Laser cladding of a Mg based Mg-Gd-Y-Zr alloy with Al-Si powders

In the present work, a Mg based Mg-Gd-Y-Zr alloy was subjected to laser cladding with Al-Si powders at different laser scanning speeds in order to improve its surface properties. It is observed that the laser clad layer mainly contains Mg-2 Si, Mg17Al12 and Al-2( Gd,Y) phases distributed in the Mg matrix. The depth of the laser clad layer increases with decreasing the scanning speed. The clad layer has graded microstructures and compositions. Both the volume fraction and size of Mg2Si, Mgi(7)Al(12) and Al-2(Gd,Y) phases decreases with the increasing depth. Due to the formation of these hardening phases, the hardness of clad layer reached a maximum value of HV440 when the laser scanning speed is 2 mm/s, more than 5 times of the substrate (HV75). Besides, the corrosion properties of the untreated and laser treated samples were all measured in a NaCl (3.5 wt.%) aqueous solution. The corrosion potential was increased from -1.77 V for the untreated alloy to -1.13 V for the laser clad alloy with scanning rate of 2 mm/s, while the corrosion current density was reduced from 2.10 x 10(-5)A cm(-2) to 1.64 x 10(-6) A cm(-2). The results show that laser cladding is an efficient method to improve surface properties of Mg-Rare earth alloys. (C) 2016 Elsevier B.V. All rights reserved.