Prediction of shape distortions of hard metal parts by numerical simulation of pressing and sintering

To calculate shape distortions of powder compacts during sintering, both die pressing and sintering processes were simulated for two hard metal parts by using the finite element method. The modified Drucker-Prager model with cap hardening and a micromechanical model based on the diffusion along grain boundaries were applied to simulate die pressing and sintering, respectively. The inhomogeneous density distributions caused by the pressing were computed and the shape changes of the parts during the subsequent sintering were predicted. A comparison between the numerical and experimental results for the first analyzed part shows that the undesired shape distortions of the powder compact can be very well calculated by the simulation method. The second example demonstrates that the numerical simulation can be used to optimize pressing schedule and punch forms.