Microstructure and Wear-Resistance of In-Situ Synthetic Intermetallic Compound Modification Coating Formed on Al Alloy Substrate by Laser Alloying

The surface modification coating composed of Ti-Al and Ni-Al intermetallic compounds was fabricated on 6061Al substrate using a high-power continuous wave Nd-YAG laser, by means of laser surface alloying of NiTi powders as the raw material. The microstructure, surface morphology, composition distribution, hardness profile, and wear-resistance of the surface alloying coating were analyzed using X-ray diffraction, scanning electron microscopy, microhardness measurement, and friction and wear test. It was found that the NiTi powders were successfully alloyed onto the aluminium alloy surface by way of overlapping single track at the optimal process parameters, and the resulting surface alloying coating had good metallurgical bonding with the Al alloy substrate. The surface alloy coating was compact and free of crack, and it was mainly composed of TiAl_3 and Ni_3Al intermetallic compounds dendrites. The hardness of the laser-alloyed surface was 3 to 5 times as much as that of the Al6061 alloy substrate, while its wear-resistance was dramatically increased than the 6061Al substrate.