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Phase Constitution and Oxidation Resistance of B2 (Ir, Co)Al

Published online by Cambridge University Press:  11 February 2011

Hideki Hosoda ,
Hiroshi Noma  and
Kenji Wakashima
Hideki Hosoda
Affiliation:
Precision and Intelligence Laboratory (P&I Lab), Tokyo Institute of Technology (Tokyo Tech), 4259 Nagatsuta, Midori-ku, Yokohama 226–8503, Japan, Phone&Fax 81–45–924–5057, email hosoda@pi.titech.ac.jp
Hiroshi Noma
Affiliation:
Precision and Intelligence Laboratory (P&I Lab), Tokyo Institute of Technology (Tokyo Tech), 4259 Nagatsuta, Midori-ku, Yokohama 226–8503, Japan, Phone&Fax 81–45–924–5057, email hosoda@pi.titech.ac.jp
Kenji Wakashima
Affiliation:
Precision and Intelligence Laboratory (P&I Lab), Tokyo Institute of Technology (Tokyo Tech), 4259 Nagatsuta, Midori-ku, Yokohama 226–8503, Japan, Phone&Fax 81–45–924–5057, email hosoda@pi.titech.ac.jp
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Abstract

B2 iridium aluminide (IrAl) is hopeful for use as an ultrahigh temperature oxidation resistant coating above 1600K. In this study, the effect of Co substitution for Ir on phase constitution, hardness and oxidation behavior was studied for IrAl alloys. Alloys of (Ir, Co)-50mol%Al with various Co contents were fabricated by Ar-arc melting followed by hot-forging at 1773K. Oxidation behavior was evaluated using thermogravimetry (TG) in Ar-67%O2 up to 1823K. XRD and SEM were also carried out for alloy characterization. It was found that a continuous B2 solid solution (Ir,Co)Al is formed between IrAl and CoAl. Depending on the Co concentration, the oxidation products identified after heating to 1873K in Ar-67%O2 were Ir, IrO2 and A2O3 and/or Co2AlO4. Thin and continuous Al2O3 layers were observed after isothermal oxidation at 1673K when Co content is more than 20mol%Co. In this case, the weight change by isothermal oxidation at 1673K becomes higher with decreasing Co content. The (Ir,Co)Al alloys containing 20–40mol%Co exhibit higher oxidation resistance than CoAl and IrAl, and thus oxidation resistance of CoAl is improved by Ir addition.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 753: Symposium BB – Defect Properties and Related Phenomena in Intermetallic Alloys , 2002 , BB5.32
Copyright
Copyright © Materials Research Society 2003

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References

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