Formation and subsequent phase evolution of metastable Ti-Al alloy coatings by kinetic spraying of gas atomized powders

M. Gizynski, S. Miyazaki, J. Sienkiewicz, S. Kuroda, H. Araki, H. Murakami, Z. Pakiela, Atsushi Yumoto

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

High temperature application of modern Ti-alloys is often limited by their insufficient oxidation resistance at temperatures exceeding 650 °C. One way to overcome this obstacle is application of an overlay coating made of TiAl-based alloys. In this study kinetically sprayed coatings of Ti-46Al-8.5Nb-1Ta (at%) on a commercial alloy IMI-834 were investigated. The feedstock powder fabricated by gas atomization consisted of non-equilibrium α-Ti and β-Ti phases. Heat treatment of the powder at 750 °C triggered transformation to the equilibrium ordered γ-TiAl and α2-Ti3Al phases. Mechanical properties of both the as-atomized and the heat treated powders were tested, showing that the as-sprayed one possesses lower hardness and higher ductility. Since such properties of the as-atomized powder are more suited for kinetic spraying, the as-atomized powder was used for coating fabrication. The as-sprayed coatings inherited the non-equilibrium phases of the atomized powder with significant deformation. The coatings were annealed at 750 °C and immediate transformation to a refined microstructure containing the γ-TiAl and α2-Ti3Al phases was observed in < 20 min. Longer annealing time resulted in significant grain growth and formation of defect-free grains.

Original languageEnglish
Pages (from-to)240-249
Number of pages10
JournalSurface and Coatings Technology
Volume315
DOIs
Publication statusPublished - 2017 Apr 15

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Keywords

  • Coating
  • Intermetallics
  • Kinetic spraying
  • Phase transformation
  • Titanium aluminides

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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