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Research Papers: Gas Turbines: Manufacturing, Materials, and Metallurgy

Fabrication and Characterization of Additive Manufactured Nickel-Based Oxide Dispersion Strengthened Coating Layer for High-Temperature Application

[+] Author and Article Information
Zheng Min

Department of Mechanical Engineering
and Material Science,
University of Pittsburgh,
Pittsburgh, PA 15261
e-mail: zhm10@pitt.edu

Sarwesh Narayan Parbat

Department of Mechanical Engineering and
Material Science,
University of Pittsburgh,
Pittsburgh, PA 15261

Li Yang, Minking K. Chyu

Department of Mechanical Engineering
and Material Science,
University of Pittsburgh,
Pittsburgh, PA 15261

Bruce Kang

Mechanical and Aerospace Engineering
Department,
West Virginia University,
Morgantown, WV 26506

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 7, 2017; final manuscript received August 30, 2017; published online January 23, 2018. Editor: David Wisler.

J. Eng. Gas Turbines Power 140(6), 062101 (Jan 23, 2018) (7 pages) Paper No: GTP-17-1318; doi: 10.1115/1.4038351 History: Received July 07, 2017; Revised August 30, 2017

Increasing turbine inlet temperature is important for improving the efficiency of gas turbine engine. Elevated thermal load causes severe oxidation and corrosion for base alloy in turbine airfoils. To survive in this extreme high-temperature and harsh oxidation environment, both outside protection like thermal barrier coatings (TBC) and inside air cooling have been applied to turbine blades. Significantly more protection can be achieved if the cooling channels are embedded near surface, constructed partially by the coating system and partially by the superalloy substrate. However, neither the ceramic coating layer nor the metallic bond coating layer in current TBC system can provide structural support to such internal cooling channels. Development of structural bond coating layers consequently becomes one of the key technologies to achieve this goal. The present study proposed a method to fabricate structural coating layers on top of turbine blades with the aid of additive manufacturing (AM) and oxide dispersion strengthened (ODS) nickel-based alloy. ODS powder comprised of evenly distributed host composite particles (Ni, Al, Cr) with oxide coating layers (Y2O3) was subjected to a direct metal laser sintering (DMLS) process to fabricate a desirable structural coating layer above nickel-based superalloy substrates. Systematic experimental tests were carried out focusing on the interface adhesion, mechanical strength, microstructure, and surface finish of the ODS coating layer. Based on characterization results from indentation tests and microscopy observations, an optimal coating quality was obtained under ∼250 W laser power. The selected samples were then characterized under isothermal conditions of 1200 °C for 2000 h. Scanning electron microscope (SEM) observations and energy-dispersive X-ray spectroscopy (EDX) analysis were conducted in different stages of the oxidation process. Results indicated a formation of Al2O3 scale on top of the ODS coating layer at early stage, which showed long-term stability throughout the oxidation test. The formation of a stable alumina scale is acting as a protective layer to prevent oxygen penetrating the top surface. Spallation of part of nickel oxide and chromium oxide is observed but the thickness of oxide scale is almost no change. In addition, the observed adhesion between ODS coating layer and substrate was tight and stable throughout the entire oxidation test. The present study has provided strong proof that additive manufacturing has the capability to fabricate structural and protective coating layers for turbine airfoils.

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References

Padture, N. P. , Gell, M. , and Jordan, E. H. , 2002, “ Thermal Barrier Coatings for Gas-Turbine Engine Applications,” Science, 296(5566), pp. 280–284. [CrossRef] [PubMed]
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Sun, D. , Liang, C. , Shang, J. , Yin, J. , Song, Y. , Li, W. , Liang, T. , and Zhang, X. , 2016, “ Effect of Y2O3 Contents on Oxidation Resistance at 1150 °C and Mechanical Properties at Room Temperature of ODS Ni–20Cr–5Al Alloy,” Appl. Surf. Sci., 385, pp. 587–596. [CrossRef]
He, Y. , Huang, Z. , Qi, H. , Wang, D. , Li, Z. , and Gao, W. , 2000, “ Oxidation Behaviour of Micro-Crystalline Ni–20Cr–Y2O3 ODS Alloy Coatings,” Mater. Lett., 45(2), pp. 79–85. [CrossRef]
Kang, B. S. , Chyu, M. K. , Alvin, M. A. , and Gleeson, B. M. , 2013, “ Method of Producing an Oxide Dispersion Strengthened Coating and Micro-Channels,” U.S. Department of Energy, Washington, DC, U.S. Patent No. US8609187 B1. https://www.google.ch/patents/US8609187
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Figures

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Fig. 5

Surface hardness of depositions

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Fig. 4

Illustrative locations of micro-indentation test

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Fig. 3

Square ODS depositions on substrates

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Fig. 6

SEM and line scan positions: (a) original substrate with ODS coating and (b) substrate with ODS coating after isothermal test

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Fig. 7

Original cross section of ODS coating layer

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Fig. 8

Line scan of ODS layer

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Fig. 9

Thickness change of ODS and interface

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Fig. 2

Strip ODS depositions on substrates

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Fig. 10

Line scan of oxide scale

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Fig. 11

Oxide scale thickness change at different stages

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Fig. 12

Composition change of Al, Cr, Ni

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Fig. 13

Comparison of original surface and surface after 2000 h isothermal test (magnification: 200×)

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Fig. 15

The image processing of surface photograph

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Fig. 16

The ratio change of plateau part of outer surface

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Fig. 14

Micrographs and spectrum scans of top surface of ODS coating layer

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