HDP Coating

HDP Coating

The PVD deposition technology with cathodic arc has been considered a valuable method able to offer stable and constant results for a long time.

More and more effective coatings have been developed thanks to studies carried out over the years in order to further improve this technique. They have resulted in a performance which has overturned the methods used in machining processes.

However, research in this field has not stopped. It is still actively underway and surprising new products are being created. The most recent result of these efforts is HDP (High Density Plasma). This term refers to a highly developed high density plasma deposition system which makes it possible to achieve results never obtained before. The HDP system is based on the cathodic arc method.

It combines technical solutions that enable the deposition of coatings with process parameters which were considered impossible until now. Best results, such as the complete elimination of droplets, can be achieved (for many years droplets were considered inevitable within the arc technology). The deposition speed has also been increased significantly (4-5 microns per hour for AITiN type coatings).

If one examines the intrinsic structure of the coatings, very compact layers can be obtained using the HDP system thanks to the very high density of the plasma. It is also possible to maintain a very high degree of toughness. All this corresponds to an enormous potential in terms of mechanical resistance and makes it possible to increase the thickness of the coating, avoiding self-detachment phenomena due to internal stress.

One of the main objectives of research in this field is that of being able to deposit high thickness layers which were not being used before due to their great fragility. The achievement of this goal through the HDP system has made it possible to create an extraordinary barrier effect on the tool and, under certain application conditions, to increase its life and improve its performance significantly.

In order to appreciate the surprising advantages of the HDP technology it is absolutely necessary to optimize the cutting edge of the tool by eliminatine possible defects deriving from micro-splinters or from grinding residues, which could lead to premature breaking of the tooth (fig. 1 and fig. 2). The combination of an HDP coating with suitable preparation of the surface before coating, creates optimal conditions for carrying out difficult machining work (high cutting parameters) and to machine "hard to cut" alloys.

The HDP system is based on the high density of the plasma obtained using new cathodic sources combined with a pulsed polarization of the tools. Since deposition can take place both in a static and in a dynamic condition, layers can be combined in such a way as to create coatings which fulfil the requirements of specific machining processes in the best possible way.