Nano-SiC/SiC anti-oxidant coating on the surface of graphite

In this research, a dual-layer coating has been used to improve high temperature oxidation resistance of graphite substrate. For first layer, silicon carbide was applied by pack cementation method. Powder pack consisted of Si, SiC and Al2O3 and heat-treated at 1650 degrees C in an argon atmosphere. SEM and XRD characterizations confirmed formation of SiC diffusion coating with about 500 mu m including compositionally gradient of C and Si elements. Electrophoretic deposition (EPD) was used to deposit nano SiC (SiCn) particles as second layer. Thickness of second layer of SiCn in corresponded optimal situation was 50 mu m. Samples with single and dual layers were investigated in oxidation test at 1600 degrees C. Results showed that an extreme increase was occurred in oxidation resistance after application of second layer of nano SiC. Weight loss value for single layer coating of SiC and dual layer coating of SiCn/SiC after oxidation test for 28 h at 1600 degrees C were 29 wt.% and 2.4 wt.%, respectively. (C) 2012 Elsevier B.V. All rights reserved.