Influence of the incremental deformation during rotary forging on the microstructure behaviour of a nickel-based superalloy

The incremental nature deformation of the rotary forging has great influence on the microstructure evolution during hot working achieving an instant recrystallisation from the beginning and reducing the forming force and obtaining higher deformation proportions compared with conventional forging operation. Mechanical properties of the nickel-based superalloy are sensitive to the grain size, which, in turn, is altered by the forging temperature, strain rate, strain and metallurgical phenomena. In order to get a better understanding of the influence of the incremental deformation on the microstructure evolution, a numerical model to forge a nickel-based superalloy disc has been developed into finite element platform, DEFORM™ 3D. The deformation characteristic of the workpiece was defined and processing parameters such as friction coefficient, workpiece preheating, tool temperature and cooling impact were studied, to relate the microstructural behaviour. The study of the grain size control has been carried out considering fine and coarse initial grain size coupling a phenomenological model into a finite element code. A fully recrystallised microstructure was obtained with a standard deviation of 0.5 μm; the simulated grain size was compared with experimental results.