Friction and wear characteristics of Mg–11Y–2·5Zn magnesium alloy treated by laser surface melting

Abstract

An attempt has been made to enhance the tribological properties of Mg–11Y–2·5Zn alloy by laser surface melting with a 6 kW continuous wave CO₂ laser processing system. The microstructure and microhardness of the surface layer on Mg–11Y–2·5Zn alloy were characterised using X-ray diffractometer, laser microscopy and Vickers hardness indentation. The laser surface melted zone consisted of fine dendrites and coarse dendrites growing epitaxially from the liquid/solid interface. Microhardness was improved from 69–70 HV for the substrate to 77–83 HV for the fine dendritic microstructure. The friction and wear characteristics were investigated using a pin on disc apparatus. The coefficient of friction curve of the laser surface melted specimen was similar to that of the untreated specimen. Laser surface melted Mg–11Y–2·5Zn alloy exhibited good wear resistance, which has been explained by refinement of microstructure in the melted zone. Four wear mechanisms including abrasion, delamination, thermal softening and melting, have been observed.