Turkish Air Force Academy, Turkey
Gursev Pirge received his PhD in 2005 from Bogazici University, Istanbul. He currently works in the faculty of the Turkish Air Force Academy as an Associate Professor. He has published many papers in the fields of smart materials and ceramic coating applications. He also reviews papers for various journals and conferences. Currently, he is Deputy Director of the Institute of Aeronautics and Space Technologies in the Turkish Air Force Academy.
It has been an important target to increase the operating temperatures of the turbine engines with the aim of increasing efficiency and thrust and decreasing fuel consumption. A possible increase in the operating temperature makes it necessary and beneficial to use high temperature protective coatings on the hottest sections of turbine engines. Although there are other alternatives, aluminide diffusion coatings are still frequently used and are being applied to the majority of the first-stage turbine blades. The aluminum in the coating oxidizes to form a dense oxide layer, which acts as a stable barrier to oxidation of the base metal. Aluminide coating also provides some protection against hot corrosion and erosion. Pack cementation, which is usually used to deposit aluminide coatings, involves diffusion and the process being carried out at high temperatures for extended periods may lead to fatal degradation of the mechanical properties of the substrate alloy due to microstructural changes. Thermal barrier coatings have also been widely used in high temperature components of aircraft and industrial gas turbine engines. In this study, aluminide and thermal barrier coatings are applied on various nickel-based superalloys and stainless steels. This paper reviews two major types of protective coatings (aluminide coating and thermal barrier coating) on the alloys used in the hot sections of turbine engines and compares the effects of the substrate on the success of the protection. The experiment results showed that the substrate composition may influence the final microstructure of the system.