Metal-Ceramic composites and structures are of interest for a growing number of applications such as power electronics, electrical mobility and magnetic shielding due to the combination of thermal and electrical conductive and insulating zones. Locally changing the material properties throughout the component by carefull adjustment of the material composition allows to integrate irreconcilable properties in a single component. The mismatch in chemistry and properties however poses a significant challenge in producing such components. In this work we demonstrate the feasibility of making such materials using direct sintering of judiciously deposited commercial powders.
Graphite dies are filled using the Selective Powder Deposition (SPD) technology and subsequently consolidated using Field Assisted Sintering Technology (FAST). The SPD technology allows generating a 3D-structured powder bed that is, in essence, a precursor for the final product. Pre-compacting of the green powder deposit in the die locks the position of the individual powder particles in place, facilitating further processing. By employing materials with overlapping sintering windows, high density multi-material components can be achieved. Simultaneous application of current and pressure over the sample using the FAST sintering technique further extends these sintering windows. Delamination can be avoided by selecting materials with a small mismatch in coefficient of thermal expansion and maintaining the pressure during cooling. Residual thermal stresses can be engineered and predicted using modeling to determine the maximum allowable thickness of the individual layers, which can be controlled with high accuracy by the SPD technology.
If required, it is possible to generate functional gradients at the interface by inserting dithered/pixelated layers or zones within a single layer. In this manner a more gradual transition can be obtained from a full metal to full ceramic in all 3 dimensions.