On the Effect of Nb on the Microstructure and Properties of Next Generation Polycrystalline Powder Metallurgy Ni-Based S
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On the Effect of Nb on the Microstructure and Properties of Next Generation Polycrystalline Powder Metallurgy Ni-Based Superalloys KATERINA A. CHRISTOFIDOU , MARK C. HARDY, HANG-YUE LI, CHRISTOS ARGYRAKIS, HIROTO KITAGUCHI, NICHOLAS G. JONES, PAUL M. MIGNANELLI, ALISON S. WILSON, OLIVIER M.D.M. MESSE´, ED J. PICKERING, ROBERT J. GILBERT, CATHIE M.F. RAE, SUYANG YU, ALEX EVANS, DANIEL CHILD, PAUL BOWEN, and HOWARD J. STONE The effect of Nb on the properties and microstructure of two novel powder metallurgy (P/M) Ni-based superalloys was evaluated, and the results critically compared with the Rolls-Royce alloy RR1000. The Nb-containing alloy was found to exhibit improved tensile and creep properties as well as superior oxidation resistance compared with both RR1000 and the Nb-free variant tested. The beneficial effect of Nb on the tensile and creep properties was due to the microstructures obtained following the post-solution heat treatments, which led to a higher c¢ volume fraction and a finer tertiary c¢ distribution. In addition, an increase in the anti-phase-boundary energy of the c¢ phase is also expected with the addition of Nb, further contributing to the strength of the material. However, these modifications in the c¢ distribution detrimentally affect the dwell fatigue crack-growth behavior of the material, although this behavior can be improved through modified heat treatments. The oxidation resistance of the Nb-containing alloy was also enhanced as Nb is believed to accelerate the formation of a defect-free Cr2O3 scale. Overall, both developmental alloys, with and without the addition of Nb, were found to exhibit superior properties than RR1000. https://doi.org/10.1007/s11661-018-4682-4 The Author(s) 2018
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INTRODUCTION
THE development of Ni-based superalloys has been inextricably linked to the needs of the aerospace industry and its regulators. Jet engines are continuously evolving to provide improved efficiencies combined with
KATERINA A. CHRISTOFIDOU, NICHOLAS G. JONES, PAUL M. MIGNANELLI, ALISON S. WILSON, CATHIE M.F. RAE, and HOWARD J. STONE are with the Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS, UK. Contact e-mail: [email protected] MARK C. HARDY, CHRISTOS ARGYRAKIS, ROBERT J. GILBERT, and DANIEL CHILD are with Rolls-Royce plc, Derby, DE24 8BJ, UK. HANG-YUE LI, HIROTO KITAGUCHI, SUYANG YU, and PAUL BOWEN are with the Metallurgy and Materials, The University of Birmingham, Pritchatts Road, Birmingham, B15 2TT, UK. OLIVIER M.D.M. MESSE´ is with the Department of Materials Science and Metallurgy, University of Cambridge and also with the Oerlikon Am GmbH, Feldkirchen, Germany. ED J. PICKERING is with the School of Materials, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK. ALEX EVANS is with Rolls-Royce Deutschland, BlankenfeldeMahlow, Germany. Manuscript submitted March 15, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
reduced environmental and acoustic emissions.[1,2] However, while aerodynamic design optimiz
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