Oxidation Behavior and Interfacial Bonding Properties of NiCrAl Alloys

Abstract

AbstractThe oxidation behavior and oxidation kinetics of NiCrAl alloy were studied by XRD, SEM and the thermogravimetric analysis method. The adhesion strength of the films was characterized by micron scratch tester. The results show that the oxide film has not formed at 600 °C and 700 °C, and an oxide layer of Al2O3 has formed at 800 °C. Moreover, an oxide layer composed of Cr2O3 and Al2O3 has formed at 900 °C. After oxidation at 800 °C for 100 h, partial θ‐Al2O3 has transformed to steady‐state α‐Al2O3 and a dense oxide film of Al2O3 with the thickness of about 620 nm has formed on the surface of the NiCrAl alloy. The oxidation kinetics curve of the alloy obeys the parabolic law and there are two oxidation rate constants in the oxidation process. The oxidation rate constant of 1.58×10−4 mg2⋅cm−4⋅h−1 in the early oxidation period (0∼12 h) and the oxidation rate constant of 1.04×10−4 mg2⋅cm−4⋅h−1 in the late oxidation period (12∼100 h) indicate that the oxidation resistance ability of the alloy increases with the extension of oxidation time. With the increase of the oxidation time, the interface bonding strength between the oxide film and the substrate can be improved and reaches 5.21 N at 800 °C for 100 h.