Superhard titania coatings produced on titanium using induction heat treatment

A review of results of applying the powder technology of self-propagating high-temperature synthesis (SHS) for obtaining various nanomaterials that can be used according to the tribotechnical indentation is given. First, these are low-cost nanopowders of sulfides, oxides, nitrides, carbides, borides, and metals which are suitable as solid lubricants and friction modifiers for liquid and plastic lubricating materials. Second, these are solid compact nanostructured ceramic and composite materials for the fabrication of tribotechnical construction. This type of nanomaterial can be fabricated both ex situ from SHS nanopowders by sintering or introduction into the melt both in situ in one stage from initial powders reagents by gasostatic SHS technology, forced SHS compaction, SHS casting, and SHS in the melt, which considerably simplifies and cheapens the production of such materials. Third, these are SHS materials for the deposition of nanostructured coatings of various thicknesses with a high wear resistance and low friction coefficients, such as nanostructured materials for surfacing and spraying, electrospark alloying electrodes, multicomponent targets for magnetron sputtering, cathodes for vacuum-arc evaporation, and nanodispersed fillers of electrochemical and chemical coatings.

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Nanomaterials of SHS technology for tribological applications: A review

—The intermetallic Ti3Al based alloys with the strengthening boride phases were obtained by the powder metallurgy methods; their composition, structure, and properties were studied. The optimum conditions for thermal treatment allowing obtaining the composite materials of the specified composition with the inclusions of the MAX phase were determined.

Carboborating of the Intermetallic Ti3Al-Based Alloys

This study presents the results of a brief overview on hard and superhard ceramic materials, in particular the crystal lattice parameters and hardness. Their structural parameters were analyzed in order to determine a theoretical dependence describing the hardness changes. A parameter of an effective volume of crystal structure was proposed, which was considered along with the crystal lattice volume and two more indices, i.e. the coordination number and the structural factor. It was shown that the structural factor was determined both for simple substances and for crystals of chemical compounds in which polyatomic molecular complexes were present. A theoretical dependence based on the fundamental relationship between hardness and the deviation of the effective volume of the crystal structure was proposed.

Theoretical dependence of hardness on the structural parameters for hard and superhard ceramics

The phase composition, structure, and properties of self-propagating high-temperature synthesis (SHS)-compacted materials of the Ti-C-Al-Si system are investigated. It is shown that metal-like titanium compounds can be used as cathodes for vacuum-arc evaporators. The coatings fabricated from SHS cathodes are single-phase and represent cubic titanium nitride of the (Ti, Al, Si)N composition. The volume of a microdrop phase in them is smaller by a factor of 2.5–3.0 as compared with TiN, while their microstructure is not fragmented into low-strength columnar elements; the CSR size is twice smaller than that of titanium nitride. Being approximately identically hard, the (Ti, Al, Si)N coatings substantially surpass TiN coatings in elastic and plastic failure resistance due to the lower elasticity modulus. When milling the tungsten-copper alloy, the hardness of hard-alloy milling cutters with the (Ti, Al, Si)N coating is higher by a factor of 2.4 than with the TiN coating fabricated from the titanium cathode with the magnetic plasma flow separation.

Composition, structure, and properties of SHS-compacted cathodes of the Ti-C-Al-Si system and vacuum-arc coatings obtained from them

The results of experiments on the deposition of vacuum-arc Ti-Al-N coatings using aluminum-containing pressed cathodes based on nonstoichiometric titanium carbide TC0.5 are presented. The composition and morphology of coatings are investigated using electron probe microanalysis and scanning electron microscopy. Hardness and elasticity modulus were determined using the nanoindentation method. It is established that carbon is absent in the coating, while the fraction of aluminum in it decreases compared with its content in the cathode material. A superhard coating with nanohardness H = 59 GPa and the Young modulus E = 475 GPa is obtained from the cathode with the calculated composition TiC0.5-30%Al. By the ratio of hardness to the elasticity modulus, which equals H/E = 0.124, this coating is an amorphous-crystalline material. When using cathodes based on refractory nonstoichiometric titanium carbide, the content of the drop phase in coatings substantially lowers with no separation of the plasma flow. In general, the application of multicomponent SHS-compacted cathodes based on nonstoichiometric titanium carbide TiC0.5 makes it possible to fabricate superhard nanocrystalline coatings according to the standard technology using a serial vacuum-arc installation.

V. N. Lavro

Papers

Composition, structure, and properties of SHS-compacted cathodes of the Ti-C-Al-Si system and vacuum-arc coatings obtained from them

Fabrication of vacuum-arc Ti-Al-N coatings using multicomponent SHS-compacted cathodes