Oxidation behaviour of Nimonic 263 in high-temperature supercritical water

ABSTRACT

The oxidation tests of the Nimonic 263 alloy exposed to deaerated supercritical water at 600–700°C under 25 MPa were carried out for up to 1000 h. Oxidation rate increased with an increase in temperature. The microstructure and phase composition of oxide scale were analysed by scanning electron microscopy/energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. It can be seen that a complex oxide structure formed on the surface of Nimonic 263 including an outer layer of Ni–Fe/Ni–Cr spinel oxide, Ni/Co hydroxide and TiO₂ and an inner layer of a mixture of NiCr₂O₄ and Cr₂O₃ while the innermost layer is made up of Cr₂O₃. The MoO₃ can be observed at 600°C but disappeared with the increasing temperature. The growth mechanism of oxide scale was discussed.

KEYWORDS:

• Ni-base alloy
• oxidation
• supercritical water
• temperature

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by National Natural Science Foundation of China: [Grant Number 51471069]; Natural Science Foundation of Beijing: [Grant Number 2152029]; Science and Technology Program of Beijing (Z181100005218006).