Influence of embedded MoSi<sub>2</sub> particles on the high temperature thermal conductivity of SPS produced yttria-stabilised zirconia model thermal barrier coatings

Journal article (2016)

Authors

Justyna Kulczyk-Malecka The University of Manchester
Xun Zhang The University of Manchester
Philip J. Withers The University of Manchester
Ping Xiao The University of Manchester
James Carr The University of Manchester
A.L. Carabat (OLD) MSE-1
W.G. Sloof (OLD) MSE-1
S. van der Zwaag Novel Aerospace Materials - Aerospace Engineering
Federico Cernuschi RSE S.p.a.
Franck Nozahic ENSIACET
Daniel Monceau ENSIACET
Research Group
(OLD) MSE-1
Spark plasma sintering Self-healing materials Thermal barrier coatings Thermal conductivity
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Published Date

2016

Language

English

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Research Group

(OLD) MSE-1

Abstract

To prolong the lifetime of thermal barrier coatings (TBCs) recently a new method of microcrack healing has been developed, which relies on damage initiated thermal decomposition of embedded molybdenum disilicide (MoSi2) particles within the TBC matrix. While these MoSi2 particles have a beneficial effect on the structural stability of the TBC, the high thermal conductivity of MoSi2 may have an unfavourable but as yet unquantified impact on the thermal conductivity of the TBCs. In this work the thermal conductivity of spark plasma sintering (SPS) produced yttria-stabilised zirconia (YSZ) model thermal barrier coatings containing 10 or 20 vol.% of MoSi2 healing particles was investigated using the laser flash method. Measurements were performed on free-standing composite material over a temperature range from room temperature up to 1000 °C. Microstructural analysis was carried out by SEM combined with image analysis to determine the size, distribution and area fraction of healing particles. The measurements were compared with the results from microstructure-based multi-physics finite element (FE) models and analytical models (the asymmetric Bruggeman model and the Nielsen model) in order to study the effects of the addition of MoSi2 particles as well as the presence of micro-pores on the apparent thermal conductivity. The results show a strongly non-linear increase in the thermal conductivity of the composite material with the MoSi2 volume fraction and a dependence on the aspect ratio of MoSi2 particles. Interparticle connectivity is shown to play a big role too.