Influence of microstructure and processing on mechanical properties of advanced Nb-silicide alloys
- PDF / 354,904 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 50 Downloads / 232 Views
Influence of microstructure and processing on mechanical properties of advanced Nb-silicide alloys C. Seemüller1*, M. Heilmaier1, T. Hartwig2, M. Mulser2, N. Adkins3, and M. Wickins3 1 Physical Metallurgy, IAM-WK, Karlsruhe Institute of Technology, Engelbert-Arnold-Str. 4, 76131 Karlsruhe, Germany 2 Powder Technology, Fraunhofer Institute for Manufacturing Technology and Advanced Materials, Wiener Straße 12, 28359 Bremen, Germany 3 IRC in Materials Processing, The University of Birmingham, Elms Road, Edgbaston, Birmingham B15 2TT, UK.
*Corresponding author: Tel. +49 721 608 46556, [email protected]
ABSTRACT In this study different powder metallurgical processing routes, commonly used for refractory metal based materials, were evaluated on their impact on mechanical properties of a multicomponent Nb-20Si-23Ti-6Al-3Cr-4Hf (at.%) alloy. Powder was produced by gas-atomization or high energy mechanical alloying of elemental powders and then consolidated either by HIPing or powder injection molding (PIM). The PIM process requires fine particles. In this investigation powder batches of gas-atomized powder (< 25 μm) and mechanically alloyed powder (< 25 μm) were compacted via PIM. Fine (< 25 μm) and coarser (106-225 μm) particle fractions of gasatomized powder were compacted via HIPing for comparison. Quantitative analysis of the resulting microstructures regarding porosity, phase formation, phase distribution, and grain size was carried out in order to correlate them with the ensuing mechanical properties such as compressive strength at various temperatures. INTRODUCTION In the hot sections of today’s turbines mostly nickel-base superalloys are used which operate at homologous temperature up to about 0.85 (1100 °C). To improve turbine efficiency the temperature has to be further increased requiring new materials with increased melting temperature. Niobium based silicide (NbSi) composites are a promising materials group to reach that goal. Powder metallurgical processing routes give the opportunity to obtain a fine-grained, homogeneous microstructure. Compaction processes like powder injection molding (PIM), netshape hot isostatic pressing (HIP), or selective laser melting (SLM) provide the ability to produce near net shape components, requiring a minimum effort in post processing. They also yield potential in cost reduction compared to classical casting techniques. At present, however, NbSi-alloys still remain in the development stage leading to alloys mostly being produced by arc-melting/casting [1-3]. By contrast, powder metallurgical approaches with NbSi-alloys have been scarcely investigated in literature [4], despite being a promising method. Therefore, the goal in the present study is to compare the impact of two different powder production routes, namely mechanical alloying (MA) and gas-atomization (GA), combined with different compaction methods such as hot isostatic pressing and powder injection molding on microstructure and mechanical properties of Nb-Si alloys.
317
EXPERIMENTAL DETAILS Powder pro
Data Loading...
