Abstract
In this study, the oxidation behavior of Al coated NiCrAlY bondcoat is investigated. It is known that many methods are applied to improve the lifetime of bondcoat in thermal barrier coatings. Herein, the Al sputtering method is selected to increase the Al content, which does not change the structure of bondcoat. Thin Al film of ~2 µm was sputtered on the surface of bondcoat, which improved the oxidation resistance of NiCrAlY bondcoat. Experimental results showed that, after oxidation for 200 h at 1200 °C, the formation of a dense and continuous α-Al2O3/Cr2O3 multilayer was observed on the Al coated bondcoat surface. In contrast, a mixed oxides (NiO, Cr2O3 and spinel oxides) layer formed on the surface of the as-sprayed bondcoat samples. Results of the cyclic oxidation at 1050 °C within 204 h indicated that the Al sputtering method can improve the oxidation resistance of bondcoat. This study offers a potential way to prolong the lifetime of thermal barrier coatings and provides analysis of the oxidation mechanism.
Highlights
Thermal barrier coatings (TBCs) are widely employed to thermally protect gas turbine engines.The detailed functions of TBCs include the improvement of the efficiency, durability, and properties in high temperature operation environments [1,2,3,4]
It can be observed that the total thickness of NiCrAlY bondcoat is ~150 μm, which substrate is shown
The isothermal oxidation of Al coated bondcoat samples under 1200 ◦ C for 1 h led to the formation of α-Al2 O3 and Cr2 O3
Summary
Thermal barrier coatings (TBCs) are widely employed to thermally protect gas turbine engines. The detailed functions of TBCs include the improvement of the efficiency, durability, and properties in high temperature operation environments [1,2,3,4]. TBCs generally comprise three layers, including a ceramic topcoat, an interlayer bondcoat, and a superalloy substrate. It has been proven that TBCs are used in the hot sections as an important component in protecting the gas turbines from oxidation, thermal fatigue, corrosion, wear, and erosion [5,6,7,8]. The state of art topcoat material is 6–8 wt.% yttria-stabilized zirconia (YSZ) ceramic coating, which provides the advantages of low thermal conductivity, high thermal-expansion coefficient, and high fracture toughness [9,10,11]. YSZ topcoat can be deposited by mainly two methods: electron beam physical vapor deposition (EB-PVD)
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