SURFACE PREPARATION AND PVD COATING OF BROACHES

摘要

Over the recent years, newly developed protective coatings for cutting tools have become highly resistant to wear if exposed to the extreme environments associated with modern machining processes. Nowadays, the majority of currently used cutting tools, like hobs, broaches and drills made in HSS or carbide, have their cutting edges modified with a PVD coating. The use of PVD coatings allows to increase uptime, reduce maintenance, extend tool life and improve tools performances. Moreover, PVD technologies are more environmentally friendly than traditional coating processes. To take full advantage of the benefits offered by the PVD technique, a high quality coating must be produced from an adhesion e thickness point of view. Preparation and cleaning of the substrate prior to PVD coating is critical to the final performance of the coated product. Improper polishing, grinding, cleaning or preservation can lead to poor adhesion or premature failure of the coating. Only a metallic clean surface leads to good adhesion of the coating. Industrial cleaning units for fully automatic cleaning and vacuum drying have been developed to guarantee the perfect surface activation and cleaning of the parts to be coated, suitable also for difficult to clean parts with cavities. This paper describes the careful preparation of surfaces to be coated as well as the entire cycle of PVD coating of broaches. At the end, will be presented the control system developed to ensure the production of high and constant quality PVD coatings.