High temperature oxidation behavior of y'-strengthened CoNi-base superalloys

Oxidation behavior of y'-strengthened CoNi-base superalloys was investigated with isothermal oxidation tests conducted in air at 800 and 900 degrees C, respectively, for 100 h. It is observed that both 30Ni-10Al-4W-4Ti-2Ta (4W2Ta) and 30Ni-10Al-5W-4Ti-1Ta (5W1Ta) alloys exhibit a three-layered oxide scale structure after oxidation. Addition of Ta increases oxidation mass gain of CoNi-based high-temperature alloys, but the effects on the type and distribution of oxidation products are not significant. However, the oxidation temperature has a great influence on oxide surface morphology and oxidation mechanisms for those two alloys. After oxidation at 800 degrees C, the outermost oxide film contains Co3O4, CoO, and NiO, and when the oxidation temperature is 900 degrees C, the outermost oxide film contains only CoO. (c) 2024 The Authors. Published by Elsevier B.V. on behalf of Institute of Metal Research, Chinese Academy of Sciences. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)