Formation of Carbide Layer on Carbon Materials by Silicon and Chromium Impregnation

Abstract

The metal carbide layer on the surface of the carbon substrates was prepared by silicon and chromium impregnation. The effect of the porosities and impurities of the carbon substrates on the formation of the metal carbide layer was investigated. (1) In the substrates reacted with Cr powder at 1450°C for 3h, the chromium carbide layer formed on the surface of the substrates with a porosity of 18 % was confirmed to be a Cr23C6 phase. On the surface of the substrates with a porosity of 10 %, the formation of a Cr7C3 phase was found. The thickness of the chromiumcarbide layer increased with an increase of the reaction time. No effect of the impurities on the formation and the thicknessof chromium carbide layer was observed. (2) The formation rate of SiC on the substrates increased with increasing the reaction time. In the heattreatment in Si powder at 1450°C for 3h, the formation rate of SiC on the surface of the substrates with a porosity of 18 % was higher than that on the surface of the substrates with a porosity of 10 %. And also, the formation of SiC in the substrates was observed; the concentration of SiC along the thickness decreased rapidly up to 0.3mm and then gradually in a range 0.3-1.0mm. No influence of impurities containing in the substrates was found on the formation of SiC on and in the substrates.