Effects of thermal gradient and residual stresses on thermal barrier coating fracture
TL;DR: In this article, the authors used finite element models to identify the driving mechanisms which lead to internal crack growth and failure in the thermally sprayed coatings and found that the energy release rate of large cracks can reach close to fracture toughness of ceramic coatings.
About: This article is published in Mechanics of Materials.The article was published on 1998-02-01. It has received 106 citations till now. The article focuses on the topics: Residual stress & Thermal barrier coating.
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TL;DR: In this article, a numerical study using finite element analysis (FEA) was performed to investigate the effects of system architecture on the residual stresses developed in functionally graded-thermal barrier coatings (FG-TBCs) and in a typical duplex TBC comprising of NiCoCrAlY bondcoat and ZrO2 topcoat.
164 citations
TL;DR: In this paper, three possible causes of internal delamination failures in thermal barrier coating (TBC) systems are analyzed and the results of these analyses, when used in combination with available properties for the TBC, strongly suggest that the second mechanism (b) predominates in all reasonable scenarios.
Abstract: Thermal barrier coating (TBC) systems are susceptible to delamination failures in the presence of a large thermal gradient. These failures, which occur within the TBC layer, are very different in character from those associated with the thermally grown oxide. Three possible causes of internal delamination are analyzed. In all cases, the thermomechanical properties of the TBC are allowed to vary because of sintering. (a) One mechanism relates to exfoliation of an internal separation in the TBC due to a through thickness heat flux. (b) Another is concerned with edge-related delamination within a thermal gradient. (c) The third is a consequence of sintering-induced stresses. The results of these analyses, when used in combination with available properties for the TBC, strongly suggest that the second mechanism (b) predominates in all reasonable scenarios. Consequences for the avoidance of this failure mode are discussed.
155 citations
TL;DR: In this paper, the authors describe the development and application of a general domain integral method to obtain J -values along crack fronts in three-dimensional configurations of isotropic, functionally graded materials (FGMs).
148 citations
Cites background from "Effects of thermal gradient and res..."
...…of standard analysis techniques to cracks in FGMs. Delamination and cracking of FGMs at coating/substrate interfaces due to thermal loads are the focus of investigations by Lee and Erdogan (1995), Bao and Cai (1997), Lee and Erdogan (1998), Quian et al. (1998), and Gaudette et al. (2001)....
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TL;DR: In this paper, the failure mechanism of YSZirconia-stabilized thermal barrier coatings (YSZ-TBCs) and corresponding methods for lengthening the lifetime of these TBCs are discussed.
Abstract: Thermal barrier coatings (TBCs), which protect metallic components from high-temperature environments, have been widely applied to the fields of high-temperature and corrosion-resistant structural parts such as gas turbine engines, diesel engines, and power generation systems. Yttria-stabilized zirconia (YSZ) is one of the most widely used materials for TBCs owing to its excellent shock resistance, low-thermal conductivity, and relatively high coefficient of thermal expansion. In this paper the properties of YSZ and the recent developments of YSZ-TBCs are reviewed. The failure mechanism of YSZ-TBCs and corresponding methods for lengthening the lifetime of YSZ-TBCs are discussed. The advantages of graded thermal barrier coatings and the problems in processing are elucidated.
146 citations
TL;DR: In this paper, a gradient thermal cycling test was performed on atmospheric plasma-sprayed thermal barrier coatings (TBCs) with different thermally grown oxide (TGO) thicknesses.
Abstract: Gradient thermal cycling test was performed on atmospheric plasma-sprayed (APS) thermal barrier coatings (TBCs) with different thermally grown oxide (TGO) thicknesses. The TBCs with a thickness of TGO from 1.3 μm to 7.7 μm were prepared by controlling isothermal oxidation time of cold-sprayed MCrAlY bond coat. The gradient thermal cycling test was performed at a peak surface temperature of 1150°C with 150°C difference across 250 μm thick YSZ with a duration of 240 s for each cycle. Results indicate that the thermal cyclic lifetime of APS TBCs is significantly influenced by TGO thickness. When initial TGO thickness increases from 1.3 μm to 7.7 μm, the thermal cyclic lifetime decreases following a power functions by a factor of about 20. It was revealed that there exists a critical TGO thickness over which the thermal cyclic lifetime is reduced more significantly with the increase in TGO thickness. Moreover, two typical failure modes were observed. The failure mode changes from the cracking within APS YSZ at a TGO thickness less than the critical value to through YSZ/TGO interface at TGO thickness range higher than the critical value.
140 citations
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TL;DR: In this article, a (area/volume) domain integral expression for the energetic force in a thermally stressed body is derived based on a line-integral expression for energy release rate in terms of crack tip fields, which is valid for general material response.
Abstract: Based on a line-integral expression for the energy release rate in terms of crack tip fields, which is valid for general material response, a (area/volume) domain integral expression for the energetic force in a thermally stressed body is derived. The general three-dimensional finite domain integral expression and the two-dimensional and axisymmetric specializations for the energy release rate are given. The domain expression is naturally compatible with the finite element formulation of the field equations. As such it is ideally suited for efficient and accurate calculation of the pointwise values of the energy release rate along a three-dimensional crack front. The finite element implementation of the domain integral corresponds to the virtual crack extension technique. Procedures for calculating the energy release rate using the numerically determined field solutions are discussed. For illustrative purposes several numerical examples are presented.
762 citations
TL;DR: In this article, thin thermal barrier coatings (TBCs) for protecting aircraft turbine-section airfoils are examined, focusing on those advances that led first to TBC use for component life extension and more re-cently as an integral part of airfoil design.
Abstract: Thin thermal barrier coatings (TBCs) for protecting aircraft turbine section airfoils are examined. The discussion focuses on those advances that led first to TBC use for component life extension and more re-cently as an integral part of airfoil design. Development has been driven by laboratory rig and furnace testing, corroborated by engine testing and engine field experience. The technology has also been sup-ported by performance modeling to demonstrate benefits and life modeling for mission analysis. Factors that have led to the selection of current state-of-the-art plasma-sprayed and physical-vapor-deposited zirconia-yttria/MCrAlX TBCs are emphasized, as are observations fundamentally related to their behav-ior. Current directions in research into TBCs and recent progress at NASA are also noted.
762 citations
Additional excerpts
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Book•
01 Jan 2001
TL;DR: In this paper, the authors provide the first unified treatment of an important interdisciplinary field, the field of bioinformatics, in a unified eight-volume reference work, with a focus on biomedical applications.
Abstract: This major eight-volume reference work provides the first unified treatment of an important interdisciplinary field.
503 citations
TL;DR: In this article, the development of porosity and the very fine voids formed by incomplete inter-splat contact is discussed, and the strong relation between porosity with mechanical and thermal properties of ceramic coatings is reviewed.
Abstract: The present understanding of the plasma-sprayed coating formation process is reviewed. The development of porosity, and the very fine voids formed by incomplete inter-splat contact is discussed. The strong relation between porosity and mechanical and thermal properties of ceramic coatings is reviewed. Some of the controlling factors for the grain size and crystal structure within the deposited splats are discussed, particularly in reference to zirconia coatings.
387 citations
"Effects of thermal gradient and res..." refers background in this paper
...These values are Žobtained from various sources Siemers and Melan, 1983; McPherson, 1989; Brandon and Taylor, 1989; Brandes et al., 1992; Illavsky et al., 1993; Cook et .al., 1994 ....
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