The influence of the stirring conditions in the electrolyte on the structure and properties of Ni/Al 2 O 3 nanocomposite coatings was studied. The coatings were produced by electrochemical reduction on a copper substrate in a Watts bath modified by nickel grain inhibitor, cationic surfactant and low concentrated nanometric alumina. The process has been carried out with different types of agitation (mechanical, ultrasonic stirring and with a copper rotating disc electrode). The structures of the produced coatings were characterised by scanning and transmission electron microscopy as well as X-ray diffraction. The influence of Al 2 O 3 particles on the microhardness of composite coatings was also analysed. The adhesion of the composite coatings to the substrate and coefficient of friction were determined by means of the scratch test. The studies have shown that the bath stirring method affects the content and distribution of the alumina, as well as the properties of the produced composite Ni/Al 2 O 3 coatings.
The influence of different types of cemented carbide blades and thickness of TiAlN/a-C:N and TiN/AlTiN protective coatings used in the wood industry on cutting performance has been studied. Three types of WC-Co cemented carbide blades with different cobalt content were used in the study. The thicknesses of both types of coatings were ~2 and ~5 µm. The structure, chemical and phase composition were studied using transmission and scanning electron microscopy (TEM, SEM), X-ray dispersion spectroscopy (EDX) and X-ray diffraction (XRD), respectively. The adhesion was evaluated by scratch test. Nanohardness and durability tests of uncoated and coated blades were performed. We found that the blades covered with 5 µm TiN/AlTiN coatings exhibited the best durability characteristic. The cutting distances were within the range ~6700-~7080 depending on the substrates in comparison with pure substrates (~4300–~4900) and 2 µm TiN/AlTiN coatings (~5400–~6600). The presence of a thin and soft outer a-C:N layer aggravates the nanohardness and durability of the coated blades.
The corrosive properties of PVD TiN-Ti-Al type composite titanium nitride layer with titanium and aluminium sub-layers system on the AZ91D magnesium alloy and its sub-layers were investigated by using polarization method and impedance spectroscopy, specifically, in terms of the hydrothermal tightening effect. The aim was to explain the mechanisms which contribute to high anticorrosive properties obtained by hydrothermal tightening. It was stated that the hydrothermal treatment changes the surface topography of the examined layers, most probably due to the formation of a continuous titanium oxides film. Tightening significantly modifies the corrosion resistance of the particular component sub-layers of the TiN-Ti-Al layer which exhibits optimum electrochemical parameters. It was shown that the increase of the electrochemical parameters is controlled by tightening of the outside titanium nitride layer, whereas the aluminium sub-layer plays a critical role in creating proper conditions for the hydrothermal tightening of titanium nitride.
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