J.J. Olaya

Unbalanced magnetic field configuration: plasma and film properties.

Coatings of CrN, TiN, ZrN, TaN and NbN were deposited using an unbalanced magnetron sputtering system with two different degrees of unbalancing to investigate the effect of the degree of unbalancing on both plasma characteristics and film properties. The degree of unbalancing was determined by an extensive characterization of the magnetic field fluxes in the X-Z plane perpendicular to the target. Then, the plasma parameters, such as electron temperature, plasma potential, plasma density and ion current density, were obtained for each target and as a function of the unbalance coefficient. The film microstructure, hardness, corrosion and wear resistant were measured to determine the effect of the degree of unbalancing on these properties. The results suggested that the degree of unbalancing, through the variations induced in the ion bombardment and plasma ionization, had a strong influence on the film hardness, microstructure and preferred orientation.

Corrosion behaviour of TaN thin PVD films on steels

Abstract The corrosion behaviour of tantalum nitride (TaN) thin films deposited on AISI 1018 carbon steel, AISI M2 tool steel and AISI 304 stainless steel has been investigated in an aqueous sodium chloride solution. The films were produced by means of magnetron sputtering plasma deposition. Morphological and microstructuctural characteristics of the films were studied by atomic force microscopy and X-ray diffraction analysis. Potentiodynamic polarisation, electrochemical impedance spectroscopy and cyclic voltammetry techniques were used for electrochemical characterisation. The TaN films displayed lower corrosion current densities than those of the substrates. A relaxation time in the impedance analysis was observed in the 1018/TaN system, two relaxation times were observed in the M2/TaN system, and a diffusion process was found in the 304/TaN system. This indicates that the substrates were not completely isolated from the solution and the defects in the films appear to be detrimental owing to electrolyte penetration through the defects which caused localised corrosion. The corrosion behaviour of the films depends mainly on the electrochemical properties of the substrate.

CORROSION RESISTANCE OF DECORATIVE CHROMIUM FILMS OBTAINED FROM TRIVALENT CHROMIUM SOLUTIONS

In this work, the resistance to corrosion of chromium films obtained from trivalent chromium solutions of different compositions and the influence of solution compounds on the coatings electrochemical behavior and the microstructure were studied. The chromium coatings were obtained from trivalent solutions in a chloride-based bath with different complexing agents adding also sodium hypophosphite and aluminum chloride. UV-vis spectroscopy was carried out on all solutions before and after plating to observe changes in the chromium complexes chemical state due to the plating process. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) were performed to examine the coatings surface morphology and composition; respectively. The coulometric method was used for measuring coating thickness. Electrochemical impedance spectroscopy (EIS) was done using 3% NaCl as electrolyte and using a three-electrode cell with a standard calomel electrode (SCE) as reference. Bright chromium films were obtained from all baths however, differences were observed concerning morphology, thickness and corrosion resistance depending on the composition of the forming solution.