Surface thermal fracture of functionally graded ceramic coatings: Effect of architecture and materials

Mathematical modeling of thermal fracture of functionally graded/homogeneous bimaterial structures with a system of arbitrarily located cracks is performed and based on the previously suggested theoretical approach [1-which used the integral equation method. It is supposed that the structure is subjected to thermal loading (a thermal flux) and mechanical loading (a tension). The properties of the functionally graded material (FGM) are described by a continuous exponential function. The main fracture characteristics (stress intensity factors and fracture angles) are presented as functions of the geometry of the problem and special inhomogeneity parameters of FGMs. Some typical crack patterns for FGM/homogeneous bimaterial structures resulting from experiments available in literature are studied in detail. Thermal fracture of actual material combinations of FGMs such as: ceramic/ceramic, e.g., TiC/SiC, MoSi2/Al2O3and MoSi2/SiC, and also ceramic/metal FGMs, e.g., zirconia/nickel and zirconia/steel, is investigated.

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Heat Insulation Performance of Functionally Graded Metal/Ceramic Coatings and Fracture Behavior under High Heat Flux

Journal of the Japan Society of Powder and Powder Metallurgy ◽

10.2497/jjspm.51.260 ◽

2004 ◽

Vol 51 (4) ◽

pp. 260-265

Author(s):

Hua-Ping Xiong ◽

Akira Kawasaki ◽

Yan-Sheng Kang ◽

Ryuzo Watanabe

Keyword(s):

Heat Flux ◽

Fracture Behavior ◽

Heat Insulation ◽

Ceramic Coatings ◽

High Heat ◽

Functionally Graded ◽

High Heat Flux ◽

Metal Ceramic ◽

Insulation Performance

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Multiple Surface Cracking and Its Effect on Interface Cracks in Functionally Graded Thermal Barrier Coatings Under Thermal Shock

Journal of Applied Mechanics ◽

10.1115/1.1533809 ◽

2003 ◽

Vol 70 (2) ◽

pp. 234-245 ◽

Cited By ~ 21

Author(s):

S. Rangaraj ◽

K. Kokini

Keyword(s):

Thermal Shock ◽

Thermal Barrier Coatings ◽

Architectural Design ◽

Effective Properties ◽

Mean Field ◽

Functionally Graded ◽

Analytical Models ◽

Thermal Barrier ◽

Thermal Fracture ◽

Barrier Coatings

The thermal fracture behavior in functionally graded yttria stabilized zirconia–NiCoCrAlY bond coat alloy thermal barrier coatings was studied using analytical models. The response of three coating architectures of similar thermal resistance to laser thermal shock tests was considered. Mean field micromechanics models were used to predict the effective thermoelastic and time-dependent (viscoplastic) properties of the individual layers of the graded thermal barrier coatings (TBCs). These effective properties were then utilized in fracture mechanics analyses to study the role of coating architecture on the initiation of surface cracks. The effect of the surface crack morphology and coating architecture on the propensity for propagation of horizontal delamination cracks was then assessed. The results of the analyses are correlated with previously reported experimental results. Potential implications of the findings on architectural design of these material systems for enhanced thermal fracture resistance are discussed.

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