Diamond-Like-Carbon Coated Dies for Electromagnetic Embossing (2020)

Herrmann, M.; Beckschwarte, B.; Hasselbruch, H.; Heidhoff, J.; Schenck, C.; Riemer, O.; Mehner, A.; Kuhfuss, B.

Materials 2020,13, 4939; doi:10.3390/ma13214939


Electromagnetic forming is a high-speed process, which features contactless force transmission.Hence, punching operations can be realized with a one-sided die and without a mechanical punch.As the forces act as body forces in the part near the surface, the process is especially convenient forembossing microstructures on thin sheet metals. Nevertheless, the die design is critical concerningwear like adhesion. Several die materials were tested, like aluminum, copper as well as differentsteel types. For all die materials adhesion phenomena were observed. To prevent such adhesion ana-C:H-PVD (Physical Vapor Deposition)-coating was applied to steel dies (X153CrMoV12) and testedby embossing aluminum sheets (Al99.5). By this enhancement of the die adhesion was prevented.Furthermore, the die surface was structured with tribology-effective patterns that were generated bymicro hard milling. The embossing quality was topographically analyzed with respect to differentinitial surface states of the sheets. It was identified that thicker sheets facilitate better embossing results.Moreover, the initial sheet surface has a decisive influence on the embossing quality, whereby thecharacteristic of the topography showed different susceptibility on the initial sheet surface state.

Keywords: impulse forming; adhesion; micro hard milling; hardened tool steel; a-C:H coating