Phase Composition, Microstructure, and Wear Properties of Ni/Ni3Si Composites Prepared by Mechanical Alloying

Ni3Si and Ni/Ni3Si composites were prepared by mechanical alloying with Ni and Si powders as raw materials. The phase composition, microstructure and wear properties of the Ni3Si and Ni/Ni3Si composites were investigated. The results showed that the Ni (Si) solid solution, Ni74Si26 and Ni31Si12 intermediate phases were formed during ball milling process and then Ni3Si nanocrystalline powder was produced after 30 h of milling. Based on Miedema's semi-empirical theory, the formation free energies of different phases formed during mechanical alloying of 3Ni-Si mixed powders were calculated. The results showed that the ordered phase of Ni3Si is stable under equilibrium conditions and has the lowest formation enthalpy during ball milling. Compared with the monolithic Ni3Si, the Ni/Ni3Si composite has an excellent friction and wear resistance and comprehensive strength and toughness. With the increase of load, the friction coefficient of the composite decreases, the wear rate of the composite increases first and then decreases. When the load is 10 N, the friction coefficient and wear rate of the Ni/Ni3Si composite are 0.246 and 5.23 x 10(-4) mm(3)/(Nm), respectively. The main wear mechanism of the material experiences a transition from adhesive wear to abrasive wear with the increase of load, and exhibits a significant tribo-oxidation wear under all loads.