Effects of pre-cracking on small punch creep testing of a vacuum plasma-sprayed CoNiCrAlY coating

H. Chen, T. H. Hyde, K. T. Voisey, D. G. McCartney

Research output: Journal PublicationArticlepeer-review

8 Citations (Scopus)

Abstract

This paper presents the results of small punch creep testing (SPCT) of a vacuum plasma-sprayed (VPS) CoNiCrAlY coating (Co – 31.7%, Ni – 20.8%, Cr – 8.1%, Al – 0.5%, Y, all in wt%) carried out at 750 ℃. Coating cross-sections, after initial heat treatment, after sample clamping in the test rig prior to testing and after SPCT, were examined using scanning electron microscopy (SEM). A dual phase structure consisting of a fcc γ-Ni matrix and a bcc β-NiAl secondary phase was found to exist. A large number of partially melted powder particles, with a semi-continuous β layer surrounding most of the partially melted particles, were found in the coating. Pre-cracking was observed to occur around the partially melted particles after sample clamping was applied in the test rig prior to testing. This was due to the inherent brittleness of the β layer around those particles. Very short failure times were obtained from the SPCT of the specific VPS CoNiCrAlY coatings, due to the pre-existing cracks formed during sample clamping.

Original languageEnglish
Pages (from-to)242-249
Number of pages8
JournalProceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications
Volume232
Issue number3
DOIs
Publication statusPublished - 1 Mar 2018

Keywords

  • creep
  • failure
  • pre-cracking
  • Small punch creep test
  • VPS coating

ASJC Scopus subject areas

  • General Materials Science
  • Mechanical Engineering

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