High temperature oxidation behavior and mechanism of a new Ni-Co-based superalloy. (July 2021)

• Record Type: Journal Article
• Authors: Zhuang, Xinpeng; Tan, Yi; You, Xiaogang; Li, Pengting; Zhao, Longhai; Cui, Chuanyong; Zhang, Huixing; Cui, Hongyang
• Is Part Of: Vacuum. Volume 189(2021)
• Publication Date: 2021-07
• Subjects: Ni-Co-based superalloy -- Oxidation behavior -- Oxide layer -- Oxidation mechanism; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2021.110219
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: The oxidation behavior and mechanism of a new Ni-Co-based superalloy developed for advanced engine turbine disks, were investigated at various temperature for different exposure times. The isothermal oxidation experiments, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and electron probe microanalysis (EPMA) were employed to analyze the oxidation characteristics of the new Ni-Co-based superalloy. The results show that the oxidation kinetics can be described by a parabolic law at each temperature and the oxidation rate constants K at temperature of 800 °C, 900 °C and 1000 °C are 0.015, 0.033 and 0.138 mg 2 cm −4 h −1, respectively. The oxidation process is controlled by out-diffusion of metallic elements and in-diffusion of oxygen. Multifarious oxides are formed on the surface of the alloy due to the complex alloying elements. The oxide scale is consisted of three parts: the external oxide layer containing TiO2 and a small amount of Cr2 O3 ; the middle oxide layer consisted of Cr2 O3, TiO2, Al2 O3 and the spinel phase; the internal oxide layer comprised of Al2 O3 . With further oxidation, TiO2 accumulates gradually on the external oxide layer because of the large diffusion distance of Ti, while O penetrated into the matrix can be captured by Al to prevent the further diffusion into alloy interior. Highlights: The oxidation behavior and mechanism of a new Ni-Co-based superalloy were firstly investigated. The first stage of oxidation process of the new Ni-Co-based superalloy obeys a parabolic law. The second stage still obeys a parabolic law, but the oxidation rate is decrease. The diffusion behavior and role of Ti during oxidation in the new Ni-Co-based superalloy were discussed.