[Show abstract][Hide abstract] ABSTRACT: This paper reports on the preparation of TiNx thin films by d.c. reactive magnetron sputtering. The coating thickness ranged from 1.7 to 4.2 μm and the nitrogen content varied between 0 and 55 at.%. X-Ray diffraction showed the development of the hexagonal α-Ti phase, with strong  orientation for low nitrogen contents, where the N atoms fit into octahedral sites in the Ti lattice as the amount of nitrogen is increased. For nitrogen contents of 20 and 30 at.%, the ε-Ti2N phase appears with  orientation. With further increasing the nitrogen content, the δ-TiN phase becomes dominant. The electrical resistivity of the different compositions reproduces this phase behavior. The hardness of the samples varied from approximately 8 GPa for pure titanium up to 27 GPa for a nitrogen content of 30 at.%, followed by a slight decrease at the highest contents. A similar increase of stresses with nitrogen is observed. Structure and composition with the consequent changes in crystalline phases and the lattice distortion were found to be crucial in the evolution of the mechanical properties.
Full-text · Article · Feb 2005 · Surface and Coatings Technology
[Show abstract][Hide abstract] ABSTRACT: Within the frame of this work, coloured films based on single layered titanium oxynitride (TiNxOy) compounds were prepared. The films were deposited by r.f. magnetron sputtering under variation of process parameters such as bias voltage and flow rate of reactive gases. Colour varied from shiny golden type for low oxygen contents (characteristic of TiN films) to dark blue for higher oxygen contents. The information on the composition was obtained by Rutherford backscattering spectrometry. X-ray diffraction results revealed the development of a face-centred cubic phase with 〈111〉 orientation (TiN type; lattice parameter of ∼0.429 nm) and traces of dispersed oxide phases. Nanoindentation experiments showed values of hardness between 20 and 40 GPa, strongly dependent on the composition and microstructure. Compressive stresses between −0.5 and −6 GPa were determined by the deflection method.
[Show abstract][Hide abstract] ABSTRACT: TiN hard coatings with thickness ranging from 1.2 to 3.5 μm were prepared by r.f. reactive magnetron-sputtering in an Ar/N2 gas mixture. Texture, residual stresses, hardness and adhesion as a function of the r.f. power and bias voltage were investigated. X-ray diffraction experiments showed a unique δ-TiN phase for all the samples. All coatings revealed residual compressive stresses, whose amplitude increased with the r.f. power up to 800 W, followed by a slight decrease. The increase in adatom mobility is the main parameter that explains this behaviour up to 800 W, whereas the decrease observed for r.f. powers above 800 W can be explained from the stress relaxation that occurs due to internal cracks resulting from the large amount of accumulated elastic stresses. Defect annihilation effect is the main parameter, which can explain the stress behaviour at higher bias voltages. The effect of ion bombardment and the defect creation at the lower negative voltages are the main parameters that explain the increase observed in stress state. Residual stresses together with the reduced grain size are the main factors that seem to control the hardness and adhesion behaviour. Differences in failure mechanisms were detected with the variation in the deposition conditions, indicating a clear influence in coating performance.
[Show abstract][Hide abstract] ABSTRACT: SixCyNz thin films were deposited by reactive magnetron sputtering on glass and steel substrates. The films were grown in a rotation mode over a carbon and a silicon targets in a mixed Ar/N2 atmosphere at a substrate temperature of 300 °C. The substrates were held grounded or at a negative bias of −25 and −50 V. The film characteristics were also controlled by nitrogen flow. Binary and ternary films were obtained. The films were analysed with respect to microstructure, state of chemical bonding and optical properties by Raman spectroscopy (RS) and optical transmittance. RS was used as a probe of micro-structural modifications induced by deposition conditions. The main features observed in RS spectra are the well-known D- and G-bands characteristic of amorphous carbon. The position, widths and intensity ratio of these bands are found to be dependent on the film composition. The refractive index, the absorption coefficient and also the thickness were calculated from transmittance spectra obtained between 200 and 2500 nm. The hardness and Young's modulus of the films were measured by nano-indentation experiments. The average hardness and Young's modulus of the produced coatings was 21 and 200 GPa, respectively.