Oxidation of TBC Coated Nickel Based Superalloys and Gamma Titanium Aluminides for Land-Based Engines

Abstract

Our ability to power modern airplanes and land based engines depends largely on the thrust generated most importantly by aero engines. Over the past 30 years material cost has become an important factor, especially in commercial aero engines where light weight and high temperature materials are needed for improved efficiency and specific thrust. The required combinations of high temperature properties has led to the applications of nickel-based superalloys and most recently gamma based titanium aluminides in gas sections of aeroengine. This thesis examines the high temperature oxidation behavior of nickel based alloys and gamma titanium aluminides with thermal barrier coatings. The kinetics of oxidation of the coated structures has been studied at various temperatures (800, 900, 10000C) that are relevant to gas turbine engines. In this study, the effects of oxidation on the stress intensity factor (mode I and mode II cracks) and the energy release rate are computationally simulated using the ABAQUSTM software. Results are discussed in relation to the principal strain in the top coat/TGO interface. The implications of the results are discussed for the design of improved land-based engines and aero-engines.