Tribological characteristics of an A356 aluminium alloy laser surface alloyed with nickel and Ni-Ti-C

Laser surface alloying of an A356 aluminium alloy was performed in order to improve the tribological behaviour of its surface using nickel and Ni-Ti-C powders to provide a reinformcement of intermetallics and ceramic phases. Alloying with nickel resulted in the formation of Al-Ni intermetallics whilst alloying with Ni-Ti-C led to the formation of Al-Ni and Al-Si-Ti intermetallics together with TiC particles produced by an in-situ reaction within the melt. The surfaces achieved hardness values of up to 3.5 times that of the untreated material, and these values were related to the overall content of alloying elements in the alloyed surface. The sliding wear resistance of surfaces alloyed with nickel and Ni-Ti-C was highly improved when using powder flow rates of more than 0.04 g/s, attaining mass loss due to wear at least 15 times less than that of the untreated material. A reduction of plastic deformation and adhesive wear with increasing alloying addition was the main reason for this improvement.