Properties of nano-multilayered hard coatings deposited by a new hybrid coating process: Combined cathodic arc and unbalanced magnetron sputtering

Nano-scale multilayered coatings of (Ti,Al)N/SiN, (Ti,Al)N/WN, and CrN/BCN were deposited by a new hybrid coating process that combined cathodic arc and unbalanced magnetron sputtering (UBM). Cross-sectional transmission electron microscopy (TEM) analysis of the coatings deposited by the hybrid process revealed that these coatings had a multilayer structure in that layers deposited by the arc source and the sputter source were stacked alternatively. The bilayer period of the multilayer system was the function of the substrate rotation speed and the input power to the each evaporation source, and it was typically in the range of 10-20 nm. From X-ray diffraction measurements, in case of Si or B4C target used as a sputter target, the grain size was drastically decreased from 30 to 10 nm as the evaporation rate of the sputter source was increased. We confirmed from TEM observation that the grain growth of the (Ti,Al)N or CrN layer was interrupted at the interface and this resulted in much smaller grain size compared to the conventional (Ti,Al)N coating. Mechanical and tribological properties of different nano-multilayered coatings are discussed.