PVD COATINGS FOR PROTECTION OF AERO ENGINE COMPONENTS UNDER EXTREME ENVIRONMENTS

Abstract

Advanced aero engines operate in military applications under extreme conditions. This ultimately calls for materials with increased high temperature capability and lightweight components that are pushed to its limits. Usage of coatings offers the potential to prolong lifetime, to increase operating temperatures, and to protect turbine components. Several PVD coating techniques that are used to protect turbine parts will be presented. Thermal barrier coatings (TBCs) are applied to increase lifetime and efficiency of turbine blades and vanes in aero-engines and land-based gas turbines by reducing the average metal temperature and mitigating the detrimental effects of hot spots. The presentation highlights the behaviour of coatings that are produced by electron beam-physical vapor deposition (EB-PVD) especially under high loadings of dust, commonly described as calcium-magnesium alumino-silicate (CMAS) deposits, that are ingested in aero-engines during the flight. CMAS particles melt in the combustion zone and are subsequently deposited on hot surfaces of engine components such as combustor walls or high-pressure turbines. The degradation of thermal-barrier coatings by CMAS attack can be lifetime-limiting and will change the properties of the TBC such as thermal conductivity and mechanical behavior. The presentation provides results on several new TBCs, especially their behaviour under the influence of deposits. PVD methods are also capable to protect CFRPs against erosion which is another damaging effect in aero-engines, especially under military operating conditions. Here multilayers of metallic and hard coatings are favoured to effectively protect the underlying material. Finally, for very extreme conditions in terms of temperature that can be present in hypersonic flight applications such as wing leading edges, nozzles of rockets or even in future ramjet engines, Ultra High Temperature Ceramics (UHTCs) are a potential solution. The also show degradation under oxidizing atmosphere that can be lowered by appropriate coatings. The presentation will show first results on promising PVD-based metallic and ceramic coatings.