Achieving lower mass density with high strength in Nb stabilised γ/γ′ Co–Al–Mo–Nb base superalloy by the replacement of Mo with V

Singh, MP and Makineni, SK and Chattopadhyay, K (2020) Achieving lower mass density with high strength in Nb stabilised γ/γ′ Co–Al–Mo–Nb base superalloy by the replacement of Mo with V. In: Materials Science and Engineering A, 794 .

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Abstract

We report new compositions of γ/γ′ Co base super alloys with low mass density where the strengthening γ′ precipitates Co3(Al0.45V0.33Nb0.21) are stabilised with a systematic replacement of Mo with V in Co–10Al–5Mo–2Nb (all in at.%) superalloy. The γ/γʹ microstructure is found to be metastable in nature that decomposes into equilibrium phases after 200 h of aging at 800 °C. Diffraction and atomic-scale compositional analysis reveal that phases are a γ-Co solid solution with composition Co-6.9Al–5V-1.4Nb, a B2 ordered Co(Al,V) phase with composition Co-34.6Al-5.6V and a DO19 ordered Co3Nb phase with composition Co-23.4Nb-1.6Al. Addition of 30 at.% Ni to the Co–10Al–5V–2Nb superalloy increases the γ′-solvus temperature to 1017 °C with improved high temperature strength and stability, concomitantly achieving a yield strength of 701 ± 9 MPa at 770 °C. The γ/γʹ microstructure of the alloy is found to be stable at 800 °C and 900 °C till 1000 h. Vanadium addition, therefore, have marked beneficial effect in cobalt base superalloys indicating good potential for future alloy development.

Item Type:	Journal Article
Publication:	Materials Science and Engineering A
Publisher:	Elsevier Ltd
Additional Information:	The copyright for this article belongs to Elsevier Ltd.
Keywords:	Aluminum alloys; Metastable phases; Microstructure; Molybdenum; Niobium; Niobium alloys; Superalloys, Alloy development; Beneficial effects; Cobalt-base superalloys; Compositional analysis; Equilibrium phasis; High temperature strength; Solvus temperature; Vanadium addition, Cobalt alloys
Department/Centre:	Division of Interdisciplinary Sciences > Interdisciplinary Centre for Energy Research Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	14 Feb 2023 08:41
Last Modified:	14 Feb 2023 08:41
URI:	https://eprints.iisc.ac.in/id/eprint/80233

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