Thermal resistance and apparent thermal conductivity of thin plasma-sprayed mullite coatings

A transient comparative exponential method (CEM) was developed to measure the thermal conductivity of thin ceramic coatings based on comparing the rate of heating during its exponential stage of a metal specimen with known thermal capacity without and with a coating. The experimental results were explained based on modelling the conductive heat transfer within the plasma-sprayed porous coating structure taking into account the contact heat barrier resistance (CHBR) between splat boundaries, and between substrate and coating as well as their dependence on the gas pressure within pores and microcracks as a function of the geometric altitude.