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August 23, 2012

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daisymae

"We support public administration and local governments in driving profitable projects and working with our private partners."
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Ruth M Dasary

Nb- Re alloys have been studied in the pasy and the advantages might help the naval research to acheieve a alloy system where it can with stand, the high temperature applications.

Re forms a silicide layer (different forms at different temepratures) which is assumed as a protective layer. Upon addition of different elements like Cr, Mo,W would definitely help in reduction of pesting at lower temepartures.

My Abstract:

Effect of Re on the oxidation resistance of Nb base alloys has been studied in air over a range of temperature from 700 to 1400oC. The oxidation results of Nb-5Re, Nb-5Si, and Nb-5Cr binary alloys exposed for 24 hours in air in this temperature range will be compared with ternary alloys Nb-5Re-5Cr and Nb-5Re-5Si. Nb-5Re-5Cr-5Si quaternary alloy has been treated under identical oxidation conditions. Initial results on binary Nb-5Re alloy forms Re3O10 and the formation of base centered monoclinic form of b-Nb2O5 in Nb-5Si alloy at 900 and 1000oC. Ternary alloy Nb-5Re-5Si shows b-Nb2O5 at 900oC and ReO3 at 700 and 800oC.

Brenda R Arellano

This article illustrates that the effort to develop better high temperature materials is a challenge due to the aggressive environments of high temperature applications. By operating at a higher temperature, gas power plants will save energy. Nickel based alloys have always been the choice for turbine blades but they are coming close to their operating limit. If the operating temperature increases, a liquid phase may form. Metallurgists at the University of Texas at El Paso have been conducting research on studying the oxidation behavior of Niobium based alloys for the replacement of Nickel based superalloys. The oxidation resistance of Niobium alloys is a serious problem and many researchers have studied Nb-based alloys with additional alloying elements such as Si, Al, Ti, Cr, Hf, B, and Mo. The addition of Al to Nb-alloys has increased the oxidation resistance due to the presence of the Al2O3 phase which has proven to increase the oxidation resistance. More additions of Al may provide a larger protective oxide layer.

References:
B. P. Bewlay, M. R. Jackson, J.-C Zhao, P. R. Subramanian, Metall. Mater. Trans. 34A (2003) 2043-2052
T. Murakami, S. Sasaki, K. Ichikawa, A. Kitahara, Intermetallics 9 (2001) 629-635
D.Alvarez, S.K. Varma, Corrosion Science, Vol 53, Issue 6 (2011) 2161-2167

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