SPUTTER-DEPOSITION OF DECORATIVE BORIDE COATINGS

Decorative hard coatings have to meet a variety of requirements such a s attractive colour as well as high wear and corrosion resistance. Aft er a review of PVD coatings used for decorative metal-finishing, an ac count is given of studies to extend the range of useful coating materi als. Within the scope of the search for new colours several borides su ch as zirconium diboride ZrB2, lanthanum hexaboride LaB6 and zirconium dodecaboride ZrB12 were evaluated using magnetron sputtering. The nit rogen flow in a partially reactive process was used as an additional d eposition parameter to influence film composition and properties. The interrelationships between structure, chemical composition and mechani cal as well as optical properties were investigated. By means of non-r eactive sputtering, crystalline films containing the ZrB2 or the LaB6 phase were formed. In the case of sputtering from the ZrB12, target, t he ZrB2 phase was accompanied by a highly disordered boron or boron-ri ch phase. The incorporation of nitrogen leads to increasing lattice di stortion and amorphous film growth at high concentrations. Among the c oating types with interesting properties are nitrogen containing films sputtered reactively from ZrB2 target's that had an anthracite colour ed surface and outstanding corrosion resistance. Violet coloured coati ngs deposited non-reactively from LaB6 targets are also potential cand idates for decorative applications.