Evaluation of the ductile-to-brittle transition temperature in a thermally sprayed CoNiCrAlY coating by small punch multi-step loading tests

H. Chen, J. Yang, X. L. Xiao

Research output: Journal PublicationArticlepeer-review

2 Citations (Scopus)

Abstract

High velocity oxy-fuel thermal spraying was used to prepare free-standing CoNiCrAlY (Co-31.7%Ni-20.8%Cr-8.1%Al-0.5%Y, all in wt%) coatings of an approximate thickness of 0.5 mm. Small punch tests under multi-step loading conditions were performed between room temperature and 600 ° C on these samples to evaluate the ductile-to-brittle transition temperature. The microstructure of the coatings was characterised using a scanning electron microscope with energy-dispersive X-ray analysis. A two-phase structure consisting of fcc γ-Ni and bcc β-NiAl was found to exist. The displacements obtained from small punch multi-step loading tests at each load increment were relatively small and similar at temperatures below 500 ° C but a significant increase in displacement was noted at 600 ° C. Fractographic investigation showed that the main fracture mode was dominated by extensive γ matrix tearing at elevated temperatures. A distinct stress and strain behaviour was found at 600 ° C, indicating that the ductile-to-brittle transition temperature of this CoNiCrAlY coating occurred between 500 ° C and 600 ° C.

Original languageEnglish
Pages (from-to)6-13
Number of pages8
JournalProceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications
Volume231
Issue number1-2
DOIs
Publication statusPublished - 1 Feb 2017

Keywords

  • MCrAlY coating
  • Small punch test
  • ductile-to-brittle transition temperature
  • high velocity oxy-fuel spraying
  • strain

ASJC Scopus subject areas

  • General Materials Science
  • Mechanical Engineering

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