Improving the wear resistance of AA 6061 by laser surface alloying with NiTi

To improve the wear resistance of a popular aluminum alloy AA 6061, a 1.5 mm thick hard surface layer consisting of Ni-Al and Ti-Al intermetallic compounds was synthesized on the alloy by laser surface alloying technique. NiTi powder was preplaced on the aluminum alloy substrate and irradiated with a high-power CW Nd:YAG laser in an argon atmosphere. With optimized processing parameters, a modified surface layer free of cracks and pores was formed by reaction synthesis of Al with Ni and Ti. X-ray diffractometry (XRD) confirmed the main phases in the layer to be TiAl3 and Ni3Al. The surface hardness increased from below 100 HV for untreated AA 6061 to more than 350 HV for the laser-treated sample. Accompanying the increase in hardness, the wear resistance of the modified layer reached about 5.5 times that of the substrate. (c) 2007 Elsevier B.V. All rights reserved.