Improving hot corrosion resistance of Cr₃C₂–20NiCr coatings with CNT reinforcements

Abstract

Carbon Nanotubes (CNT) reinforced Cr 3 C 2 -20NiCr composite coatings were prepared and deposited on alloy steel using high-velocity oxyfuel (HVOF) thermal spraying method. The comparative effects of variation in CNT content (from 1 to 2 weight percentage) on mechanical properties and hot corrosion behaviour in super-heater zone of actual coal-fired boiler of a thermal power plant at 900°C have been investigated. After exposure to boiler environment, the corrosion products have been analysed by thermogravimetric analysis, Xray diffraction, scanning electron microscopy, energy dispersive and cross-sectional analysis techniques. The results confirmed that variation in CNT content improved the mechanical and microstructural properties of surface coatings by modifying their surface characteristics. The variation in CNT content improved the corrosion protection property of composite coating at high temperature of exposure. Reduction in corrosion rate was observed with increase in CNT content from 1 to 2 weight percentage in the Cr 3 C 2 -20NiCr coating matrix.

Effect of nano yttria-stabilized zirconia on properties of Ni-20Cr composite coatings

“…The presence of Fe and Mn in the Ni-20Cr conventional coating was found by EDS analysis, which could be attributable to Fe and Mn migration from the substrate to the coating matrix due to porosity in conventional coating. Diffusion of base elements through pores/voids in the coating matrix has also been reported by various authors [32][33][34][35]. Reinforcement of nano YSZ particles in Cr3C2-25NiCr coating filled the gaps, reducing porosity which prevents diffusion of base elements to the coating matrix, thereby increasing the microhardness of the coatings.…”

Development of CNT reinforced Al2O3-TiO2 coatings for boiler tubes to improve hot corrosion resistance

“…CNTs are responsible for reduced porosity and improved adhesion, which further decrease the corrosion rate [7,9]. A number of researchers [15,16] have reported similar findings in their studies on carbon nanotubes.…”

“…This ash contains K2O and Na2O and reacts with boilers flue gases (SO2, SO3 and O2). The authors [13][14][15][16] reported that this content of ash was rendered because of coal burning. Deposition of such low melting-point elements initiates hot corrosion on the boiler tube surface [17].…”

Hot corrosion behaviour of CNT-reinforced ZrO2-Y2O3 composite coatings on boiler tube steel at 900°C

“…A hot corrosion cycle composed of heating the test specimen for 1-h exposure in the furnace followed by 20 min of cooling to room temperature. The cyclic tests were performed to simulate an actual boiler environment (Goyal, 2018b; Goyal et al , 2017; Rani et al , 2017; Goyal and Goyal, 2020). The weight of each specimen along with the alumina boat was measured carefully on digital weighing machine after every cycle.…”