Tribological behaviour of DLC-films and their application in micro deep drawing

In this work, the tribological behaviour of DLC-coated as well as uncoated tools was characterized by tests on a tribometer. Special attention was paid to assess how the failure mechanisms of the films proceed, for example, whether the so-called “eggshell effect” plays a role in the failure of the films. Compared to the uncoated tools, the DLC-coated tools showed a significantly lower friction coefficient to the work piece material stainless steel X5CrNi18-10. As the contact pressure was varied from 215 to 330 N/mm2, which is comparable to the maximum contact pressure in deep drawing, no damages in form of cracks or flaking were observed. Furthermore, lubricant-free micro deep drawing was performed with DLC-coated tools made of tool steel X153CrMoV12. Though no lubricant was used, the experimentally measured punch force was lower than that from experiments using lubricant with uncoated tools. This indicates that the DLC-coating has a great application potential in micro forming.

► Within the investigation using a tribometer, the DLC-film shows a very good resistance against stainless steel. ► The DLC-coated forming tools are successfully applied in lubricant-free micro deep drawing. ► The measured punch force is smaller than that in lubricated micro deep drawing with uncoated forming tools. ► No eggshell effect was observed on the surface of the DLC-coated forming tools.