Oxidation behavior and mechanism of porous nickel-based alloy between 850 and 1000 °C
The oxidation behavior and mechanism of a porous Ni-Cr-Al-Fe alloy in the temperature range from 850 to 1000 °C were investigated by optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) analyses and X-ray photoelectron spectroscopy (XPS). The results show that the oxidation kinetics at 950 and 1000 °C of this porous alloy is pseudo-parabolic type. Complex layers composed of external Cr 2 O 3 /NiCr 2 O 4 and internal α-Al 2 O 3 are formed on the surface of the oxidized porous alloys. γ' phases favor the formation of NiO/Cr 2 O 3 /NiCr 2 O 4 during the initial oxidation. Many fast diffusion paths contribute to the development of the oxide layers. The decrease of the open porosity and the permeability with exposure time extending and temperature increasing can be controlled within a certain range.