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This study investigates the microstructural evolution and damage mechanisms of the nickel-based single-crystal superalloy DD9-thermal barrier coating (TBC) system under 1050 °C high-temperature oxidation, while conducting a comparative analysis of oxidation behavior with the DD6-TBC system. Results show that both systems have similar oxidation mechanisms but face long-term oxidation drawbacks: as oxidation time increases, the thermally grown oxide (TGO) evolves into a mixed oxide layer and an Al2O3 layer, with initial rapid TGO growth consuming Al in the bond coat (BC) and subsequent Al depletion slowing growth, though long-term TGO accumulation raises cracking and spallation risks. DD9 and DD6 substrates significantly affect substrate-BC interfacial interdiffusion: the interdiffusion zone (IDZ) and secondary reaction zone (SRZ) grow continuously (SRZ growing faster), and linear topologically close-packed (TCP) phases precipitate in the SRZ, spreading throughout the substrate and impairing high-temperature mechanical properties. Specifically, DD9’s IDZ growth rate is faster than DD6’s in the first 800 h of oxidation but slows below DD6’s afterward, reflecting DD9’s superior long-term oxidation resistance due to better temperature resistance and high-temperature stability. This study clarifies key high-temperature service disadvantages of the two systems, providing experimental support for coated turbine blade life evaluation and a theoretical basis for optimizing third-generation single-crystal superalloy-TBC systems to enhance high-temperature service stability.
Details
Investigations;
Oxidation resistance;
Single crystals;
Mixed oxides;
High temperature;
Airplane engines;
Protective coatings;
Cracking (fracturing);
Thermal barrier coatings;
Damage;
Research & development--R&D;
Superalloys;
Corrosion;
Aircraft;
Turbines;
Comparative studies;
Oxidation;
Substrates;
Interdiffusion;
Thermal barriers;
Aluminum oxide;
Turbine blades;
Spallation;
Stability;
Nickel;
Alloys;
Microstructure
; Sun, Fan 3 ; Jin Xiaochao 2
; Zhang, Chao 4
1 School of Civil Aviation, Northwestern Polytechnical University, Xi’an 710072, China; [email protected], Key Laboratory on the Impact Protection and Safety Assessment of Civil Aviation Vehicle, Taicang 215400, China
2 Xi’an Key Laboratory of Extreme Environment and Protection Technology, School of Aerospace Engineering, Xi’an Jiaotong University, Xi’an 710049, [email protected] (X.J.)
3 National Key Laboratory of Energetic Materials, Xi’an Modern Chemistry Research Institute, Xi’an 710065, China; [email protected]
4 School of Civil Aviation, Northwestern Polytechnical University, Xi’an 710072, China; [email protected], Key Laboratory on the Impact Protection and Safety Assessment of Civil Aviation Vehicle, Taicang 215400, China, School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China