Correlation of Measured Thermal Conductivity to a Functionally Graded Material's Microstructure

Abstract

<jats:p>Functionally Graded Materials (FGMs) are used in a number of applications as a protective barrier to extreme environments. One such application of FGMs is to protect metal parts from high temperature environments. FGM coatings are plasma spray deposited onto surfaces of both simple and complex machined parts. Knowing the thermal conductivity of the FGM coating allows engineers to effectively develop high temperature designs with accurate estimates of heat transfer and thermal loading.</jats:p><jats:p>In this study, a FGM made by Caterpillar, USA, was measured with our steady state thermal conductivity measurement apparatus. The sample measured is a 10 layer graded coating using a Metro<jats:sup>*</jats:sup> 461 bond coan<jats:sup>4</jats:sup> to a Metco<jats:sup>*</jats:sup> 205 ceria-yittria stabilized zirconia, with a Ni-Co-Cr-Al-Y metal grading. Figure 1 shows a plot of the thermal conductivity (W/m<jats:sup>*</jats:sup>K) as a function of temperature (K) for this material. The sudden drop in thermal conductivity at approximately 1073K was totally unexpected</jats:p>