Effect of stabilisation on precipitation behaviour and mechanical properties of alloy GH4706

Abstract

Fe–Ni base superalloy GH4706 has been used for large size disc forgings of heavy duty gas turbines. In this paper, based on the change law of precipitation, influential effects of stabilisation time on precipitation behaviour and mechanical properties of GH4706 alloy were investigated. Results show that with prolongation of the stabilisation time, the morphologies of η phase changed from chain and rod-like to cellular, cluster and needle-shaped; meanwhile, large globular γ′ phase and rod-like γ″ phase gradually precipitated. Furthermore, the content of the η phase increased with increasing stabilisation time, and the precipitation free zone tended to be wider, owing to the reaction between the γ′ phase and the η phase. The room temperature and 650°C tensile strength and rupture life of the GH4706 alloy improved after stabilisation treatment at 845°C for 1–3 h.