Hot corrosion behavior of HVAF-sprayed NiCrAlY coatings: Effect of surface modification

NiCrAlY coatings have been widely used for the protection of hot component against high temperature oxidation and hot corrosion in industrial gas turbines. Surface treatment on high velocity air-fuel (HVAF) sprayed NiCrAlY coating improves oxidation resistance of coating by fast formation of a uniform alumina scale with a considerably lower growth rate compared to the as-sprayed coatings. However, the influence of such treatment on hot corrosion behavior of HVAF sprayed NiCrAlY coating has been rarely discussed. The aim of this work is to identify the surface treatment effect on hot corrosion resistance of HVAF sprayed NiCrAlY coatings. Specimens treated in different ways (ground, polished) was tested in a molten salt (75 wt.% Na2SO4 + 25 wt.% NaCl) environment at 900 ⁰C. Characterization of the coating surface scales and microstructures were performed using X-Ray diffraction and Scanning Electron Microscopy. The surface treatment effects on corrosion resistance of HVAF-sprayed NiCrAlY coatings are discussed.