Thermal expansion behavior of new Co-based alloys and implications for coatings

SURFACE & COATINGS TECHNOLOGY

卷:289

Article

Jackson, R. Wesley¹  Titus, Michael S.¹  Begley, Matthew R.^1,2  Pollock, Tresa M.¹ 

[1] Univ Calif Santa Barbara, Dept Mat, Santa Barbara, CA 93106 USA

[2] Univ Calif Santa Barbara, Dept Mech Engn, Santa Barbara, CA 93106 USA

关键词: Cobalt;    Superalloy, thermal expansion (CTE);    Thermal barrier coating (TBC);    Delamination;   

DOI  :  10.1016/j.surfcoat.2015.12.083

来源: Elsevier

【 摘 要 】

The thermal expansion behavior of five gamma'-(L1(2)) containing Co-based superalloys was measured using push-rod dilatometry. These results were analyzed to determine the mean coefficient of thermal expansion (CTE), the instantaneous CTE, and gamma'-solvus temperature of the alloys. The CTE was found to depend strongly on the gamma'-solvus temperature. In turbine applications, these alloys will be part of a multilayer system that generates thermal stresses due to the CTE mismatch between the components. To investigate this phenomenon, the CTE data was incorporated into a thermo-mechanical model to calculate the energy release rate (ERR) for the delamination of coatings from these alloys. The ERR of a thermally grown oxide (TGO) formed on the bare and bond coated Co-based alloys was determined as a function of superalloy and bond coat CTE. The ERR of a thermal barrier coating (TBC) was evaluated as a function of temperature, superalloy LIE, and coating thickness. The ERR was found to be about 1.5 x greater in Co-based superalloys compared to Ni-based superalloys cooled from T = 1100 degrees C to ambient. Strategies for reducing the driving force for delamination are discussed. (C) 2016 Elsevier B.V. All rights reserved.

【 授权许可】

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