MWCNTs Addition to Al2O3-SiC Binary Coating Deposited by Plasma Thermal Spray on Low Carbon Steel Substrate

Abstract

Coating with alumina and silicon carbide on low alloy steel specimens surface was conducted by using plasma thermal spray technique. The coating was of different percentages of alumina and silicon carbide (75% alumina +25% silicon carbide, 50% alumina + 50% silicon carbide) and then carbon nanotube was added to the mixtures of powder with percentage of 1%. Cyclic hot corrosion test was done after coating and XRD and SEM were performed to all samples after corrosion. Coating thickness was measured by SEM cross-section micrographs. The weight change of bare and coated specimens after 50 hours of corrosion in 67% wt. V2O5 + 33% wt. Na2SO4 at 950 °C was measured. The maximum reduction in weight was shown by specimens coated with 50% wt. alumina +50%wt. silica carbide with addition of 1% carbon nanotube . X-Ray of coated samples indicated that no phase change occurred to the coating materials. Scanning electron microscopy imaging of surface layer clarified that surface layer has relatively moderate porosity and some coating layers contain micro-cracks.