Properties of Tool Steel After Hybrid Treatment Connecting Diffusion Chromizing with the PVD Method

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.