New Trends in Decorative Coatings 2 $ ? 6 ?
ecorative coatings applied with D . . sputter ion plating processes have become a widely accepted application for vacuum technology. Although the deposition itself is only one important step among others, indusmal decorative applications require a reproducible and productive coating system. Leybold, as a system manufacturer, is featuring machines with a high level of up-time as well as an extraordinary sales service. In addition, such equipment is able to control all manufacturing steps including the choice of substrate material, the proper machining of it, the advisable heat treatment, the correct surface machining, the appropriate electroplating and the right precleaning. All these factors have an important influence, since a successful product does not depend solely on film properties. All system features required in the performance portfolio need to be fulfilled. In some circumstances, features required for a satisfactory coating can only be determined in extensive field tests.
Decorative properties and chemical composition of hard coatings
Transition metal compounds (nitrides, carbides, etc.) find increasing use as decorative coatings combining intensive colours, high wear resistance and good corrosion resistance. While golden TiN and dark-grey TiC are limited in their colour variation, the addition of a second metal or a second metalloid widens the spectrum of decorative colours, e.g. to dark blue with (Ti, Al)N. In the search for new colours, a number of nitrides of binary IVa metal-based alloys were deposited by reactive magnetron sputtering. The correlation between colour and stoichiometry was determined by surface analytical methods. Proper selection of the process parameters (target composition, N2 flow rate, etc.) results in coatings with different colours exceeding the conventional spectrum of decorative coatings.
The reflectance and color of titanium nitride
It is shown that lattice expansion at constant composition can affect the location and slope of the reflectance curve of TiN films in a complex way comparable to the effect of substoichiometry or carbon substitution. Lattice expansion first shifts the reflectance shoulder to lower photon energies, causing the color (chroma) to lighten, and then to higher energies leading to a red cast. Tempering reduces the extremes but leaves a range of color where films made at lower deposition rates are more intensely yellow. The effects are discussed in terms of a simple ionic model and considering lattice defects.