Effect of thermal spray coating cermets on superalloy to combat hot corrosion

Abstract

Burning coal emits contaminant gases that come into contact with turbine parts and speed up hot corrosion. To overcome the corrosion effect, it is necessary to opt for thermal spray coatings that offer resistance to hot corrosion. In the current study, hot corrosion investigations were done on both uncoated and high‐velocity oxygen fuel spray‐coated Superco‐650 alloys at 700°C for 50 cycles, in Na2SO4 + 60% V2O5 salt environment. At the end of each cycle, the weight gains or loss was recorded. We used powder X‐ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy (EDS) to examine the hot corrosion impact. Our finding demonstrated that the uncoated Superco‐605 alloy was subjected to extensive spallation in the form of oxide scale remgoval due to the formation of an unprotected Fe2O3 oxide phase. Contrarily the coated Superco‐605 alloy gained less weight, and the oxide scales remained undamaged. The nickel, chromium oxides, and their sulfide phases were revealed by the EDS examination of the oxide scale over the coated sample, which is presumed to offer resistance to high‐temperature corrosion effects.