Incremental dry forging - Interaction of W-DLC Coatings and Surface Structures for Rotary Swaging Tools

Rotary swaging is an incremental cold forging process with very short cycle times for manufacturing of complex bar or tube profiles such as axles or gear shafts made of steel or aluminum alloys. Conventional rotary swaging requires high amounts of lubricants usually made of crude oil. Dry rotary swaging would improve the ecological balance of this process considerably and would also accelerate the process due to cleaning of the manufactured components after processing becomes obsolete.This study deals with a first benchmark of dry rotary swaging as a function of macro and micro-structured tool surfaces coated with wear resistant and low friction a-C:H:W coating systems with respect to the resulting workpiece quality and tribological process conditions. In addition, the influence of a surface finishing is investigated related to the dominating and locally changing coating wear mechanisms. The presented results allow for further coating development towards dry rotary swaging.