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Article Title

Deformation in Superplasticity Regime – an Effective Method of Producing Components from Hetero- Phase Nickel-Based Alloys with Functional-Gradient Properties

Authors

V. Valitov 1
1 - Institute of Problems of Metals Superplasticity Russian Academy of Sciences

Volume

1 (2018)

Keywords

Superplastcity; strength properties; temperature-velocity regime; microduplex structure; necklace structure; fine-grained structure; deformation; thermal mechanical treatment

Abstract

The example of a deformable nickel alloy of the Ni–13Cr–10.7Co–4.6Mo–3.4Nb–3.2Al–2.6Ti–2.8W type and Astroloy alloy confirms that a regulated change in the deformation regimes and heat treatment in semi-finished products and parts can create regulated structural states that ensure the achievement of the required characteristics of technological and operational properties. The paper demonstrates the possibility of using a local fabrication scheme in the superplasticity (SP) temperature-velocity regime to produce gas turbine engine (GTE) components with a regulated change in the microstructure along the cross section (a fine grain microduplex structure in the hub, a mixed “necklace” type in the web and a coarse grain structure with tortuous grain boundaries in the disc rim). The results of mechanical tests of the samples showed that such a controlled change in the microstructure along the cross section resulted in the enhanced properties of various parts of the component in the interval of operating temperatures. A fine-grained microduplex structure, formed in the zone of the part operating at low temperatures, results in the highest strength properties. A coarse-grained structure with tortuous grain boundaries, which was obtained in the most heated zone of the component – the web, resulted in the maximum heat-resistant properties. In the zone of the web working at moderate temperatures, a mixed “necklace” type structure was formed, which resulted in enhanced strength and heat resistance properties due to the effect of sub-structural hardening. Similar results were obtained by deforming the Astroloy powder alloy. The comparative analysis of the obtained results with the known enables to conclude that deformation in the SP temperature-velocity regime combined with heat treatment in the (γ+γ′)-region is a kind of thermomechanical treatment resulting in short-term and high-temperature properties necessary for essential components made from hetero-phase nickel alloys used in the designs of aircraft and ground power plants.

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