Investigation of SiC graded coating formation mechanism on graphite by pack cemetation process and influenece of types of raw material

structural materials. On the other hand, graphite can easily react with oxygen even at temperatures as low as 400 °C. The graded silicon carbide (SiC) characterized by compositional gradation over microsopic distances, is considered to be the most promising coating material. In this paper, the pack cementation technique was used to make a graded SiC coating on graphite at 1600°C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis display that the coating obtained by the pack cementation is a dense structure consisting α-SiC and β-SiC with functionally graded structure. the mechanism of formation of SiC coating on graphite is explained by thermodynamics analysis and chemical equilibrium calculations using HSC Chemistry software 6.0.The reaction-path mechanism indicates in the early stages of the process, SiO and CO gas species can be formed during Al2O3 reaction with Si and C and at two reaction Si=SiC and SiO(g)=SiC(g) can be considered as main reactions for SiC coating formation. It was found that the composition of raw materials has not marked effect on the microstructure and property of SiC coating. In fact, this paper proposes a method for the analysis and simulation of pack cementation reactions using HSC Chemistry software package. The results of the simulation are verified by experimental results.