Composition design, phase transitions of a new polycrystalline Ni-Cr-Co-W base superalloy and its isothermal oxidation dynamics behaviors at 1300°C

• Published in: Materials & design Vol. 129; pp. 26 - 33
• Main Authors: Zhang, Yubi, Hu, Xiaoyang, Li, Changrong, Xu, Weiwei, Zhao, Yongtao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05.09.2017
• Subjects: Composition design; Isothermal oxidation dynamics; Nickel base superalloy; Phase transition; Isothermal oxidation dynamics; Nickel base superalloy; Composition design; Phase transition
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2017.05.028

The composition, phase transitions and isothermal oxidation dynamics of a new polycrystalline Ni-Cr-Co-W base superalloy are investigated using CALculation of PHAse Diagrams (CALPHAD), Differential Scanning Calorimetry (DSC), ThermoGravimetric analysis (TG/dTG), Scanning Electron Microscope and Energy Dispersion Spectrum (SEM/EDS) methods. The microstructure of the designed alloy shows a uniform γ matrix with the precipitates of rich-Ti cellular η and rich-Nb acicular platelet δ phase, and no Topologically Close-packed Phases (TCPs) observed, and the oxide behavior obeys a parabolic law with a parabolic constant (kp) 2.945mg2/(cm4·h) at isothermal 1300°C for 30 hours. The oxide scales are composed of an outer loose oxide mixture containing Cr, Ni, Ti and Nb/Ta and generous pores presented for a volatilization of Cr2O3, and a dense aluminum-rich oxide layer. [Display omitted] •Designed compositions (wt%) of Ni-Cr-Co-W superalloy with Ni 57.5–63.5, Cr 18.0–20.0, Co 5.5–6.5, W 9.0–10.5 etc.•Microstructure exhibits a uniform γ matrix with some cellular rich-Ti η and acicular platelets rich-Nb δ precipitates.•Oxidation dynamics of the designed superalloy follows oxide parabolic law at the isothermal 1300oC for 30h in air.•Oxide scales are composed of an outer oxide mixture containing Cr, Ni, Ti, Nb/Ta and an inner aluminum-rich oxide layer.