Hollow cathode effect in a glow discharge for cleaning and heating substrate surfaces during wear-resistant coating deposition

This work explores applying the hollow cathode effect in a glow discharge for preliminary surface preparation and heating before wear-resistant coating deposition on metal-cutting tools. This study compares the properties of coatings deposited using the hollow cathode effect spaces (HCS) method and ion bombardment (IB) with plasma generation by arc evaporators. Applying HCS heating offers a smaller spread of the sample temperature throughout the chamber volume compared to that of IB heating. The proposed HCS method enables ion cleaning and heating workpieces to the temperatures required in PVD processes. The heating rate is significantly dependent on the pressure in the vacuum chamber and the voltage applied to the substrate. The IB coating begins to deteriorate at a load of 36 N during the scratch test due to fragmentary detachment from the substrate. Upon reaching the maximum load of 40 N, no signs of destruction of the HCS coating were observed. The results of the cutting test when turning steel reveal that, at a cutting speed of vc = 300 m/min, a tool with the HCS coating displays less active wear dynamics than a tool with the IB coating. The cutting test results for carbide inserts with and without the studied coatings reveal that the insert with the HCS coating has a slightly higher tool life (24 min) than the insert with the IB coating (18 min). When employing the IB method, a layer with a high cobalt content and the presence of other (polluting) elements may form at the coating-substrate interface, which can adversely affect the overall adhesion strength of the coating and substrate. When applying the HCS method, the formation of such a layer was not detected. Thus, HCS can be considered an effective alternative to IB.