Modification of tribology and high-temperature behavior of Ti–47Al intermetallic alloy nitrided by N ion implantation

N ion Implantation in Ti–47Al–2Nb–2Cr intermetallic alloy has been investigated for surface-nitriding treatment to modify tribology and high-temperature oxidation properties of the material. The alloy samples were implanted using either normal (medium)-current or high-current N2 ion beams at an energy of 140 keV to doses of 4×1017–4×1018 ions/cm2. Post-annealing was performed to the ion beam-treated samples at temperatures of 200 and 300°C for different periods (24–240 h). The treated samples underwent tests of microhardness, tribology and high-temperature oxidation. The results show that N ion implantation and post-annealing improve surface hardness in all cases, wear resistance in the case of high-current and high-dose ion implantation, and high-temperature oxidation behavior in the early testing stage. N ion implantation particularly with high beam current and high ion dose without post-annealing results in the best modification of tribology. XRD analyses indicate that the formation of metal nitride and oxide is supposed to be responsible for the modification of the relevant properties. Compared to the gas-nitriding technique ion implantation has some advantages and shortcomings.