Microstructural Evolution of 7 wt.% Y2O3 ZrO2 Thermal Barrier Coatings due to Stress Relaxation at Elevated Temperatures and the Concomitant changes in Thermal Conductivity

Petorak, Christopher; Ilavsky, Dr. Jan; Wang, Hsin; Porter, Wallace D; Trice, Rodney

doi:10.1016/j.surfcoat.2010.06.007

Title: Microstructural Evolution of 7 wt.% Y2O3 ZrO2 Thermal Barrier Coatings due to Stress Relaxation at Elevated Temperatures and the Concomitant changes in Thermal Conductivity

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Abstract

The purpose of this study was to evaluate the combined effect of stress and temperature on the microstructure of air plasma-sprayed 7 wt.% Y{sub 2}O{sub 3}-ZrO{sub 2} thermal barrier coatings, and relate microstructural changes to the thermal conductivity, k{sub th}. To simulate TBC service conditions, stand-alone tubes of YSZ were stress relaxed, starting from a compressive stress of 60 MPa, at temperatures of 1000 C or 1200 C. The duration of the stress relaxation test was either 5 min or 3 h. Detailed scanning electron microscopy (SEM) and Porod's specific surface area (SSA) analysis of small angle neutron scattering (SANS) results were used to determine which void systems, either interlamellar pores or intralamellar cracks, contributed to the observed relaxation of stress in the coatings. SEM investigations revealed closure of intralamellar cracks located perpendicular to the stress direction. For thinner YSZ coatings, SANS measurements indicated a statistically significant reduction in the total SSA and SSA associated with intralamellar cracks after stress relaxation at the times, temperatures, and stress investigated compared to those samples that were exposed to identical times and temperatures, but no stress. The SSA associated with the interlamellar pores was not significantly smaller in YSZ coatings stress relaxed frommore »« less

Authors:

Petorak, Christopher ^[1]; Ilavsky, Dr. Jan ^[2]; Wang, Hsin ^[3]; Porter, Wallace D ^[3]; Trice, Rodney ^[1]

Purdue University
Argonne National Laboratory (ANL)
ORNL

Publication Date:: Fri Jan 01 00:00:00 EST 2010

Research Org.:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Temperature Materials Lab. (HTML)

Sponsoring Org.:: USDOE Office of Energy Efficiency and Renewable Energy (EERE)

OSTI Identifier:: 988754

DOE Contract Number:: DE-AC05-00OR22725

Resource Type:: Journal Article

Journal Name:: Surface and Coatings Technology

Additional Journal Information:: Journal Volume: 205; Journal Issue: 1; Journal ID: ISSN 0257-8972

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; YTTRIUM OXIDES; ZIRCONIUM OXIDES; PROTECTIVE COATINGS; MICROSTRUCTURE; MORPHOLOGICAL CHANGES; THERMAL CONDUCTIVITY; STRESS RELAXATION; CRACKS

Citation Formats


                    Petorak, Christopher, Ilavsky, Dr. Jan, Wang, Hsin, Porter, Wallace D, and Trice, Rodney. Microstructural Evolution of 7 wt.% Y2O3 ZrO2 Thermal Barrier Coatings due to Stress Relaxation at Elevated Temperatures and the Concomitant changes in Thermal Conductivity.  United States: N. p., 2010. 
        Web.  doi:10.1016/j.surfcoat.2010.06.007.

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                    Petorak, Christopher, Ilavsky, Dr. Jan, Wang, Hsin, Porter, Wallace D, & Trice, Rodney. Microstructural Evolution of 7 wt.% Y2O3 ZrO2 Thermal Barrier Coatings due to Stress Relaxation at Elevated Temperatures and the Concomitant changes in Thermal Conductivity.  United States.  https://doi.org/10.1016/j.surfcoat.2010.06.007

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                    Petorak, Christopher, Ilavsky, Dr. Jan, Wang, Hsin, Porter, Wallace D, and Trice, Rodney. 2010.  
        "Microstructural Evolution of 7 wt.% Y2O3 ZrO2 Thermal Barrier Coatings due to Stress Relaxation at Elevated Temperatures and the Concomitant changes in Thermal Conductivity".  United States.  https://doi.org/10.1016/j.surfcoat.2010.06.007.

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@article{osti_988754,

  title        = {Microstructural Evolution of 7 wt.% Y2O3 ZrO2 Thermal Barrier Coatings due to Stress Relaxation at Elevated Temperatures and the Concomitant changes in Thermal Conductivity},

  author       = {Petorak, Christopher and Ilavsky, Dr. Jan and Wang, Hsin and Porter, Wallace D and Trice, Rodney},

  abstractNote = {The purpose of this study was to evaluate the combined effect of stress and temperature on the microstructure of air plasma-sprayed 7 wt.% Y{sub 2}O{sub 3}-ZrO{sub 2} thermal barrier coatings, and relate microstructural changes to the thermal conductivity, k{sub th}. To simulate TBC service conditions, stand-alone tubes of YSZ were stress relaxed, starting from a compressive stress of 60 MPa, at temperatures of 1000 C or 1200 C. The duration of the stress relaxation test was either 5 min or 3 h. Detailed scanning electron microscopy (SEM) and Porod's specific surface area (SSA) analysis of small angle neutron scattering (SANS) results were used to determine which void systems, either interlamellar pores or intralamellar cracks, contributed to the observed relaxation of stress in the coatings. SEM investigations revealed closure of intralamellar cracks located perpendicular to the stress direction. For thinner YSZ coatings, SANS measurements indicated a statistically significant reduction in the total SSA and SSA associated with intralamellar cracks after stress relaxation at the times, temperatures, and stress investigated compared to those samples that were exposed to identical times and temperatures, but no stress. The SSA associated with the interlamellar pores was not significantly smaller in YSZ coatings stress relaxed from 60 MPa at 1200 C for 3 h compared to as-sprayed coatings. The thermal conductivity of the coatings was strongly influenced by stress, with increases in kth observed after only 5 min at 60 MPa and 1200 C. Reductions in the total SSA were directly linked to increases in k{sub th}.},

  doi          = {10.1016/j.surfcoat.2010.06.007},

  url          = {https://www.osti.gov/biblio/988754},
  journal      = {Surface and Coatings Technology},

  issn         = {0257-8972},

  number       = 1,

  volume       = 205,

  place        = {United States},

  year         = {Fri Jan 01 00:00:00 EST 2010},

  month        = {Fri Jan 01 00:00:00 EST 2010}

}

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