Effects of initial oxidation on β phase depletion and oxidation of CoNiCrAlY bond coatings fabricated by warm spray and HVOF processes

Takeru Mori, Seiji Kuroda, Hideyuki Murakami, Hiroshi Katanoda, Yukihiro Sakamoto, Scott Newman

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

Thermal barrier coatings (TBC) have been applied extensively onto the high-temperature components in turbine engines to prolong their service life in extremely harsh environments. TBCs are typically composed of a ceramic top coating for thermal insulation and a metallic bond coating (BC) for oxidation resistance and providing adhesion to the top coating. MCrAlY, where M stands for Co, Ni or an alloy of these elements, is a widely used material for BC and usually produced by low pressure plasma spraying (LPPS) in industry. Recently high velocity oxy-fuel (HVOF) spraying is attracting significant attention as a more economical alternative procedure to LPPS. In terms of the quality of sprayed coatings, however, LPPS is still superior in terms of oxygen pick-up during coating preparation, which should affect the performance as a bond coating in service. In this study, a modified HVOF process, so called 2-stage HVOF or warm spray (WS) was applied to deposit a CoNiCrAlY alloy. Comparisons between BCs fabricated by HVOF and WS were made in terms of microstructure, surface morphology, and cyclic and isothermal oxidation behaviors in air at 1423. K up to 100. cycles and 100. h respectively. The results showed that rougher and less oxidized BCs were deposited by the WS process, which exhibited slower kinetics of β-phase depletion during oxidation. A simple Al diffusion model revealed that apparently a small difference in the initial oxidation between the two spraying processes had significant influence on the β-depletion phenomena, which may influence the life time as a bond coating.

Original languageEnglish
Pages (from-to)59-69
Number of pages11
JournalSurface and Coatings Technology
Volume221
DOIs
Publication statusPublished - 2013 Apr 25

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Keywords

  • Diffusion
  • MCrAlY
  • Phase diagram
  • Surface roughness
  • Thermal barrier coating

ASJC Scopus subject areas

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

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