Time-Dependent Behavior and Fracture of Functionally Graded Thermal Barrier Coatings under Thermal Shock

2005 ◽  
pp. 379-384 ◽  
Author(s):  
Klod Kokini ◽  
Sudarshan V. Rangaraj
Keyword(s):  
Thermal Shock ◽  
Thermal Barrier Coatings ◽  
Functionally Graded ◽  
Time Dependent ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Dependent Behavior

Time-Dependent Behavior and Fracture of Functionally Graded Thermal Barrier Coatings under Thermal Shock

2005 ◽  
Vol 492-493 ◽  
pp. 379-384 ◽  
Author(s):  
Klod Kokini ◽  
Sudarshan V. Rangaraj
Keyword(s):  
Thermal Shock ◽  
Thermal Barrier Coatings ◽  
Functionally Graded ◽  
Yttria Stabilized Zirconia ◽  
Time Dependent ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Dependent Behavior ◽  
Bond Coat Alloy

The thermal fracture and its dependence on time-dependent behavior in functionally graded yttria stabilized zirconia - NiCoCrAlY bond coat alloy thermal barrier coatings was studied. The response of three coating architectures of similar thermal resistance to laser thermal shock tests was considered, experimentally and computationally.

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 shock of functionally graded thermal barrier coatings with similar thermal resistance

2002 ◽  
Vol 154 (2-3) ◽  
pp. 223-231 ◽  
Author(s):  
Klod Kokini ◽  
Jeffery DeJonge ◽  
Sudarshan Rangaraj ◽  
Brad Beardsley
Keyword(s):  
Thermal Resistance ◽  
Thermal Shock ◽  
Thermal Barrier Coatings ◽  
Functionally Graded ◽  
Thermal Barrier ◽  
Barrier Coatings

Thermal Shock Behavior of Nano-Structured Functionally Graded Thermal Barrier Coatings Deposited by Supersonic Plasma Spray

2007 ◽  
Vol 336-338 ◽  
pp. 2624-2627 ◽  
Author(s):  
Zhi Hai Han ◽  
Hai Jun Wang ◽  
Shi Kui Zhou ◽  
Bin Shi Xu
Keyword(s):  
Thermal Shock ◽  
Thermal Barrier Coatings ◽  
Functionally Graded ◽  
Thermal Barrier ◽  
Thermal Shock Test ◽  
Nano Structure ◽  
Barrier Coatings ◽  
Supersonic Plasma ◽  
Lower Temperature ◽  
Thermal Shock Behavior

The nano-structured functionally graded 8YSZ/NiCoCrAlY thermal barrier coatings (FG-TBCs) were prepared using a recently developed Supersonic Plasma Spraying (S-PS) system with dual powder feed ports. The alloy powders were fed into the lower temperature regions of the plasma plume through one of them to prevent it over molten and oxidation. The ceramic powders were fed into high temperature regions through another for fully melted. The thermal shock behavior of the FG-TBCs were investigated. It was found the totally 1mm thick FG-TBCs layer still maintained nano-structure form by TEM, and also exhibited a finely lamellate microstructure mixed by alloy and ceramic with gradient along the thickness direction by SEM. The FG-TBCs exhibit excellent thermal shock resistance due to it was still perfect without any spallation after thermal shock test over 200 cycles under heating by oxygenacetylene flam to 1250°C in 30s and then quenching into ambient water.

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