Characteristic features of fine-grained coatings deposited on magnesium alloys

Purpose: This work presents the research results on the structure of gradient/monolithic coatings (Ti/Ti(C,N)/CrN, Cr/CrN/TiN) deposited onto the magnesium alloy substrate by cathodic arc evaporation method. Design/methodology/approach: The investigations were performed using scanning and transmission electron microscopy (with different image techniques) for the microstructure determination. The morphology was studied as well as the lattice parameters for the layer matrix and substrate phase identification using diffraction methods. Findings: A thin metallic layer (Ti and Cr) was deposited prior to deposition of gradient coatings to improve adhesion. It was found out that the microstructure of the PVD coatings deposited by the cathodic arc evaporation method is composed of fine crystallites and that their average size is in the range of 15-200 nm, depending on the coating type. SEM micrographs showed that the deposited coatings are characterized by compact structure without delamination or defects and they closely adhere to each other. Investigations confirm also that the Ti(C,N)/CrN and CrN/TiN coatings reveal a clearly visible transition zone between the gradient Ti(C,N) and CrN layers and the wear resistant CrN and TiN layers, obtained as a result of the separately applied metal vapour sources. Practical implications: Achieved coatings with good adhesion and without the disadvantage of delamination was made possible by cathodic arc evaporation method. Obtained properties of gradient/monolithic coatings (Ti/Ti(C,N)/CrN, Cr/CrN/TiN) deposited onto the magnesium alloy substrate and the study of them can contribute to development in a given group of materials used for different surface engineering processes. Originality/value: The original value of the work is that it applied the PVD method for a common material like magnesium alloy.