TY - JOUR
T1 - Effect of Cr addition on the phase equilibria and oxidation behavior of NbSi2
AU - Sekido, Nobuaki
AU - Aizawa, Ryoma
AU - Ueno, Shunkichi
N1 - Funding Information:
A part of this study is financially supported by KEIRIN, which is gratefully acknowledged.
Publisher Copyright:
© 2019 The Japan Institute of Metals and Materials.
PY - 2019
Y1 - 2019
N2 - Effect of Cr addition on the phase equilibria and oxidation behavior of NbSi2 was investigated. Although the crystal structures of NbSi2 and CrSi2 are both C40, they form separated ranges of homogeneities in the NbCrSi ternary system. The vertical section passing through the NbSi2 and CrSi2 binary edges were experimentally determined. A binary NbSi2 alloy exhibited poor oxidation resistance, showing pest-like behavior upon cyclic oxidation at temperatures from 800 to 1200°C. On the other hand, Cr addition significantly improved the oxidation resistance of NbSi2. The oxide layers that developed on the NbCrSi ternary alloys consisted of NbCrO4, Cr2O3, and SiO2, and the formation of Cr2O3 and NbCrO4 suppresses the Nb2O5 formation, and thereby suppresses the pest-like behavior of the binary NbSi2 alloy. However large Cr additions that exceed the solubility limit of NbSi2 should not be suitable, because NbSi2/CrSi2 alloys were susceptible to spalling and disintegration of the oxide scales upon cyclic oxidation. [doi:10.2320/matertrans.MB201809]
AB - Effect of Cr addition on the phase equilibria and oxidation behavior of NbSi2 was investigated. Although the crystal structures of NbSi2 and CrSi2 are both C40, they form separated ranges of homogeneities in the NbCrSi ternary system. The vertical section passing through the NbSi2 and CrSi2 binary edges were experimentally determined. A binary NbSi2 alloy exhibited poor oxidation resistance, showing pest-like behavior upon cyclic oxidation at temperatures from 800 to 1200°C. On the other hand, Cr addition significantly improved the oxidation resistance of NbSi2. The oxide layers that developed on the NbCrSi ternary alloys consisted of NbCrO4, Cr2O3, and SiO2, and the formation of Cr2O3 and NbCrO4 suppresses the Nb2O5 formation, and thereby suppresses the pest-like behavior of the binary NbSi2 alloy. However large Cr additions that exceed the solubility limit of NbSi2 should not be suitable, because NbSi2/CrSi2 alloys were susceptible to spalling and disintegration of the oxide scales upon cyclic oxidation. [doi:10.2320/matertrans.MB201809]
KW - Nb disilicides
KW - NbCrO
KW - Oxidation
KW - Phase diagram evaluation
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U2 - 10.2320/matertrans.MB201809
DO - 10.2320/matertrans.MB201809
M3 - Article
AN - SCOPUS:85065430727
VL - 60
SP - 666
EP - 673
JO - Materials Transactions
JF - Materials Transactions
SN - 1345-9678
IS - 5
ER -