Porous α-Al2O3 thermal barrier coatings with dispersed Pt particles prepared by cathode plasma electrolytic deposition

Thermal barrier coatings (TBC) have been used to improve the efficiency of turbine engine by providing the capability to sustain significant temperature gradient across the coating. TBC failure occurs easily at the interface between the metallic bondcoat and topcoat. Alumina was proposed as a potential candidate as an interlayer to improve the oxidation resistance of thermal barrier coating due to its low oxygen diffusivity against the harsh environment. The mechanical properties, thermal behaviour and high temperature oxidation resistance of the coatings formed by gas tunnel type plasma spraying were investigated in this study. The results showed that this system exhibits the improvement of mechanical properties of the coating and oxidation resistance. This interlayer is preferred in order to minimize the detrimental effect of phase transformation of γ- Al2O3 to α-Al2O3.

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Diffusion of Al, O, Pt, Hf, and Y atoms on α-Al2O3(0001): implications for the role of alloying elements in thermal barrier coatings

Journal of Materials Chemistry ◽

10.1039/c0jm02212h ◽

2011 ◽

Vol 21 (5) ◽

pp. 1447-1456 ◽

Cited By ~ 29

Author(s):

Ivan Milas ◽

Berit Hinnemann ◽

Emily A. Carter

Keyword(s):

Thermal Barrier Coatings ◽

Alloying Elements ◽

Thermal Barrier ◽

Barrier Coatings ◽

Α Al2o3

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Effects of Al Sputtering Film on the Oxidation Behavior of NiCrAlY Bondcoat

Coatings ◽

10.3390/coatings10040376 ◽

2020 ◽

Vol 10 (4) ◽

pp. 376

Author(s):

Yong Zhang ◽

Gengfei Zhang ◽

Qiang Yang ◽

Weicheng Cao ◽

Jian Pu ◽

...

Keyword(s):

Oxidation Resistance ◽

Thermal Barrier Coatings ◽

Cyclic Oxidation ◽

Oxidation Behavior ◽

Mixed Oxides ◽

Oxidation Mechanism ◽

Thermal Barrier ◽

Barrier Coatings ◽

Al Content ◽

Α Al2o3

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.

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Characterization of thermal barrier coatings formed by electon-beam physical vapor deposition (EB-PVD)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015410x ◽

1989 ◽

Vol 47 ◽

pp. 426-427

Author(s):

Ozer Unal

Keyword(s):

Thermal Barrier Coatings ◽

Physical Vapor Deposition ◽

Ceramic Coating ◽

High Vacuum ◽

Ceramic Coatings ◽

High Energy ◽

Thermal Barrier ◽

Protective Oxide ◽

Barrier Coatings ◽

Energy Beam

Interest in ceramics as thermal barrier coatings for hot components of turbine engines has increased rapidly over the last decade. The primary reason for this is the significant reduction in heat load and increased chemical inertness against corrosive species with the ceramic coating materials. Among other candidates, partially-stabilized zirconia is the focus of attention mainly because ot its low thermal conductivity and high thermal expansion coefficient.The coatings were made by Garrett Turbine Engine Company. Ni-base super-alloy was used as the substrate and later a bond-coating with high Al activity was formed over it. The ceramic coatings, with a thickness of about 50 μm, were formed by EB-PVD in a high-vacuum chamber by heating the target material (ZrO2-20 w/0 Y2O3) above its evaporation temperaturef >3500 °C) with a high-energy beam and condensing the resulting vapor onto a rotating heated substrate. A heat treatment in an oxidizing environment was performed later on to form a protective oxide layer to improve the adhesion between the ceramic coating and substrate. Bulk samples were studied by utilizing a Scintag diffractometer and a JEOL JXA-840 SEM; examinations of cross-sectional thin-films of the interface region were performed in a Philips CM 30 TEM operating at 300 kV and for chemical analysis a KEVEX X-ray spectrometer (EDS) was used.

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