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 TiSi2 and Ti5Si3 and TiAl0.3Si1.7 phases and the third layer containing Al2Ti, Al11Ti5 and TiSi2 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.