Thermal diffusivity of plasma-sprayed Cr3C2-NiCr coatings

Thermal diffusivities of plasma-sprayed Cr3C2-NiCr coatings, deposited using three types of commercially available powders, were investigated using the laser-flash diffusivity method. Results indicate that the thermal diffusivities increase with increase in temperature for all coating samples, but the rate of increase is different in each case. At temperatures below 980 degrees C, the coating deposited using the coarse starting powder has the highest thermal diffusivity, while at temperatures above 980 degrees C, the coating deposited using the powder that contained the highest content of NiCr alloy has the highest thermal diffusivity. It is also evident that the thermal diffusivity in the cross-sectional direction is higher than that in the through-thickness direction. These results can be reasonably correlated, through a developed theoretical model, with the phases, microstructures, consisting of flat plate-like lamellae, pores, oxides, interlamellar and intralamellar cracks, and the formation of nanometer-sized grains in the coatings. (c) 2004 Elsevier B.V. All rights reserved.