Investigations of nanocrystalline and gradient coatings produced by cathodic arc evaporation technology

Purpose: The main aim of the this research was the investigation of the microstructure, corrosion resistance and the mechanical properties of the nanocrystalline TiAlSiN, CrAlSiN, AlTiCrN and the gradient TiAlN, TiCN, AlSiCrN coatings deposited by cathodic arc evaporation technology onto the X40CrMoV5-1 hot work tool steel substrate. Design/methodology/approach: The surfaces’ topography and the microstructure of the investigated coatings were observed on the scanning electron microscopy. Diffraction and thin film structure were tested with the use of the transmission electron microscopy. The microhardness tests were made on the dynamic ultra-microhardness tester. Tests of the coatings’ adhesion to the substrate material were made using the scratch test. Findings: It was found that the microstructure of the nanocrystalline coatings consisted of fine crystallites, while their average size fitted within the range of 11-25 nm, depending on the coating type. The critical load LC2 lies within the range of 46-54 N. In case of the gradient coatings it was found that the microstructure consisted of crystallites while their average size fitted within the range of 25-50 nm, depending on the coating type. The coatings demonstrated columnar structure as well as good adhesion to the substrate. The critical load LC2 lies within the range 46-59 N. The coatings demonstrate a high hardness (40 GPa) and corrosion resistance. Practical implications: In order to evaluate with more detail the possibility of applying these surface layers in tools, further investigations should be concentrated on the determination of the thermal fatigue resistance of the coatings. The very good mechanical properties of the nanocrystalline and gradient coatings make them suitable in industrial applications. Originality/value: The investigation results will provide useful information to applying the nanocrystalline and gradient coatings for the improvement of mechanical properties of the hot work tool steels.