Influence of Substrate Condictions on Thermal-Shocking Property of Sm2Zr2O7/NiCoCrAlY Graded Thermal Barrier Coatings

The effect of substrate conditions, including material type, thickness and radius on thermal shocking properties of plasma sprayed Sm2Zr2O7/NiCoCrAlY functional graded thermal barrier coatings were analyzed by ANSYS—a finite element method software. Results show that thermal stresse in coatings increase with increasing of thermal expansion coefficients of substrates. The effect of substrate thickness can be ignored when it is greater than 20mm. Thermal stresses increase with radius increasing, however, they are almost not effected when substrate radius is over 18mm.

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Investigation about Thermal Shock Property of Plasma-Spraying Sm2Zr2O7 Thermal Barrier Coatings with Different Substrate Condictions

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.354-355.145 ◽

2011 ◽

Vol 354-355 ◽

pp. 145-148

Author(s):

Hong Song Zhang ◽

Hong Chan Sun

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Thermal Expansion ◽

Residual Stresses ◽

Plasma Spraying ◽

Thermal Barrier Coatings ◽

Thermal Barrier ◽

Shear Stresses ◽

Substrate Thickness ◽

Barrier Coatings

Effect of substrate conditions, including material type, thickness and radius of substrate, on thermal-shocking stresses of plasma spraying Sm2Zr2O7/ NiCrCoAlY TBCs was analyzed through finite element method. Results show that radial stresses decrease with time increasing, and they decrease with the increasing of distance from center to edge along radius. However, axial residual stresses increse abruptly at the edge of specimen. All residual stresses increse with incresing of thermal expansion coefficient of substrate. Radial stresses increase with substrate thickness increasing, however, they are not effectd by substrate thickness if it is great than 20mm.and axial residual stresses and shear stresses are not effected by the substrate thickness. The maximum values of axial stresses and shear stresses were not effected by sustrate radius. and values of radial stresses remian invariable when substrate radius is over 18mm.

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Investigation of Strontium-Niobium Oxides for Application to Thermal Barrier Coatings

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.317-318.517 ◽

2006 ◽

Vol 317-318 ◽

pp. 517-520 ◽

Cited By ~ 1

Author(s):

Masato Shida ◽

Katsunori Akiyama ◽

Ichiro Nagano ◽

Yuichiro Murakami ◽

Satoshi Ohta

Keyword(s):

Thermal Expansion ◽

Thermal Barrier Coatings ◽

Solid Solutions ◽

Thermal Barrier ◽

Barrier Coatings ◽

Niobium Oxides ◽

Thermal Expansion Coefficients ◽

Expansion Coefficients ◽

Thermal Conductivities

We have been trying to find new oxide compounds with large thermal expansion coefficients and low thermal conductivities by means of a material calculation technique. Among thousands of compounds in the databases, we found that there were some materials with low thermal conductivities and large thermal expansion coefficients in the group of strontium-niobium oxides. For example, Sr4Nb2O9 has a thermal expansion coefficient of 14.510-6 / and thermal conductivity of 1.0 W/mK, although a slight amount of other phases appear during long-term annealing. These thermal properties are better than those of yttria-stabilized zirconia, which is the standard material for thermal barrier coatings. To prevent the precipitation of other phases, we prepared the solid solutions, Sr4Nb2-xMxO9. In this study, the thermal conductivities and thermal expansion coefficients of these solid solutions were measured, and their thermal stabilities were evaluated by long-term annealing.

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A Promising Sm1.9Ca0.1Zr2O6.95 Ceramic for Thermal Barrier Coatings

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.336-338.1762 ◽

2007 ◽

Vol 336-338 ◽

pp. 1762-1763

Author(s):

Qiang Xu ◽

Wei Pan ◽

Chun Lei Wan ◽

Long Hao Qi ◽

He Zhuo Miao

Keyword(s):

Thermal Expansion ◽

Thermal Barrier Coatings ◽

Solid State Reaction Method ◽

Thermal Barrier ◽

Barrier Coatings ◽

Reaction Method ◽

X Ray ◽

Thermal Expansion Coefficients ◽

Calcium Cation ◽

Expansion Coefficients

Sm1.9Ca0.1Zr2O6.95 ceramic was sintered at 1600°C for 10 h in air by solid-state reaction method. The phase structure and thermal expansion coefficient were measured by XRD and a high-temperature dilatometry, respectively. The results show that the crystal structure of Sm1.9Ca0.1Zr2O6.95 ceramic is still pyrochlore. The doping with calcium cation leads to a shift of the X-ray spectrum of Sm1.9Ca0.1Zr2O6.95 ceramic to lower 2θ values. The experiments also show that the thermal expansion coefficients of Sm1.9Ca0.1Zr2O6.95 ceramic are higher than those of Sm2Zr2O7 ceramic. These results are related to the vacancy induced by doped calcium cation in the samarium lattice.

