Properties, processability and weldability of a novel affordable creep resistant nickel base superalloy

Abstract

A recently designed heat resistant alloy for operation ∼750°C in power plant, named FT750_DC, of composition Ni–20Cr–5Fe–3·5W–2·3Al–2·1Ti–0·07C–0·4Si–0·005B (wt-%), is fully characterised. Creep rupture and damage is investigated, as well as Charpy impact toughness. The alloy processability is also assessed: castability (comparison between measured microsegregation and Scheil simulation), forgeability (hot tensile ductility, strain hardening and recrystallisation behaviour), γ′ aging heat treatment (gamma-prime precipitation kinetics) and weldability (GTAW/TIG). It is demonstrated that this material, made affordable by avoiding the use of expensive alloying elements, with a creep rupture life in excess of 100 000 h at 750°C under 100 MPa, is easily castable, forgeable and weldable. It can therefore be favourably compared to concurrent alloys for fossil fuel or nuclear power plant applications (like the coal fired ultra supercritical steam power plant, or the nuclear high temperature gas cooled reactor) currently under assessment, such as alloys 230, 617, 625, 740, HX, etc.

Keywords:

• MECHANICAL PROPERTIES
• FRACTURE
• RESILIENCE
• WELD
• WELDING
• ATIG
• RECRYSTALLISATION
• SRX