High-Temperature Erosion-Corrosion Performance of High-Velocity Oxy-Fuel Sprayed Ni-20 Cr Coating in Actual Boiler Environment |
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Authors: | G Kaushal H Singh S Prakash |
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Affiliation: | (1) RIMT–Institute of Engineering and Technology, Mandi Gobindgarh, 147301, Punjab, India;(2) Indian Institute of Technology Ropar, Roopnagar, 140001, Punjab, India;(3) Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India; |
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Abstract: | The high-velocity oxy-fuel (HVOF) spray technique was used to deposit Ni-20Cr coating on a commonly used boiler steel ASTM
A213 347H. The specimens with and without coating were exposed to the super heater zone of a thermal power plant boiler at
a temperature of 973 K (700 °C) under cyclic conditions to ascertain their erosion-corrosion (E-C) behavior. High-temperature
oxidation behavior of the specimens was also evaluated under cyclic thermal loading conditions at an elevated temperature
of 1173 K (900 °C). Mass change data and thickness loss were measured to formulate the kinetics of E-C/oxidation for the specimens.
The exposed specimens were characterized by X-ray diffraction (XRD) and field emission–scanning electron microscopy/energy
dispersive spectroscopy (FE-SEM/EDS). The uncoated steel suffered higher E-C in comparison with its coated counterpart in
terms of mass loss as well as thickness loss. It was observed that overall mass loss was reduced by 31 pct and thickness loss
by 44 pct after the application of the coating. The possible formation of Cr2O3 phase in the coated substrate may be suggested to contribute to better E-C behavior. During air oxidation exposures, the
coating was found to be intact with only marginal spallation of its oxide scales, which is an indicator of good adhesion between
the coating and substrate steel. The air oxidation mass change data indicated that the coating enhanced the oxidation resistance
of the steel by 85 pct. |
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