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 °C in an argon atmosphere. SEM and XRD characterizations confirmed formation of SiC diffusion coating with about 500 μm 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 μm. Samples with single and dual layers were investigated in oxidation test at 1600 °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 °C were 29 wt.% and 2.4 wt.%, respectively.

► Formation of a dual-layer coating on the graphite. ► Developing graded SiC and nano SiC layers using pack cementation and electrophoretic deposition methods, respectively. ► Improvement of high temperature oxidation behavior of substrate. ► Weight loss of 29% and 2.4% for single layer coating of SiC and dual layer coating of SiCn/SiC, respectively.