Abstract
Thermal conductivity of porous thermal barrier coatings was evaluated using a newly developed five-phase model. It was demonstrated that porosities distributed in coating strongly affect thermal conductivity. The decisive reason for this change in thermal conductivity can be traced back to defect morphology and its orientation, depending on the coating deposition technique and process parameters used during deposition. In this paper, the Bruggeman’s two-phase model was used as a reference, and a five-phase model was developed to evaluate the thermal conductivity of porous coatings. This approach uses microstructural details of the shape, size, orientation and volumetric fraction of defects of coatings as input parameters. The proposed model can predict thermal conductivity values better than the previous two-phase model.
Highlights
The progression in engineering alloys led to the design and development of the present era turbine engines [1]
The performance of the thermal barrier coating (TBC) is related to porosity; it became essential to model the thermal properties according to the porosity distribution
In most of the cases, the values obtained from the five-phase modelling are grey bars represent the thermal conductivity obtained from the four-phase model for composite closer to the experimental values, neglecting the outlier results of 22MSZ
Summary
The progression in engineering alloys led to the design and development of the present era turbine engines [1]. The efficiency of a gas turbine engine can be increased with the selection of material combination that holds a low thermal conductivity over a specific elevated temperature range [30,31,32] This holds true in the case of 8YSZ under prolonged heating. Some of the advanced coating techniques such as the solution precursor plasma spray (SPS) method provides the ability to develop a wide range of microstructures that may have more splats with a structure similar to EB-PVD These kinds of coatings can be deposited at an ultra-fine level that will have a longer life than EB-PVD under set conditions [42,43,44]. In this paper, a brief introduction to Bruggeman’s two-phase is presented and the two-phase model as a reference, and a five-phase model to predict the thermal conductivity of porous coatings is developed and applied
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