Microstructure and thermophysical properties of as-cast CoNiCrAl bond coat alloys at different Al contents

H. Chen, L. Li, R. Yang, W. Zhu, A. Rushworth, Y. Yin, X. Wang

Research output: Journal PublicationArticlepeer-review

1 Citation (Scopus)

Abstract

In this paper, the microstructure and thermophysical properties of two CoNiCrAl bond coat alloys with differing Al contents were investigated. Two CoNiCrAl alloys with compositions of Co-31.7%Ni-20.8Cr-10Al and Co-31.7%Ni-20.8Cr-12Al (all in wt%) were prepared by vacuum induction melting and casting. The microstructure of the as-cast CoNiCrAl alloys was characterised by scanning electron microscopy (SEM), X-ray diffractometry (XRD), energy dispersive spectroscopy (EDS) and electron backscattered diffraction (EBSD). The phase changes of the CoNiCrAl alloys as a function of temperature were studied by differential scanning calorimetry (DSC). Thermophysical properties such as thermal conductivity, thermal diffusivity and thermal expansion were evaluated. The as-cast CoNiCrAl alloys exhibited a two-phase structure, consisting of the Al-rich BCC β phase and Co and Ni-rich FCC γ phase. It was found that the β-phase fraction increased with the overall Al content in the alloy. A two-stage thermal expansion was noted for both CoNiCrAl alloys. In addition, it was shown that the CoNiCrAl alloy with the higher Al content exhibited a lower thermal expansion coefficient at high temperatures. This is because more β phase was formed in the CoNiCrAl-12 alloy, resulting in a reduced thermal expansion coefficient.

Original languageEnglish
Article number165575
JournalJournal of Alloys and Compounds
Volume918
DOIs
Publication statusPublished - 15 Oct 2022

Keywords

  • CoNiCrAlY bond coat
  • Microstructure
  • Phase distribution
  • Thermophysical properties
  • β-phase

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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