Analysis of carbide transformation in MC-M23C6 and its effect on mechanical properties of Ni-based superalloy

Xiaoqing Song, Yongxin Wang, Xiaoxiao Zhao, Jing Zhang, Yan Li, Yifan Wang, Zheng Chen

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48 Scopus citations

Abstract

An investigation based on electron microscopy and crystallographic analysis was employed to gain insights into the carbide transformation in MC-M23C6 complex carbide of Haynes282; nanoindentation test and first-principles calculations were performed to study its effect on mechanical properties of the alloy. The results show that MC(M=Ti, Mo)-M23C6(M=Cr, Mo) complex carbide, which exhibits as bull's eye structure, shows an orientation relationship of (131̅)MC//(4̅20)M23C6, [11̅2̅]MC//[123]M23C6. Besides, intermediate phase M2C forms at partial MC/M23C6 interface. During creep, Cr diffuses from M23C6 to MC and substitutes Ti under the driving force of concentration gradient. The substitution induces thermal expansion anisotropy in polyhedral clusters of MC, which will trigger the flipping of diagonals and transform MC into M23C6 through the transformation of coordination polyhedron of C atoms from octahedron to twisted cube. The hybridizations, especially the low-energy hybridizations, between C-p, Ni-d, Cr-d and Ti-d orbitals of the atoms located at M23C6/Ni and M23C6/MC interfaces make great contribution to the plentiful chemical bonds formed at the interfaces. These chemical bonds result in the high bonding strength of the two interfaces and thus the beneficial effects of the MC-M23C6 carbides on mechanical properties of the alloy. Moreover, nanoindentation test indicates that MC-M23C6 carbides do a better job of strengthening than individual MC or M23C6 carbide. Therefore, the transformation from MC to M23C6 is detrimental to the mechanical properties of the alloy. The demonstrated concept shed light on the rational design of higher property superalloys for various potential applications.

Original languageEnglish
Article number164959
JournalJournal of Alloys and Compounds
Volume911
DOIs
StatePublished - 5 Aug 2022

Keywords

  • Carbide transformation
  • Crystallographic analysis
  • First-principles calculation
  • Nanoindentation
  • Superalloy

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