Effect of Laser Remelting on Hot Corrosion Behavior of Ni₃Al and Ni-20Cr Plasma-Sprayed Coatings

The hot corrosion behavior of Ni₃Al and Ni-20Cr plasma-sprayed coatings after laser remelting has been identified in a sodium sulfate-60% vanadium pentoxide (Na₂SO₄-60%V₂O₅) environment at 900°C under cyclic conditions. Complete areas were melted by making a series of parallel overlapping tracks using the 300-W Nd:YAG Laser at the Atomic Fuel Division (AFD), Bhabha Atomic Research Centre (BARC), Trombay, India. At the end of each cycle the samples were subjected to weight-change measurements after a visual examination. Finally the scale was analyzed using scanning electron microscopy/energy-dispersive x-ray analysis (SEM/EDAX) and electron probe microanalysis (EPMA) techniques. A slight improvement has been observed in the hot corrosion behavior after laser remelting for the Ni₃Al coating, whereas a slight decrease in the hot corrosion resistance of the Ni-20Cr coating after laser remelting has been experienced. The lower resistance to hot corrosion, as indicated by Ni₃Al coating, compared to that of Ni-20Cr may be due to the sulfidation of nickel.