Oxidation behavior and mechanism of porous nickel-based alloy between 850 and 1000 °C
(1. School of Aeronautics and Astronautics, Central South University, Changsha 410083, China;
2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
3. State Key Laboratory of Porous Metals Materials, Northwest Institute for Nonferrous Metal Research, Xi’an 710016, China;
4. Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522, Australia)
2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
3. State Key Laboratory of Porous Metals Materials, Northwest Institute for Nonferrous Metal Research, Xi’an 710016, China;
4. Institute for Superconducting and Electronic Materials, University of Wollongong, Wollongong, NSW 2522, Australia)
Abstract: 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 Cr2O3/NiCr2O4 and internal α-Al2O3 are formed on the surface of the oxidized porous alloys. γ？ phases favor the formation of NiO/Cr2O3/NiCr2O4 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.
Key words: porous alloy; high temperature oxidation; kinetics; oxide layer; diffusion