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Microstructure and Oxidation Resistance of Cr-Ta-Si alloys

Published online by Cambridge University Press:  18 January 2011

Ayan Bhowmik ,
Hon Tong Pang ,
Steffen Neumeier ,
Howard J. Stone  and
Ian Edmonds
Ayan Bhowmik
Affiliation:
Rolls-Royce UTP, Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, United Kingdom
Hon Tong Pang
Affiliation:
Rolls-Royce UTP, Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, United Kingdom
Steffen Neumeier
Affiliation:
Rolls-Royce UTP, Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, United Kingdom
Howard J. Stone
Affiliation:
Rolls-Royce UTP, Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, United Kingdom
Ian Edmonds
Affiliation:
Rolls-Royce plc, P.O.Box 31, Derby, DE24 8BJ, United Kingdom
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Abstract

The phase equilibria and oxidation resistance of alloys lying near the Cr-rich end of the Cr- Ta-Si system have been investigated. Samples were prepared by arc-melting and homogenized at 1300°C for 500hrs. Identification of the phases present and their compositions were carried out using x-ray diffraction and electron probe micro-analysis and the ternary phase diagram on the Cr-rich end was plotted. A three-phase equilibria was found to exist between an A2 Cr-solid solution, a hexagonal Laves phase and the A15 Cr3Si intermetallic phase for alloys with higher contents of Si.Thermo-gravimetric analysis of the alloys at 1100°C demonstrated an improvement in the oxidation resistance of the ternary alloys with increasing Si-content. The microstructures of the oxidized samples revealed the formation of a thick chromia layer on top of a Cr,Ta-mixed oxide layer and an internal oxidation zone for all the alloys. A protective silica layer was not observed to form in any of the alloys tested.

Keywords

phase equilibriaoxidationthermogravimetric analysis (TGA)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1295: Symposium N – Intermetallic-Based Alloys for Structural and Functional Applications , 2011 , mrsf10-1295-n06-05
Copyright
Copyright © Materials Research Society 2011

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