 2015 Published by Elsevier Ltd.