Hot corrosion of the ceramic composite coating Ni3Al–Al2O3–Al2O3/MgO plasma sprayed on 316L stainless steel

Abstract Ni 3 Al–Al 2 O 3 –Al 2 O 3 /MgO three-layered coatings with thicknesses of 50, 100, and 150 μm for Al 2 O 3 /MgO and 100 μm for the other layers were deposited on 316L stainless steel using plasma spraying. X-ray diffraction, atomic force microscopy, furnace hot corrosion testing in the presence of a mixture of Na 2 SO 4 and V 2 O 5 corrosive salts and scanning electron microscopy were used to determine the structural, morphological and hot corrosion resistance of samples. Results revealed that the crystalline grains of MgO and Al 2 O 3 coating were very small. Weight loss due to hot corrosion decreased from approximately 4.267 g for 316L stainless steel without coating to 2.058 g. The samples with 150 μm outer coating showed improved resistance with the increase in outer layer thickness. Scanning electron microscopy of the coated surface revealed that the coating's resistance to hot corrosion is related to the thickness and the grain size of Al 2 O 3 /MgO coatings.