scholarly journals Thermal fracture mechanisms in ceramic thermal barrier coatings

1997 ◽  
Vol 6 (1) ◽  
pp. 43-49 ◽  
Author(s):  
K. Kokini ◽  
B. D. Choules ◽  
Y. R. Takeuchi
Keyword(s):  
Thermal Barrier Coatings ◽  
Fracture Mechanisms ◽  
Thermal Barrier ◽  
Thermal Fracture ◽  
Barrier Coatings

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

2003 ◽  
Vol 70 (2) ◽  
pp. 234-245 ◽  
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.

A Study of Thermal Fracture in Functionally Graded Thermal Barrier Coatings Using a Cohesive Zone Model

2004 ◽  
Vol 126 (1) ◽  
pp. 103-115 ◽  
Author(s):  
Sudarshan Rangaraj ◽  
Klod Kokini
Keyword(s):  
Thermal Shock ◽  
Thermal Barrier Coatings ◽  
Cohesive Zone ◽  
Functionally Graded ◽  
Systematic Evaluation ◽  
Thermal Barrier ◽  
Zone Model ◽  
Thermal Fracture ◽  
Barrier Coatings ◽  
Separation Relation

This work describes the application of two-dimensional finite element models with a cohesive zone to study quasi-static crack extension in functionally graded Yttria stabilized Zirconia (YSZ)-Bond Coat (BC) alloy (NiCoCrAlY) thermal barrier coatings (TBC). Crack growth under a single heating-cooling cycle simulating a laser thermal shock experiment is considered. The traction-separation relations for YSZ and BC alloy are coupled to yield a traction-separation relation for the individual layers of the graded TBC. Results from laser thermal shock experiments are then used for a systematic evaluation of the material properties in this traction-separation relation. The effective work of separation for YSZ-BC alloy composites, which is indicative of the material’s fracture toughness, is then computed. The model is then used to predict the surface thermal fracture response in a graded TBC having an architecture different from the coatings that were used to evaluate the cohesive properties. These model predictions are then compared with results from laser thermal shock experiments.

Thermal fracture of interfaces in precracked thermal barrier coatings

2002 ◽  
Vol 323 (1-2) ◽  
pp. 70-82 ◽  
Author(s):  
Klod Kokini ◽  
Anuradha Banerjee ◽  
Thomas A Taylor
Keyword(s):  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Thermal Fracture ◽  
Barrier Coatings

Thermal Fracture of Multilayer Ceramic Thermal Barrier Coatings

1994 ◽  
Vol 116 (1) ◽  
pp. 266-271 ◽  
Author(s):  
Y. R. Takeuchi ◽  
K. Kokini
Keyword(s):  
Steady State ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Thermal Fracture ◽  
Surface Cracks ◽  
Controlled Experiments ◽  
Barrier Coatings ◽  
Thermal Transients ◽  
Out Of Plane ◽  
Multilayer Ceramic

Controlled experiments and a corresponding analytical model were developed to investigate the reasons for crack initiation in multilayer ceramic thermal barrier coatings. The experiments and model determined that surface cracks form as a result of tensile stresses created following stress relaxation in the ceramic at steady-state high temperatures (about 900°C–1100°C). Interface cracks generated by out-of-plane stresses are affected by the presence of these surface cracks and thermal transients and, possibly, edge effects.

Thermal Fracture of Multilayer Ceramic Thermal Barrier Coatings

1992 ◽  
Author(s):  
Y. R. Takeuchi ◽  
K. Kokini
Keyword(s):  
Steady State ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Thermal Fracture ◽  
Surface Cracks ◽  
Controlled Experiments ◽  
Barrier Coatings ◽  
Thermal Transients ◽  
Out Of Plane ◽  
Multilayer Ceramic

Controlled experiments and a corresponding analytical model were developed to investigate the reasons for crack initiation in multilayer ceramic thermal barrier coatings. The experiments and model determined that surface cracks form as a result of tensile stresses created following stress relaxation in the ceramic at steady state high temperatures (about 900°C-1100°C). Interface cracks generated by out of plane stresses are affected by the presence of these surface cracks and thermal transients and, possibly, edge effects.

Sign in / Sign up

Export Citation Format

Share Document