Contact resistances in spark plasma sintering: From in-situ and ex-situ determinations to an extended model for the scale up of the process

Heating in spark plasma sintering is a key point of this manufacturing process that requires advanced simulation to predict the thermal gradients present during the process and adjust them. Electric and thermal contact resistances have a prominent role in these gradients. Their determination is difficult as they vary with pressure and temperature. A calibration method is used to determine all of the contact resistances present within tools of different sizes. Ex situ measurements were also performed to validate the results of the in-situ calibrations. An extended predictive and scalable contacts model was developed and reveals the great importance and diversity of the contact resistances responsible for the general heating of the column and high thermal gradients between the parts. The ex/in situ comparison highlights a high lateral thermal contact resistance and the presence of a possible phenomenon of electric current facilitation across the lateral interface for the high temperatures.