Microstructure Modeling of the Dynamic Recrystallization Kinetics during Turbine Disc Forging of the Nickel Based Superalloy Allvac 718 Plus

Abstract

The outstanding mechanical properties of the nickel based superalloy Allvac 718Plus T M are sensitive to the microstructure, in particular to the grain size, which depends on the processing history. The grain structure is mainly controlled by thermo-mechanical processes like recrystallization and grain growth. This paper deals with the simulation of the evolution of the grain structure in alloy Allvac 718Plus T M during disc forging using the Finite Element (FE) code Deform 2D T M . Additionally the material flow, pressing forces and temperatures are of interest. The hot deformation behaviour of Allvac 718Plus T M has been characterized in a temperature range of 900-1050 C and at strain rates of 0.1-10 s -1 by use of cylindrical compression tests. Particular emphasis is put on the identification of the parameters of a semi-empirical model for dynamic recrystallization. Furthermore the simulated results are compared with an industrial trialforging. The results of the simulations shall be the basis for the development of an optimized forging process with respect to cost effectiveness, product quality and low energy consumption.