Superhard CrN/MoN films with multilayer architecture

Main regularities of the formation of microstructure and properties ofmultilayer nanostructured CrN/MoN films with periodically changing architecture of layers were considered. Coatings were fabricated by vacuum-arc evaporation of the cathodes (Arc-PVD) in nitrogen atmosphere (pN was 0.4, 0.09 and 0.03 Pa). CrN and γ-Mo2N nitride phases with fcc lattices and a small volume of metastable MoNx cubic phase were formed in the films at pN = 0.4 Pa. The decrease of pN to 0.09 Pa causes the formation of β-Cr2N hexagonal phase. Preferential crystallographic orientation changes from [311] to [111] and [200] when bias voltage Ub is −20, −150 and −300 V respectively. The nanocrystallites size in coatings with bilayer thickness λ = 44 nm decreases to 5.8 nm. The microdeformation grows from 0.4 to 2.3% when Ub changes to −20 V. Coatings show high hardness of 38–42 GPa and H/E = 0.107. In a couple with results of tribological tests, coatings demonstrate strong wear resistance, which makes them appropriate and promising for industrial applications as protective ones. The effect of deposition conditions (pN, Ub, λ) on composition, structure, hardness, toughness and wear resistance was studied to achieve superior mechanical and physical properties of coatings with long lifetime in harsh environment.State budget programs of Ukraine, grant numbers 0116U002621, 0115U000682, 0116U006816; SFRH/BD/ 129614/2017; NORTE-01-0145-FEDER-022096info:eu-repo/semantics/publishedVersio

Struktura i właściwości cienkich warstw międzymetalicznych Al-Cu-Fe nanoszonych metodą wieloźródłowego rozpylania magnetronowego

Thin films of Al-Cu-Fe type have been deposited by means of multisource, DC magnetron sputtering from elemental, metallic targets. The composition of films, studied by the EDS method, has been chosen which is close to the one corresponding to the icosahedral quasicrystalline phase [psi]-Al(62.5)Cu(25.0)Fe(12.5) X-ray diffraction studies of films deposited at 400°C on steel substrates revealed that the cubic [beta]-Al(Cu,Fe) phase is a dominant one. SEM and TEM techniques have been used for the surface and cross section characterisation of deposits. Prolonged post annealing of these coatings led to inter-diffusion of components between the steel substrate and the coating. It leads to the change of the phase composition of the coating and the iron-rich monoclinic [lambda]-Al3Fe1-xCux phase emerges in the film. The preliminary studies of microhardness and tribological behaviour show that the film microhardness reaches a local maximum of about 8.5 GPa for the chemical composition close to the one of the quasicrystalline phase. However, the presence of this phase in studied films has not been proven yet. The friction coefficient values, measured against alumina in ball on disc geometry, oscillate around 0.65 - the value lower than that observed for uncoated 4H13 steel.Cienkie warstwy trójskładnikowe Al-Cu-Fe nanoszono metodą stałoprądowego, wieloźródłowego rozpylania magnetronowego z katod metalicznych. Skład warstw, kontrolowany metodą spektroskopii energodyspersyjnej (EDS) był zbliżony do składu quasi-krystalicznej fazy [psi]-Al(62.5)Cu(25.0)Fe(12.5) o symetrii dwudziestościanu. Struktura warstw nanoszonych przy temperaturze podłoża równej 400°C odpowiadała kubicznej fazie [beta]-Al(Cu,Fe). Morfologię powierzchni warstw oraz ich strukturę badano odpowiednio metodami elektronowej mikroskopii skaningowej (SEM) oraz transmisyjnej mikroskopii elektronuzji składniowej (TEM). Długotrwałe wygrzewanie badanych warstw, nanoszonych na stali prowadzi do dyfuzji żelaza w głąb warstwy, co skutkuje pojawieniem się bogatej w żelazo jednoskośnej fazy [lambda]-Al3Fe1-xCux. Wstępne badania mikrotwardości wskazują na szerokie maksimum na poziomie 8,5 GPa dla warstw o składzie zbliżonym do składu fazy quasi-krystalicznej. Obecność wydzieleń tej fazy w badanych warstwach nie została jeszcze jednoznacznie potwierdzona. Współczynnik tarcia, mierzony względem ceramiki alundowej w układzie kula--płaszczyzna, oscyluje wokół wartości 0,65 i jest niższy niż obserwowany dla niepokrytej stali 4H13

Comparison of ultrasonic and other atomization methods in metal powder production

Purpose The results showed that the UA powder has a finer average particle size with a narrower statistical distribution of particles than those made by the GA method. Because the UA powder has a higher sphericity and lower porosity, Generally, UA offers better-quality powders in terms of properties such as higher tap density, better flowability and low oxygen content. Design/methodology/approach Ultrasonic atomization (UA) with melting raw material by an electric arc. Characterisation of the powders: particle size distribution (PSD), density, and flowability were carried out. Other parameters, such as microstructure, deviation in the chemical composition and powder surface morphology, were also investigated. Findings The results showed that the UA powder has a finer average particle size with a narrower statistical distribution of particles than those made by the GA method. Because the UA powder has a higher sphericity and lower porosity, Generally, UA offers better-quality powders in terms of properties such as higher tap density, better flowability and low oxygen content. Research limitations/implications As an example of semi-industrial scale application of the UA system, the Ti6Al4V and TiAl powders were produced after remelting the wire. The UA system is commercially available for processing any metallic material. Practical implications The test campaign results showed that the Ti6Al4V powder produced by the ultrasonic atomisation has a similar or better quality as those available from large-scale gas atomisation plants. Originality/value The new method of UA powder production was analysed in terms of key powder parameters. The properties of the titanium-based powder produced this way were analysed with a view to future applications

The influence of structure changes in the properties of TiCxOy decorative thin films

The main purpose of this work consists in the preparation of titanium oxycarbide, TiCxOy, thin films, in which the presence of oxygen changed the film properties between those of titanium carbide and those of titanium oxide. Varying the oxide/carbide ratio allowed to tune the structure of the films between titanium oxide and carbide and consequently electronic, mechanical and optical properties of the films. The depositions were carried out from a TiC target by direct current, dc, reactive magnetron sputtering, varying the oxygen flow rate. The obtained results showed that the film's properties can be divided into 3 different regimes -- i) carbide, ii) a transition zone and iii) an oxide one. X-ray diffraction results revealed the occurrence of a face-centered cubic phase (TiC-type) for low oxygen content, also obtained in the TiC1.6(O) film, with a clear tendency towards amorphization with the increase of the oxygen flow rate. For the highest oxygen contents, the results revealed the development of a mixture of poorly crystallized TiO2 phases. The colour results indicated a strong dependence on the O/Ti ratio. A progressive reduction of hardness and residual stresses with the increase of the O/Ti ratio was also observed. The residual stresses, as well as the film structure, seem to play an important role on the adhesion of the coatings. The static friction coefficient revealed also some correlation with the mechanical properties, but mainly with the surface roughness.http://www.sciencedirect.com/science/article/B6TW0-4MWPSDM-2/1/0c4ebbd1524da639df7c8a6dfc51206