Synthesis of Ti–Si–Al coatings on the surface of Ti–6Al–4V alloy via hot dip siliconizing route

Abstract Hot dip siliconizing method was proposed as a fast, simple and easy-echo route for synthesis of Ti–Si–Al coatings on the surface of Ti–6Al–4V alloy. Rectangular blocks were dipped into the Al-Si melt at the different melt temperatures and immersion intervals. Results showed that coatings with three sequential layers have been formed on the surface of the bare alloy after coating process; the first layer attached to the substrate composed mainly of TiAl, the second one consisted of TiSi 2 and Ti 5 Si 3 and TiAl 0.3 Si 1.7 phases and the third layer containing Al 2 Ti, Al 11 Ti 5 and TiSi 2 phases. Moreover, the thickness of the Ti-Si intermediate layer increased with increasing process temperature and soaking time. The growth kinetic of the silicide layer follows the Arrhenius' relationship with the activation energy of 100 kJ/mol. Furthermore; the temperature of 850 °C was introduced as the optimum process temperature to obtain a titanium silicide layer with a proper thickness at a desirable immersion time. Finally, it was indicated that the coating process improved the high-temperature oxidation resistance of the Ti–6Al–4V alloy.