Oxidation protection of gamma-titanium aluminide using glass-ceramic coatings

gamma-TiAl intermetallic alloys are presently considered an efficient structural material for advanced turbine blades and aero-engine components due to their various advantages compared to the traditionally used superalloys. However. their poor oxidation resistance at temperatures >750 degrees C severely limits their wider application. The present study dealt with the improvement of oxidation resistance of this alloy by applying impervious glass-ceramic coatings by vitreous enameling technique. Results showed that MgO-SiO2-TiO2 glass-ceramic coating could offer excellent oxidation resistance to gamma-TiAl at 800 degrees C even up to 100 h with negligible weight gain (similar to 0.10 mg/cm(2)) compared to that of the bare alloy (similar to 1.3 mg/cm(2)). The coatings those were belonging from BaO-MgO-SiO2, ZnO-Al2O3-SiO2 and BaO-SiO2 systems also extend appreciable improvement in the oxidation resistance of the alloy at 800 degrees C upto 100 h. At further higher temperature such as at 1000 degrees C, the ABK-13 and ABK-103 glass-ceramic coatings offered significant protection to the alloy up to 25 h of exposure in air with minimum weight gain (similar to 0.34 mg/cm(2)). However, after that the coated layers started to peel off from the alloy surface. (C) 2008 Elsevier B.V. All rights reserved.