Numerical optimisation of electron beam physical vapor deposition coatings for arbitrarily shaped surfaces

Abstract

For the last few decades, methods to improve the engine efficiency and reduce the fuel consumption of jet engines have received increased attention. One of the solutions is to increase the operating temperature in order to increase the exhaust gas temperature, resulting in an increased engine power. However, this approach can be degrading for some engine parts such as turbine blades, which are required to operate in a very hostile environment (at ≈ 90% of their melting point temperature). Thus, an additional treatment must be carried out to protect these parts from corrosion, oxidation and erosion, as well as to maintain the substrate’s mechanical properties which can be modified by the high temperatures to which these parts are exposed. Coating, as the most known protection method, has been used for the last few decades to protect aircraft engine parts. According to Wolfe and Co-workers [1], 75% of all engine components are now coated. The most promising studies show that the thermal barrier coating (TBC) is the best adapted coating system for these high temperature applications. TBC is defined as a fine layer of material (generally ceramic or metallic material or both) directly deposited on the surface of the part In order to create a separation between the substrate and the environment to reduce the effect of the temperature aggression. However, the application of TBCs on surfaces of components presents a challenge in terms of the consistency of the thickness of the layer. This is due to the nature of the processes used to apply these coatings. It has been found that variations in the coating thickness can affect the thermodynamic performance of turbine blades as well as lead to premature damage due to higher thermal gradients in certain sections of the blade. Thus, it is necessary to optimise the thickness distribution of the coating.