Microstructures and properties of TiCp/Al coating synthesized on Ti–6Al–4V alloy substrate using mechanical alloying method

Abstract

A TiCp/Al coating was synthesized on the Ti–6Al–4V alloy substrate by mechanical alloying method. The microstructure, the mircohardeness, the friction and wear resistance and the high-temperature oxidation resistance of the coating, as well as the effect of annealing treatment on them were investigated. The results showed that the coating had a TiC particles reinforced Al matrix composite structure in which the reinforcing particles were uniformly dispersed in the matrix. The microhardness, the wear resistance and the oxidation resistance were improved because of the as-synthesized coating. After annealing treatment, the coating formed a bi-layer structure, including an outer TiCp/Al composite layer and an inner Al3Ti layer. The outer layer had low microhardness and tended to be flaked in both friction and oxidation processes. The inner layer showed more than 5 times of microhardness values of the outer layer and had favorable wear resistance. But during long-time oxidation process, the inner layer had a stronger tendency of forming microdefects compared with the unannealed coating. In general, the TiCp/Al composite coating could protect the substrate from being severe worn or oxidized. The annealing treatment to the coating was conductive to the further improvement of its microhardness and wear resistance, but had limited effects on its oxidation resistance.