Microstructure characterisation of un-melted particles in a plasma sprayed CoNiCrAlY coating

Research output: Journal PublicationArticlepeer-review

19 Citations (Scopus)

Abstract

Un-melted particles in thermally sprayed coatings are usually classified as impurity elements. Such impurities have a strong influence on the coating behaviour due to their different microstructural characteristics. In this work, the microstructural and mechanical characteristics of un-melted particles in a vacuum plasma sprayed CoNiCrAlY coating have been investigated. Microstructural analysis revealed the dendritic structure of the as-received powder and a spherical core inside the powder particle. The as-deposited coating comprised a dual phase structure of γ-Ni and β-NiAl, with coarse grains ranging 1–2 μm and fine grains ranging 500 nm or even less. Un-melted particles were found to exist in the coating after plasma spraying. The grain structure in the un-melted particles has not been fully developed, as characterised via electron backscattered diffraction (EBSD). It is shown that the spherical core in the initial powder was retained as un-melted particles due to insufficient melting during plasma spraying. In addition, a semi-continuous β-phase layer was found at the un-melted particle boundaries. Due to the inherently brittle nature of the β-phase layer and poor bonding at the particle boundaries, cracking along the un-melted particle boundaries occurred under compression.

Original languageEnglish
Pages (from-to)444-451
Number of pages8
JournalMaterials Characterization
Volume136
DOIs
Publication statusPublished - Feb 2018

Keywords

  • CoNiCrAlY coating
  • Cracking
  • Plasma spraying
  • Un-melted particles
  • β-phase

ASJC Scopus subject areas

  • Materials Science (all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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