Computer and physical modeling of multiple isothermal forging of EK61 superalloy

Abstract

Studies on the process of multiple isothermal forging of high-temperature nickel-based EK61 superalloy using computer simulation in the DEFORM-3D software package in a three-dimensional formulation and a comparison with experimental data were carried out. Based on the simulation results, it is shown that with each subsequent stage of forging, the maximum strain values become higher, and the strain differences in the central and peripheral regions become smaller. Such a strain distribution leads to the formation of a homogeneous ultrafine-grained (UFG) microstructure. The initial coarsegrained microstructure is gradually transformed into a fine-grained microduplex type microstructure at 0.77T melt and with a further decrease in the processing temperature to 0.73T melt , it is transformed into a submicroduplex type (γ + δ) UFG microstructure.

Superplastic forming of EK61 nickel-based superalloy with ultrafine-grained structure

“…The chemical composition of EK61 is 58Ni-16.6Cr-15Fe-3.9Mo-5Nb-Al-Ti-Cu-V [28 -30]. Russian wrought EK61 superalloy is a representative of heatresistant superalloys hardened by the γ''-phase [4,6,28]. The deformation-heat treatment was carried out to obtain an ultrafine-grained structure of a duplex type in the EK61 superalloy.…”

“…The multiple isothermal forging was carried out using an isothermal die block mounted on a hydraulic press with a force of 6.3 MN. Such processing was performed at the conditions established earlier in the temperature range of 950−750°C with a stepby-step decreasing of the temperature [9,11,16,28]. The total compression strain for forged billet was e ≈11.…”

“…In the initial state, the superalloy under investigation was a hot-deformed billet of 80 mm in diameter with an initial coarse-grained structure of γ-phase matrix with a grain size of 62 μm. In such coarse grains of matrix, the coherent nanosized (≈40 nm) particles of the strengthening γ''-phase were precipitated [28].…”