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Modeling and Characterization of Residual Stresses and Microstructure in Thermal Barrier Coatings after Plasma Spraying

Thermal Spray 1996: Proceedings from the National Thermal Spray Conference ◽

10.31399/asm.cp.itsc1996p0941 ◽

1996 ◽

Author(s):

C. Persson ◽

P. Bengtsson ◽

J. Wigren ◽

D. Greving

Keyword(s):

Residual Stresses ◽

Thermal Barrier Coatings ◽

Thermal Stresses ◽

Element Model ◽

Thermal Barrier ◽

Barrier Coatings ◽

Bond Coating ◽

Plasma Sprayed ◽

Removal Technique

Abstract Thermal barrier coatings with a zirconia top coating and a NiCoCrAlY bond coating were plasma sprayed onto a nickelbase alloy. The pre-heating of the bond coated substrates and the cooling during the top coating spraying were varied to produce five different spray sets. A finite element model was developed to predict the heat transfer and the resulting thermal stresses during the spraying. A layer removal technique was used to measure the residual stresses in the as-sprayed samples. The measurements revealed low residual stresses in the top coatings and tensile stresses in the order of 150 MPa in the bond coating. A correlation between the measured top coating residual stresses and the substrate temperature in the end of the top coating spraying was found. In general, good agreement between modelled and measured residual stresses was found. The top coatings were found to contain vertical microcracks and the densities of the cracks were point-counted in the spray sets. A slight increase in microcrack densities was found as the spraying was performed onto a colder substrate. The densities of vertical microcracks were correlated to modelled in-elastic strain in the top coatings.

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Initiation of Surface and Interface Edge Cracks in Functionally Graded Ceramic Thermal Barrier Coatings

Journal of Engineering Materials and Technology ◽

10.1115/1.2805987 ◽

1997 ◽

Vol 119 (2) ◽

pp. 148-152 ◽

Cited By ~ 15

Author(s):

Klod Kokini ◽

Michael Case

Keyword(s):

Thermal Barrier Coatings ◽

Thermal Stresses ◽

Functionally Graded ◽

Thermal Barrier ◽

Barrier Coatings ◽

Surface And Interface ◽

Probability Of Survival ◽

Edge Cracks ◽

Plasma Sprayed ◽

Interface Edge

The initiation of surface and interface edge cracks in functionally graded ceramic thermal barrier coatings resulting from the application of a thermal load is studied. For a given specimen configuration, the singular behavior of the thermal stresses is analytically determined in terms of a singularity power β and pseudo-stress intensity factors K1 and K2. Crack initiation at the surface at the interface is related to the surface temperature and the temperature difference between the surface of the coating and the substrate. The experimental results are used to provide Weibull curves for the probability of survival of plasma sprayed mullite and CoCrAlY coating systems.

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Analysis of the Stress State in Thermal Barrier Coatings during a Thermal Cycle

Thermal Spray 1996: Proceedings from the National Thermal Spray Conference ◽

10.31399/asm.cp.itsc1996p0897 ◽

1996 ◽

Author(s):

G. Jönsson ◽

C. Persson

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Stress State ◽

Residual Stresses ◽

Thermal Barrier Coatings ◽

Thermal Cycle ◽

Thermal Stresses ◽

Thermal Barrier ◽

Barrier Coatings ◽

Element Method

Abstract Thermal barriers made up by a ceramic top coating and a metallic bond coating are subjected to thermal cycles in service. The thermal stresses vary during the cycles and the residual stresses change as a result of plastic flow and creep. The stress state in thermal barrier coatings during a thermal cycle has been examined with a finite element method using temperature dependent material data. The calculated results were verified by measurements of the residual stresses with the layer removal technique before and after cycling of specimens heated in furnace with air environment. According to the simulation of a thermal cycle to 700 ° C, using a finite element method, the bond coat is approximately stress free after 1 hour dwell time. Thus, the residual stresses after a thermal cycle is a result of thermal expansion mismatch and temperature drop.

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Effect of Substrate Condictions on Thermal Shock Property of Plasma-Spraying Sm2Zr2O7 /YSZ Thermal Barrier Coatings

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.332-334.1799 ◽

2011 ◽

Vol 332-334 ◽

pp. 1799-1802

Author(s):

Hong Song Zhang ◽

Yuan Wei

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Thermal Expansion ◽

Residual Stresses ◽

Plasma Spraying ◽

Thermal Barrier Coatings ◽

Thermal Barrier ◽

Shear Stresses ◽

Substrate Thickness ◽

Barrier Coatings

Effect of substrate conditions, including material type, thickness and radius of substrate, on thermal-shocking stresses of plasma spraying Sm2Zr2O7/YSZ TBCs was analyzed through finite element method. Results show that radial stresses decrease with time increasing, and they decrease with the increasing of distance from center to edge along radius. However, axial residual stresses increse abruptly at the edge of specimen. All residual stresses increse with incresing of thermal expansion coefficient of substrate. Radial stresses increase with substrate thickness increasing, however, they are not effectd by substrate thickness if it is great than 25mm.and axial residual stresses and shear stresses are not effected by the substrate thickness. The maximum values of axial stresses and shear stresses were not effected by sustrate radius. and values of radial stresses remian invariable when substrate radius is over 18mm.

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