The Si influence on the microstructure and oxidation resistance of Ti-Al slurry coatings on Ti-48Al-2Cr-2Nb alloy

Abstract In the presented study, different Ti-Al-Si coatings were deposited on Ti-48Al-2Cr-2Nb (at. %) alloy via the slurry method. Al and Si's nominal content in coatings was varied (100 at. % Al, Al-5Si, Al-12.5 Si, Al-20Si, Al-40Si, Al-60Si, Al80Si, 100 at. % Si) to find an optimal coating resistant to high-temperature oxidation. The deposited materials were analyzed because of the microstructure and phase composition. Afterwards, the obtained modified aluminide coatings were subjected to the isothermal oxidation at 900 °C for 500 hours. After the oxidation experiment, the oxidized coatings were evaluated, taking into account the microstructure, chemical and phase composition of the oxidation products. The most favourable oxidation behaviour was noticed for the aluminide coatings with Si's small content (respectively 5 and 12.5 at.% Si). In these cases, on the surfaces, the protective α-alumina scale was formed. Moreover, the Ti5Si3 phase was detected for the oxidized Al-12.5Si (at. %) coating. In the case of other coatings, the formation of TiO2 oxide on the surface was observed.