Microstructure, Mechanical and Thermal Properties of Plasma- Sprayed W/SiC Metal Matrix Composite Coating
FAHIM F. Narges, KOBAYASHI Akira
Transactions of JWRI
abstract:A functionally graded SiC/W metal matrix composite (MMC) has been successfully produced by gas tunnel type plasma spraying. The starting powder was a mixture of 12% W and 88 wt% SiC. The effect of plasma gun current on the microstructure, mechanical and thermal conductivity properties was investigated. The results revealed that the reaction phases, namely tungsten silicides (WSi2, W5Si3) and tungsten carbides (WC, W2C), were not formed in various processing conditions. The presence of WO3 was detected in the composite deposits, which indicated that the tungsten partially oxidized during plasma spraying. Also, the composite deposited was dense and nearly free of pores due to the small mismatch between the coefficients 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 the high temperature flame region. A thermal conductivity as high as ~ 59 W/m.K was obtained. It was found that both tungsten oxide and structure imperfections have a significant influence on the thermal conductivity and mechanical properties.
keywords:(Microstructure); (Gas tunnel type plasma spraying); (Abrasive Wear); (W/SiC Metal-Matrix Composite); (Microhardness); (Thermal Diffusivity); (Thermal Conductivity)
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