Microstructural simulation of nickel base alloy Incone* 718 in production of turbine discs

Abstract

Modelling and simulation of microstructural development is of increasing interest especially for the production of critical components for aeronautical applications such as turbine discs. In this paper a model is presented which can predict microstructural changes of nickel base Inconel 718 during hot forming by means of semi-empirical equations. To determine the necessary parameters for reliable prediction, hot compression tests were carried out in a temperature range of 950 to 1150°C for strain rates of 0·005 to 10 s⁻¹. The measured data and the derived characteristic equations for the description of the hot deformation behaviour were incorporated into a finite element program and two industrial forging strategies for the production of turbine discs were simulated. The finite element program used was extended by a module to take the velocity characteristics of a counterblow hammer into account. Thus, a prediction of grain size evolution and recrystallised volume fraction during industrial hot working was facilitated which can be utilised for the planning of forging operations with respect to achieving the desired material properties.

MST/3362