Evolution of oxides and their microstructures at 800°C in a γ-γ’ stabilised Co-Ni-Al-Mo-Ta superalloy

• DOI: 10.1016/j.corsci.2019.02.013
• Publication Date: 2019-04-18T03:12:20Z
• Authors: Saurabh Mohan Das; Mahander Pratap S...; Kamanio Chattopad...
• Keywords: 02 engineering and technology; 0210 nano-technology

Abstract The paper reports mechanism of high temperature oxidation of the new γ’-strengthened Co-30Ni-10Al-5Mo-2Ta (at%) alloy. The plots of mass gain vs. time show a parabolic growth behaviour at a temperature range of 650–800 °C. The cross-sections of the oxidised samples reveal formation of a complex multilayer of oxides. The top layer comprises of Co3O4 followed by a solid solution of (Co1-x,Nix)O (x varying from 0-0.2). A middle layer evolves with time comprising hexagonal molybdate Co2Mo3O8, metastable TaO and amorphous Al2O3. The γ’ dissolve near the interface exposing the γ solid solution with growth of amorphous Al2O3 along the grain boundary.