SPUTTER DEPOSITION OF DECORATIVE COATINGS BASED ON ZRB2 AND ZRB12

Decorative coatings of zirconium boride and zirconium boron nitride were deposited onto steel and molybdenum substrates employing non-reactive and reactive d.c. magnetron sputter deposition using zirconium diboride (ZrB2) and zirconium dodecaboride (ZrB12) targets. The characterization of the coatings was by scanning electron microscopy and X-ray diffraction. The results are discussed in connection with measured mechanical and optical film properties such as microhardness and CIE-L*a*b* values. By means of nonreactive sputtering, fine-columned films with a predominantly (001)-orientated ZrB2 phase were formed; in the case of sputtering from the ZrB12 target the ZrB2 phase was accompanied by the rhombohedric B phase. Reactive deposition at low nitrogen flow rates leads to the formation of a hexagonal Zr-B-N phase based on ZrB2 (using the ZrB2 target), accompanied by a highly distorted B phase (using the ZrB12 target). The further incorporation of nitrogen leads to amorphous film growth. The maximum Vickers microhardness of the coatings was found to be approximately 2300 HV0.01. These coatings offer an excellent choice for decorative applications with colours from silver-grey to black combined with outstanding corrosion and abrasion resistance.