Microstructure, mechanical and tribological properties of CrN/W2N multilayer films deposited by DC magnetron sputtering

CrN/W2N multilayer films with various bilayer periods of 15–85 nm were deposited on high speed steel (W18Cr4V) substrates by means of DC closed field unbalanced magnetron sputtering. The morphology and microstructure of the multilayer films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The mechanical and tribological properties were evaluated using a nanoindentor, Rockwell and scratch tests and a conventional ball-on-disk tribometer, respectively. There were some transverse grains at the layer interface and the interface between the CrN and W2N layers was not so sharp owing to atom diffusion through the interface. In the bilayer period range, the microhardness, elastic modulus and adhesive strength of the CrN/W2N multilayer films increased with the decrease of bilayer period. The CrN/W2N multilayer film with a bilayer period of 15 nm showed the highest hardness (29.2 GPa), elastic modulus (376 GPa) and best adhesion strength, it also had the highest wear resistance and lowest friction coefficient.