Thermal conductivity of plasma-sprayed W/SiC composite for high-temperature energy applications

摘要

W/SiC metal matrix composites were produced by gas tunnel type plasma spraying (GTPS) using a mixture of 12 wt.% SiC - 88 wt.% W feedstock powder. This work aimed at the optimization of the plasma gun current for deposition of a W/SiC composite with fine microstructure on AISI 304 substrate. Characterization of deposits was performed in order to assess microstructure, micro-hardness, thermal diffusivity and thermal conductivity. WO3 was detected in the composite deposits, which indicated that the tungsten partially oxidized during plasma spraying. Also, the deposit composite was dense and nearly free of pores due to the little mismatch between the coefficient of thermal expansion (CTE) for W and SiC. Microhardness values gradually decreased as a function of input current due to the formation of WO3 and the decomposition of SiC particles in high temperature flame region. The thermal conductivity as high as similar to 59W/mK was obtained at gun current 80 A. It was found that both tungsten oxide and structure imperfections have a significant influence on the thermal conductivity and mechanical properties. (c) 2007 Elsevier B.V. All rights reserved.