Effect of process modeling on product quality of superalloy forgings

Even so effects of forming, heating and cooling on microstructure and therefore mechanical properties are well understood for superalloys like alloy 718 the influence of complex multistep thermomechanical processes can not be described analytically. Thus the usage of simulation tools is a necessity in order to secure stable processes and resulting properties. With increasing computer power and the development of the finite element method it is today possible to simulate these processes with high accuracy in a sufficient time period. Typical simulation results like optimization of material input, a guaranteed die filling as well as prevention of folding or overheating will be part of the paper. In addition the benefits of recent developments on residual stress and distortion simulation as well as microstructure and nanostructure models and their influences on mechanical properties will be discussed. Finally some simulation examples including process variations and their effects on the quality of parts will be compared with results of microstructure evaluation and mechanical testing of forgings. Using these simulation approaches linked with recent developments on fatigue modeling, it is possible to obtain minimized weight and maximized lifetime in the final part and therefore optimize the total life cycle costs. (AU) © 2010 by The Materials, Metals, & Materials Society. All rights reserved.