Synthesis of an oxidation-resistant SiC coating on graphite and modeling analysis with thermodynamics calculations

Abstract

AbstractA graded SiC coating was prepared on a graphite substrate by a pack cementation technique at 1 873 K to improve the oxidation resistance. The HSC Chemistry software was used for thermodynamics calculations. The coating was characterized by means of X-ray diffraction and scanning electron microscopy. Isothermal oxidation testing of the samples was performed at 1 773 K in air. The modeling analysis indicated that aluminum oxide can be reduced and an SiC coating can be formed due to the reaction of silicon with CO and carbon with SiO. The growth of the SiC nanofibers was attributed to the gaseous reaction of SiO with CO. A 600 μm thick SiC layer can be observed at the graphite–coating interface. The simulation and experimental results were consistent with each other. The mass loss of the SiC coated sample was 1.1 % after oxidation for 10 h, whereas the graphite was fully oxidized after 1 h.