Three-dimensional simulation of residual stresses in plasma sprayed thermal barrier coatings

2003 ◽  
Vol 58 (3) ◽  
pp. 38
Keyword(s):  
Residual Stresses ◽  
Thermal Barrier Coatings ◽  
Three Dimensional ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Dimensional Simulation ◽  
Plasma Sprayed

Modeling Effects of Material Properties and Three-Dimensional Surface Roughness on Thermal Barrier Coatings

2000 ◽  
Vol 645 ◽  
Author(s):  
Michael L. Glynn ◽  
K.T. Ramesh ◽  
P.K. Wright ◽  
K.J. Hemker
Keyword(s):  
Surface Roughness ◽  
Residual Stresses ◽  
Thermal Barrier Coatings ◽  
Material Properties ◽  
Bond Coat ◽  
Coefficient Of Thermal Expansion ◽  
Three Dimensional ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Dimensional Surface

ABSTRACTThermal barrier coatings (TBCs) are known to spall as a result of the residual stresses that develop during thermal cycling. TBC's are multi-layered coatings comprised of a metallic bond coat, thermally grown oxide and the ceramic top coat, all on top of a Ni-base superalloy substrate. The development of residual stresses is related to the generation of thermal, elastic and plastic strains in each of the layers. The focus of the current study is the development of a finite element analysis (FEA) that will model the development of residual stresses in these layers. Both interfacial roughness and material parameters (e.g., modulus of elasticity, coefficient of thermal expansion and stress relaxation of the bond coat) play a significant role in the development of residual stresses. The FEA developed in this work incorporates both of these effects and will be used to study the consequence of interface roughness, as measured in SEM micrographs, and material properties, that are being measured in a parallel project, on the development of these stresses. In this paper, the effect of an idealized three-dimensional surface roughness is compared to residual stresses resulting from a grooved surface formed by revolving a sinusoidal wave about an axis of symmetry. It is shown that cylindrical and flat button models give similar results, while the 3-D model results in stresses that are significantly larger than the stresses predicted in 2-D.

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

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.

Collaboration Tasks on Physical and Fundamental Properties of Plasma Sprayed Thermal Barrier Coatings in Japan Society of Materials Science

2007 ◽  
Vol 353-358 ◽  
pp. 1806-1809
Author(s):  
Kazuhiro Ogawa
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Thermal Barrier Coatings ◽  
Standard Condition ◽  
Thermal Barrier ◽  
Fundamental Study ◽  
Lower Velocity ◽  
Barrier Coatings ◽  
Porosity Ratio ◽  
Plasma Sprayed

The subcommittee on superalloys and coatings, The Society for Materials and Science, Japan (JSMS) was established in 1997. As second stage of the committee, we investigated a fundamental study on thermal plasma sprayed thermal barrier coatings (TBCs). Especially, relationships between spray conditions and coating properties are discussed. It was used 4 spraying conditions such as 1) standard condition, 2) larger particle used and lower velocity, 3) normal particle used and lower velocity, and 4) standard condition and heating up the substrate to 473K. As a round robin test, porosity ratio, residual stress, and bonding strength were evaluated by several techniques for the specimens, which were sprayed by above 4 conditions. As a result, Young’s modulus, and tensile strength increased with decreasing porosity ratio. In case of tests for residual stress evaluation, as-sprayed specimens have small tensile residual stresses. After thermal exposure, residual stresses shifted to compressive.

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