Microstructure and Oxidation of NiCr Alloys Studied by Analytical In Situ Environmental TEM

Abstract

NiCr alloys are basic and model alloys for many industrial applications in airplane engines, including Ni-based superalloys. Proper Cr content are decisive for alloys’ environmental applications for corrosive consideration. The microstructure and oxidation properties from the bulk material to the atomic scale of NiCr alloys with different Cr contents from 10 to 50 at.% were systematically studied in this work. The oxidation mechanism in NiCr alloys with different Cr contents was analysed by analytical in situ environmental transmission electron microscopy. The increased porosity of the NiO/NiCr₂O₄ oxide layer in the 10 at.% Cr-containing alloy seriously decreases its oxidation resistance, and Cr contents between 20 and 40 at.% offer outstanding oxidation resistance due to the inhibited growth of NiO/NiCr₂O₄ oxides. A high quantity of phase boundaries with a high Cr content of 50 at.% exhibit poor corrosion resistance due to short-circuit oxidation paths by its FCC/BCC dual-phase structure.

Keywords: Oxidation, NiCr alloy, Chromium, In situ, Transmission electron microscope