The paper discusses the results of investigations of material, tribological and anti-corrosion properties of hybrid coatings of the Cr/CrN type, consisting of chromium and chromium nitride, formed on the surface of alloy tool steel by the Arc-PVD method. Investigations of the morphology and microstructure of hybrid coatings, as well as of their phase composition were carried out. The studies on mechanical properties included tests on hardness and Young’s modulus using the nanoindentation method. Tests on adhesion were conducted using the scratch-test method. Tribological properties of the obtained coatings were evaluated by the pin-on-disc method. Resistance to corrosion was determined by electrochemical methods. It was shown that hybrid coatings of the Cr/CrN type are characterized by good adhesion to the substrate and very good tribological properties, as well as by very good resistance to corrosion in a solution containing chlorine ions.
The objective of the research in this work was the modification of structure of carbide-type chromized layers, by the combination of diffusion chromizing with subsequent PVD treatment, consisting of chromium nitride deposition, carried out to improve their tribological properties. As a result, hybrid layers on the surface of tool steel were obtained. For comparison, the properties of single chromized carbide layers obtained in a diffusion chromizing process were tested. Investigations of layer microstructure, their mechanical properties, surface topography, adhesion of layers to the steel substrate, as well as tribological properties were conducted. The layer microstructure was characterized by X-ray diffraction and scanning electron microscopy. Topography of the layer surface was studied by an optical profilometer. The scratch test for investigations of layers adhesion to the steel substrate was used. Testing of tribological properties (linear wear) of the layers was performed by the three-cylinder-cone method. It was shown, that hybrid layers are characterized by a significantly smaller surface roughness than that of chromized carbide layers and their wear resistance improved almost twice with respect to carbide layers.
A short literature survey which justifies coating of ceramic cutting inserts is presented. The results reported are on selected nitride coatings, in particular nanoscale multilayer, with layers of type Ti-Zr-N, TiN, ZrN and (TiAl)N, deposited by the arc PVD method on oxidecarbide ceramic cutting inserts of type TACN and TW2 produced at the Institute of Advanced Manufacturing Technology. Measurements and quality assessments were made, including of thickness of the coatings and of their constituent micro and nanolayers, microhardness of the coating and of the substrate, surface roughness of the inserts and of the cylindrical workpieces turned with these tools. Lifetimes of the coated and uncoated inserts were compared in turning an alloy tool steel. A significant increase in lifetime of the coated TW2 cutting tools was shown.