Comparative High Temperature Oxidation Behaviour of Ni-20Cr Coating Deposited by High-Velocity-Oxy-Fuel and Detonation Gun Spray Techniques

In this study, High velocity oxy fuel (HVOF) spray and Detonation gun (D-Gun) spray techniques were used to deposit Ni-20Cr coatings on a commonly used boiler steel ASTM SA213-T-22. The specimens with and without coatings were subjected to cyclic oxidation testing at an elevated temperature of 900°C to ascertain their oxidation behaviours. Mass change data  was recorded to formulate the kinetics of oxidation for the specimens. The exposed specimens were characterized by X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). The uncoated sample suffered intensive spallation and mass gain. It was observed that the oxidation rate was appreciably reduced in terms of mass gain after the application of the both thermal sprayed Ni-20 Cr coatings .The HVOF spray Ni-20Crcoating showed a better oxidation resistance in comparison with the D-gun spray Ni-20Cr coating.