Journal ArticleDOI
Damage Evolution and Stress Analysis in Zirconia Thermal Barrier Coatings during Cyclic and Isothermal Oxidation
TLDR
In this paper, the failure mechanisms of air-plasma-sprayed ZrO{sub 2} thermal barrier coatings with various microstructures were studied by microscopic techniques after thermal cycling.Abstract:
The failure mechanisms of air-plasma-sprayed ZrO{sub 2} thermal barrier coatings with various microstructures were studied by microscopic techniques after thermal cycling. The elastic modulus (E) and hardness (H) of the coatings were measured as functions of the number of thermal cycles. Initially, both E and H increased by -60% with thermal cycling because of sintering effects. However, after -80 cycles (0.5 h at 980{sup o}C), the accumulated damage in the coatings led to a significant decrease of -20% of the maximum value in both E and H. These results were correlated with stresses measured by a spectroscopic technique to understand specific damage mechanisms. Stress measurement and analysis revealed that the stress distribution in the scale was a complex function of local interface geometry and damage in the top coat. Localized variations in geometry could lead to variations in measured hydrostatic stresses from -0.25 to -2.0 GPa in the oxide scale. Protrusions of the top ZrO{sub 2} coat into the bond coat were localized areas of high stress concentration and acted as damage-nucleation sites during thermal and mechanical cycling. The net compressive hydrostatic stress in the oxide scale increased significantly as the scale spalled during thermal cycling.read more
Citations
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Journal ArticleDOI
A review on failure mechanism of thermal barrier coatings and strategies to extend their lifetime
TL;DR: In this paper, the degradation and failure mechanisms of thermal barrier coating (TBC) systems are investigated, and some methods are summarized to alleviate the undesirable effects of the causes, so as to extend the lifetime of TBCs.
Journal ArticleDOI
Thermal cycling resistance of modified thick thermal barrier coatings
TL;DR: In this article, the thermal cycling properties of several modified thick thermal barrier coatings (TTBCs) were studied in three test series in which the maximum coating temperature was fixed to 1000, 1150 and 1300 °C.
Journal ArticleDOI
Modified thick thermal barrier coatings: microstructural characterization
TL;DR: In this paper, thin thermal barrier coatings were modified with laser glazing and phosphate-based sealing treatments and the surface porosity of the sealed coatings decreased significantly in all cases.
Journal ArticleDOI
Effect of substrate curvature on residual stresses and failure modes of an air plasma sprayed thermal barrier coating system
Dong Liu,M. Seraffon,M. Seraffon,Peter E J Flewitt,Nigel J. Simms,John Nicholls,David Stafford Rickerby +6 more
TL;DR: In this article, a set of aerofoil shaped air plasma sprayed thermal barrier coated (APS-TBC) specimens were adopted to investigate the stress distributions in the ceramic top coat (TC) and the thermally grown oxide (TGO), the mechanism of local crack generation and propagation at the TC/BC (bond coat) interface.
Journal ArticleDOI
Damage progression in thermal barrier coating systems during thermal cycling: A nano-mechanical assessment
Giovanni Bolelli,Maria Grazia Righi,Muhammad Zeeshan Mughal,Riccardo Moscatelli,Omar Ligabue,Nelso Antolotti,Marco Sebastiani,Luca Lusvarghi,Edoardo Bemporad +8 more
TL;DR: In this paper, the nano-mechanical properties of thermal barrier coatings (TBCs) vary during thermal cycling, as a way to shed new light on their failure mechanisms.
References
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Journal ArticleDOI
A Simple Method for Determining Elastic-Modulus–to-Hardness Ratios using Knoop Indentation Measurements
TL;DR: In this paper, a simple indentation technique for measuring the hardness-to-modulus ratio of elastic/plastic materials was developed, which is based on measurement of the elastic recovery of the in-surface dimensions of a Knoop indentation.
Journal ArticleDOI
Failure mechanisms of thermal barrier coatings exposed to elevated temperatures
Robert A. Miller,Carl E. Lowell +1 more
TL;DR: In this paper, the failure of a ZrO2-8%Y2O3/Ni-14% Al-0.1% Zr coating system on Rene 41 in Mach 0.3 burner rig tests was characterized.
Journal ArticleDOI
Stress Measurement in Single-Crystal and Polycrystalline Ceramics Using Their Optical Fluorescence
Qing Ma,David R. Clarke +1 more
TL;DR: In this article, a general methodology is developed for determining the state of stress and the numerical value of the stresses from observed shifts and broadening of optical fluorescence lines, based on the piezospectroscopic properties of single crystals.
Journal ArticleDOI
Measurement of the stress in oxide scales formed by oxidation of alumina-forming alloys
Don Mark Lipkin,David R. Clarke +1 more
TL;DR: In this paper, the authors show that the alumina scales on a variety of high-temperature alloys are found to fluoresce when illuminated with light having a frequency greater than 18,000 cm−1.
Journal ArticleDOI
Spalling failure of a thermal barrier coating associated with aluminum depletion in the bond-coat
TL;DR: In this article, the phase conversion occurs after the alumina TGO has cracked on thermal cycling and the underlying bond-coat alloy is depleted of aluminum with concurrent enrichment of the oxide by Cr, Co and Ni.
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