Abstract
Lightweight gamma titanium aluminide (γ-TiAl) intermetallic alloys have recently found application in low-pressure turbine blades in the aviation industry, but their use is currently limited to around 700 °C due to oxidation. This study evaluates the potential of various multilayer coating systems to increase the operating temperature range of γ-TiAl. The coating systems tested are based on a CoNiCrAlY topcoat for oxidation protection and a YSZ diffusion barrier, both applied by atmospheric plasma spraying using a three-cathode torch. Two bond coats, NiCrBSi and CoNiCrAlY, were also tested. Test specimens with bond coats withstood 1000 h of exposure at 900 °C without delamination and no detectable oxygen at the coating-substrate interface. Samples produced with varying feed rates showed that graded coatings can be achieved using the APS process.