Uwe Kopacz

Decorative hard coatings: new layer systems without allergy risk

Abstract Combinations of physically vapour deposited (PVD) coatings and electroplated layers are widely used for decorative applications. The electroplated layer beneath the PVD coating acts as a diffusion barrier. Conventionally electroplated barrier layers make use of nickel which has to be replaced in allergy-free systems by for example Ni/NiPd and CuSn(Zn). The PVD coating has to meet a variety of requirements: attractive colour, high wear resistance and good corrosion resistance. Within the scope of the search for new colours a number of nitrides of binary IVa metal-based alloys such as (Ti,V)N, (Zr,V)N, (Zr,Al)N, (Zr,Cr)N, (Zr,Y)N were deposited by reactive magnetron sputtering. To describe the colour the CIE L ∗ a ∗ b ∗ system was used. Spectroscopic ellipsometry (SE) was introduced to determine material related parameters. In general, both the stoichiometry and the structure can influence the colour of a coating. The correlation between colour, stoichiometry and structure was determined by surface analytical methods (glow discharge optical spectroscopy, Auger electron spectroscopy, X-ray diffraction). Proper selection of process parameters (target composition, N 2 flow rate, etc.) results in coatings with colours exceeding the conventional spectrum of decorative coatings. As an example of structural and stoichiometric influences on colour, ZrN and (Zr,Y)N coatings are discussed.

Morphology and properties of sputtered HfN layers as a function of substrate temperature and sputtering atmosphere

HfN layers were prepared by reactive rf‐magnetron sputtering onto polished flat high speed steel (HSS) surfaces. Rectangular samples were mounted on a special holder providing temperatures in the range of 775 to 300 K along the length of the sample. The HfN layers were deposited at various total pressures and different N2/Ar ratios. The film morphology and composition was studied by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES), respectively, and correlated with mechanical properties like microhardness and adhesion. The results are discussed with respect to the sputtering conditions.

Morphology and properties of sputtered TiN layers as a function of substrate temperature and sputtering pressure

Abstract TiN layers were prepared by r.f. magnetron sputtering onto polished flat high speed steel surfaces. The rectangular samples were mounted on a special holder, providing a temperature gradient in the range 775-300 K along the length of the sample. The TiN layers were deposited at various total pressures and different ratios of argon pressure to N2 pressure. The samples were fractured along a V-shaped notch. The film morphology was observed by scanning electron microscopy and correlated to mechanical properties such as microhardness and adhesion. The results are discussed with respect to the sputtering conditions.

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.

On the adhesion of nitride coatings on HSS substrates

Abstract The adhesion of reactively rf magnetron-sputtered nitride coatings (TiN, HfN, NbN) on HSS substrates was studied as a function of substrate temperature (775–300 K) and sputtering atmosphere (various total pressures and different N 2 /Ar ratios). The adhesion was tested by means of the scratch test and correlated to the film morphology. The critical load, as measured by the scratch test, is influenced by the properties of the substrate, the deposition conditions, the properties of the coating and the testing method. These dependencies are discussed in detail.