High temperature oxidation behaviour of NiCrAlY clad developed on SS-304 through microwave irradiation

Abstract

The current study investigates the underlying causes of the microstructural features, microhardness and high-temperature oxidation behaviour of the NiCrAlY powder cladded stainless steel (SS-304) substrate. The cladding was performed by utilizing an industrial multimode microwave apparatus, operating at 1.1 kW and 2.45 GHz with a 900 s processing time. The fabricated clad layer unveiled perfect metallurgical integration with the substrate and was noticed to be free from obvious flaws, including cracks or improper bonding at the clad-base material interface. The deposited clad layer revealed an equiaxed dendritic microstructure at the top while a typical columnar dendritic microstructure at the centre. The X-ray diffraction (XRD) examination of the clad sample revealed the existence of intermetallic compounds like γ′-Ni3Al, and Al5Y3O12 in addition to a solid solution of Iron (Fe) and Nickel (Ni) and chromium (Cr) enriched matrix. The microhardness of the clad layer was noticed to be higher than that of the uncladded SS-304 specimen. High-temperature oxidation investigation performed at 900 °C in air revealed weight gain by all the samples (bare and clad) in a parabolic fashion, initially for around 10 cycles of oxidation, beyond which the weight gain is noticed to saturate. The maximum oxidation resistance exhibited by the clad sample was credited with having intensified α-Al2O3 in the surface layer.