Evaluation of continuous oxidation behavior plasma spraying of SiC/Mo-Si-B on graphite

This study was conducted to evaluate the adhesion strength and oxidation behavior of SiC/Mo-Si-B coating applied on graphite substrates. For this purpose, SiC coating was created on graphite substrate using pack cementation method with NH4Cl activator. The secondary layer Mo-Si-B coating was created using atmospheric plasma spraying (APS) with argon protective shower on the samples. Surface morphology and chemical composition of the SiC and Mo-Si-B coatings were inve stigated by Scanning Electron Microscopy (SEM) equipped with an Energy Dispersive Spectroscopy (EDS) system. Surface analysis by X-ray diffraction (XRD) revealed that the structure of SiC was mainly composed of SiC phase. In the case of Mo-Si-B, different phases of Mo and Si, Mo and B, and pure Mo were identified. The adhesion of the multi-layer coating was evaluated by tensile test which indicated a sufficient adhesion and cohesion of the coating. The oxidation test was carried out in the air at 1273 K and the time and weight changes were recorded simultaneously. The results showed that the applied coating significantly improves oxidation resistance of graphite with SiO2 and B2O3 glass layers.