Research Paper

Microstructure and High Temperature Oxidation Resistance of Si-Y2O3 Co-deposition Coatings Prepared on Nb-silicide-based Ultrahigh Temperature Alloy by Pack Cementation Process

  • QI Tao ,
  • GUO Xi-Ping
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  • (State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China)

Received date: 2009-03-04

  Revised date: 2009-04-14

  Online published: 2010-04-22

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℃, 1150℃ and 1250℃, 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℃ 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℃ is composed of TiO2, SiO2 and Cr2O3. Si-Y2O3 co-deposition coatings possess better oxidation resistance than simple Si deposition coatings.

Cite this article

QI Tao , GUO Xi-Ping . Microstructure and High Temperature Oxidation Resistance of Si-Y2O3 Co-deposition Coatings Prepared on Nb-silicide-based Ultrahigh Temperature Alloy by Pack Cementation Process[J]. Journal of Inorganic Materials, 2009 , 24(6) : 1219 -1225 . DOI: 10.3724/SP.J.1077.2009.01219

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