Investigation of the interactions of an incremental edge zone reshaping and a HPPMS coating on fineblanking punches to enable a load appropriate adjustment of surface integrity (TEStOI)

 

When processing high-strength sheet metal materials for the production of functional components, such as brake lining carriers in the automotive industry, by means of fine blanking, the tool stress increases compared to conventional sheet metal materials. Incremental processes for mechanical surface treatment, such as deep rolling, are suitable for increasing tool life by increasing wear resistance. The reason for this is an improvement in surface integrity (OI) due to mechanical surface treatment. The OI includes microstructure, hardness curve, residual stress condition, surface topography and damage to the tool edge zone.

To further reduce abrasive and adhesive wear, the functional surfaces of tools are coated by physical vapor deposition (PVD). Through knowledge-based process control during coating, it is possible to specifically influence the OI of the coating. This also has a positive effect on the OI of the tool edge zone and the bond strength. In particular, however, the residual stresses and the microstructure of the tool edge zone are successively relaxed by thermal stress during the coating process and by cyclic elasto-mechanical stress on the edge zone during precision cutting. The corresponding physical cause-effect relationships in the thermal and elastic stability of the OI are largely unknown.

On the one hand, it is unclear how the heat input in the coating process changes the OI of the tool and which interactions occur between the OI of the coating and the incrementally adjusted OI in the tool. On the other hand, it is unknown how the cyclic, elastomechanical continuous load during fine cutting affects the OI of the tool edge zone. Overall, the project is therefore based on the research hypothesis that the OI of the tool, which is specifically adjusted by an incremental edge zone forming and by the coating, can be designed in such a way that it is stable in a coating process at substrate temperatures T < 300 °C and under a subsequent friction-induced thermal and cyclic mechanical load. The thermal and elastic stability of the OI of the tool edge zone and the influence of the OI of the PVD coating will be investigated. The powder metallurgically produced high-speed steel S390 is used. On the one hand, the OI of tool edge zones is specifically adjusted and then the tool surface is coated in high-performance plasma processes. On the other hand, the tool edge zone and coating are investigated in order to analyze the influences of the machining processes and to derive a suitable process combination. The behaviour of the OI is investigated in a numerical simulation in order to expand the findings.