Microstructure and high temperature oxidation resistance of Si-Y2O3 co-deposition coatings prepared on Nb-silicide-based ultrahigh temperature alloy by pack cementation process

Tao Qi, Xi Ping Guo

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25 Scopus citations

Abstract

Si-Y2O3 co-deposition coatings on Nb-silicide-based ultrahigh temperature alloy were prepared by pack cementation processes. The co-deposition holding temperatures were 1050°C, 1150°C and 1250°C, and the holding times were 5, 10, 15 and 20h, respectively. The microstructure and isothermal oxidation resistance of the coatings were studied. The results show that all Si-Y2O3 co-deposition coatings are composed of a (Nb,X)Si2 (X represents Ti, Hf and Cr elements) outer layer and a (Nb,X)5Si3 transitional layer. Some thin discontinuous (Cr,Al)2(Nb,Ti) laves phase precipitates exist between the substrate and (Nb,X)5Si3 transitional layer. EDS analyses reveal that the distribution of Y on the coatings is not uniform. The content of Y in (Nb,X)Si2 and (Nb,X)5Si3 phases is about 0.46at%-0.57at% while that in (Cr,Al)2(Nb,Ti) is about 0.94at%. After oxidation at 1250°C for 5, 10, 20, 50 and 100h respectively, the retained Si-Y2O3 co-deposition coatings still possess double layers structure with their original constituent phases and combine tightly with both scale and substrate. The dense scale developed on Si-Y2O3 co-deposition coatings during oxidation at 1250°C is composed of TiO2, SiO2 and Cr2O3. Si-Y2O3 co-deposition coatings possess better oxidation resistance than simple Si deposition coatings.

Original languageEnglish
Pages (from-to)1219-1225
Number of pages7
JournalWuji Cailiao Xuebao/Journal of Inorganic Materials
Volume24
Issue number6
DOIs
StatePublished - Nov 2009

Keywords

  • Coating structure
  • High temperature oxidation resistance
  • Nb-silicide-based ultrahigh temperature alloy
  • Si-YO co-deposition coatings

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