Development of new γ�-strengthened Co-based superalloys with low mass density, high solvus temperature and high temperature strength

Pandey, P and Mukhopadhyay, S and Srivastava, C and Makineni, SK and Chattopadhyay, K (2020) Development of new γ�-strengthened Co-based superalloys with low mass density, high solvus temperature and high temperature strength. In: Materials Science and Engineering A, 790 .

	PDF MAT_SCI_ENGA_790_2020.pdf - Published Version Restricted to Registered users only Download (4MB) | Request a copy
	Microsoft Word Mat_sci_eng_vol_790_2020 - Published Version Restricted to Registered users only Download (4MB) | Request a copy

Abstract

In this work we report new γ� strengthened cobalt base superalloys that have low mass densities in the range of ~ 8.3�8.5 gm/cm3, high solvus up to ~ 1128 °C and high specific 0.2 proof strength of ~ 90 MPa.gm-1.cm3 at temperatures up to 770 °C. The basic alloy composition is Co�10Al�5Cr�2Ta that exhibits γ/γ� microstructure on heat treatment. Electron diffraction and elemental partitioning across γ/γ� indicate the γ� has an ordered L12 structure with a stoichiometry Co3(Al,Ta,Cr) coherently embedded in disordered face-centered-cubic (fcc) γ-Co matrix. The γ� structure is primarily stabilized by Ta addition. The γ� volume fraction and the solvus temperature of the base alloy was measured to be 14 and 870 °C respectively. These values are significantly enhanced by the addition of 30at. Ni (35 and 975 °C) and together with 4at. Ti attaining the values of 63 and 1128 °C, respectively. Atom Probe measurements reveal both Ni and Ti strongly partition to γ� precipitates enhancing the stability of the γ' while Cr partitions to the γ phase. At 900 °C after 200 h of aging, the 30at. Ni added alloy without Ti reveals formation of coarsened γ� at the grain boundaries, directionally coarsened γ� with wavy γ/γ� interface and coagulated rod shape γ� inside the grains. Addition of Ti (2 and 4 at. ), however, suppresses the formation of these features up to 1000 h of aging at 900 °C. The feasibility of tuning the properties of the present alloys by alloying additions makes them attractive for their further development. © 2020 Elsevier B.V.

Item Type:	Journal Article
Publication:	Materials Science and Engineering A
Publisher:	Elsevier Ltd
Additional Information:	copy right for this article belongs to Elsevier Ltd
Keywords:	Grain boundaries; Nickel alloys; Superalloys, Alloy compositions; Alloying additions; Co-based superalloys; Cobalt-base superalloys; Elemental partitioning; Face-centered cubic; High temperature strength; Solvus temperature, Cobalt alloys
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	29 Nov 2024 10:14
Last Modified:	29 Nov 2024 10:14
URI:	http://eprints.iisc.ac.in/id/eprint/65707

Actions (login required)

View Item