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Research Papers: Gas Turbines: Structures and Dynamics

Isothermal and Cyclic Oxidation Performance of Vertically Cracked and Columnar Thermal Barrier Coating Structures Produced Using Axial Suspension Plasma Spraying Process

[+] Author and Article Information
Xiaolong Li

Department of Mechanical and
Aerospace Engineering,
Carleton University,
1125 Colonel By Drive,
Ottawa, ON K1S 5B6, Canada
e-mail: XiaolongLi@cmail.carleton.ca

Xiao Huang

Department of Mechanical and
Aerospace Engineering,
Carleton University,
1125 Colonel By Drive,
Ottawa, ON K1S 5B6, Canada
e-mail: Xiao.Huang@carleton.ca

Qi Yang

Aerospace Portfolio,
National Research Council of Canada,
1200 Montreal Road,
Ottawa, ON K1A 0R6, Canada
e-mail: Qi.Yang@nrc-cnrc.gc.ca

Zhaolin Tang

Northwest Mettech,
467 Mountain Highway,
North Vancouver, BC V7J 2L3, Canada
e-mail: zhaolin.tang@mettech.com

Contributed by the Manufacturing Materials and Metallurgy Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 2, 2015; final manuscript received July 14, 2015; published online August 25, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(1), 012506 (Aug 25, 2015) (7 pages) Paper No: GTP-15-1229; doi: 10.1115/1.4031240 History: Received July 02, 2015; Revised July 14, 2015

Oxidation performance of thermal barrier coatings (TBCs) deposited by the axial suspension plasma spraying (ASPS) method was evaluated under isothermal and cyclic conditions with a peak temperature of 1080 °C. The TBC systems are based on two nickel-based superalloy substrates (CMSX-4 and IN738LC), platinum aluminide bond coat (BC), and yttria-stabilized zirconia (8YSZ) top coat (TC) of either vertically cracked (VC) or columnar structure. Samples with IN738LC substrate exhibited longer isothermal oxidation lives whereas the ones with CMSX-4 substrate showed greater cyclic oxidation lives. Outward diffusion of W and Ta in TBC systems containing CMSX-4 was found to have progressed to the interface between thermally grown oxide (TGO) and TC; this has contributed to the reduced isothermal oxidation life. The longer cyclic oxidation lives of TBC systems with CMSX-4 were attributed to less coefficient and thermal expansion (CTE) mismatch between coating layers (reduced strain energy) and better creep resistance of diffusional BC on CMSX-4, hence less TGO rumpling. TBC systems with columnar YSZ had longer isothermal oxidation lives while those with VC YSZ seemed to result in longer cyclic lives.

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Copyright © 2016 by ASME
Topics: oxidation , Coatings
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References

Figures

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Fig. 3

Microstructures of IN738LC with VC YSZ after isothermal oxidation test: (a)–(c) BC surface after TBC spallation and (d) the backside of spalled YSZ

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Fig. 4

Microstructures of CMSX-4 with VC YSZ after isothermal oxidation test: (a) BC surface after TC spallation and (b) cross section where YSZ still remains

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Fig. 2

Cross sections of (a) VC and (b) columnar structured TBC coatings

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Fig. 1

γ/γ′ structure of (a) IN738LC and (b) CMSX-4

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Fig. 5

(a) and (b) Microstructures of IN738LC with columnar YSZ, at different magnifications, after isothermal oxidation test. Both images show continuous alumina above BC.

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Fig. 6

Microstructures of CMSX-4 with columnar YSZ after isothermal oxidation test: (a) exposed BC surface after spallation of YSZ and (b) cross section of the coating after oxidation test (BC on the lower half)

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Fig. 7

Microstructures of IN738LC with VC YSZ after cyclic oxidation test: (a) exposed BC surface after spallation and (b) backside of spalled YSZ

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Fig. 8

The appearance of CMSX-4 coated with VC YSZ: (a) as-coated, (b) after 900 cycles, and (c) after 1000 cycles

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Fig. 9

Microstructures of CMSX-4 with VC YSZ after cyclic oxidation test: (a) exposed BC surface after YSZ spallation, (b) backside of spalled YSZ, and (c) cross section showing TGO and spinel

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Fig. 10

Microstructures of the sample IN738LC with PtAl and columnar YSZ after oxidation test: (a) exposed metallic substrate, (b) backside of spalled YSZ, and (c) cross section showing large through cracks in YSZ

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Fig. 11

Microstructures of the sample CMSX-4 with PtAl and columnar YSZ after cyclic oxidation test: (a) exposed BC surface after YSZ spallation, (b) backside of spalled YSZ, and (c) through thickness cracks in YSZ

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