Sputtered decorative hard coatings within the system LaB6-ZrB2

Decorative coatings have to meet a variety of requirements such as attractive colour as well as high wear and corrosion resistance. Within this work, coatings were deposited onto steel and molybdenum substrates by non-reactive magnetron sputtering using various targets within the quasi-binary eutectic section LaB6-ZrB2 with the goal to improve the mechanical properties of violet coloured LaB6-based coatings. Coating characterization was done using scanning electron microscopy, electron-probe microanalysis, X-ray diffraction, Vickers microhardness measurements and CIE-L*a*b* colorimetry. For sputtering from both compounds of the section LaB6-ZrB2, violet and silver-grey crystalline films with high hardness values were respectively obtained. For the ZrB2 target contents investigated within the two-phase region of the equilibrium diagram (25, 55, and 75 at.% ZrB2), coatings showed a pronounced tendency to form partially or fully amorphous structures. These structures were accompanied by low hardness values and a silver-grey appearance. Although being unsuccessful with optimization of both mechanical and optical properties of ZrB2-alloyed LaB6-based coatings, complex hard coatings have a substantial development potential in various application fields.