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A Modelling Approach to Designing Microstructures in Thermal Barrier Coatings

M. Gupta¹, P. Nylén¹, J. Wigren²

¹ University West, 46186 Trollhättan, Sweden
² Volvo Aero Corporation, 46181 Trollhättan, Sweden

received October 5,2013, received in revised form January 17, 2013, accepted February 14, 2013

Vol. 4, No. 2, Pages 85-92   DOI: 10.4416/JCST2012-00044

Abstract

Thermomechanical properties of Thermal Barrier Coatings (TBCs) are strongly influenced by coating defects, such as delaminations and pores, thus making it essential to have a fundamental understanding of microstructure-property relationships in TBCs to produce a desired coating. Object-Oriented Finite element analysis (OOF) has been shown previously as an effective tool for evaluating thermal and mechanical material behaviour, as this method is capable of incorporating the inherent material microstructure as input to the model. In this work, OOF was used to predict the thermal conductivity and effective Young's modulus of TBC topcoats. A Design of Experiments (DoE) was conducted by varying selected parameters for spraying Yttria-Stabilised Zirconia (YSZ) topcoat. The microstructure was assessed with SEM, and image analysis was used to characterize the porosity content. The relationships between microstructural features and properties predicted by modelling are discussed. The microstructural features having the most beneficial effect on properties were sprayed with a different spray gun so as to verify the results obtained from modelling. Characterisation of the coatings included microstructure evaluation, thermal conductivity and lifetime measurements. The modelling approach in combination with experiments undertaken in this study was shown to be an effective way to achieve coatings with optimised thermo-mechanical properties.

Keywords

Thermal barrier coatings, yttria-stabilised zirconia, OOF, microstructure, thermo-mechanical properties

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