I. I. Timofeeva

Production of Ti–Al–Si–B–N Films by Magnetron Sputtering and Study of Their Mechanical Properties

The Ti–Al–Si–B–N films are deposited by dc magnetron sputtering of a composite Ti–Al–Si–B–N target in argon plasma. The structure and phase composition of the films were studied by X-ray diffraction. The chemical bonds in films were examined by X-ray photoelectron spectroscopy. The influence of vacuum annealing on film structure, hardness, and mechanical properties was analyzed. The films deposited at temperatures in the range 200–500°C and bias voltages of 0…–250 exhibited amorphous structure, which was preserved during annealing up to 800°C. At higher annealing temperatures, nanocrystalline phases started to form in the films. Annealing also resulted in increase of hardness and improvement of mechanical characteristics of the films.

DEFORMATION BEHAVIOR OF REFRACTORY METAL CARBIDES DURING RUBBING IN A WIDE TEMPERATURE RANGE

Conclusions1.It is shown that the processes of strengthening (and strength loss) take place in the surface layers of titanium, niobium, and tungsten carbide specimens during high-temperature rubbing in a vacuum are linked with charges in fine crystal structure and phase composition experienced by these carbides in their surface layers.2.It has been established that the strengthening of the surface layers of these carbides observed in the range from room temperature to 400–800°C increases their wear resistance. The strength loss exhibited by the surface layers of the carbides in the range 900–1400°C is a result of the effect of the temperature factor becoming stronger than that of the deformation factor.

Mechanosynthesis of Nanodispersed Titanium Diboride

Structural and morphological changes of titanium during intensive milling of titanium and boron powder mixtures in an AIR-015M planetary-ball mill are investigated. It is shown that the structural transformations in titanium lead to the formation of cluster precipitates (like Guinier–Preston zones) of titanium and boron atoms that are regularly oriented with respect to the titanium lattice and coherently associated with it. Cluster precipitates are very effective nuclei for the further reaction and provide an explosive transition to the almost single-phase titanium diboride. It was found that, in the investigated mechanosynthesis conditions, nanostructured titanium diboride forms in the form of flat and spatial polycrystalline particles, composed of oriented nanograins no larger than 20 nm.

Electric-spark alloying of structural alloys with a composite based on TiCN-AIN

The mass-transfer kinetics, the mechanism of formation, the tribotechnical characteristics, and the resistance to high-temperature oxidation of a coating formed on the hard alloy WC — 6% Co and on the titanium alloy VT6 by electric-spark alloying with electrode material based on TiCN — AIN with an Fe — Cr binder have been investigated. The phase distribution of the components in the coating was shown to be the same for both alloys. Electric-spark alloying of WC — Co and VT6 was found to reduce their wear by 33 and 60%, respectively. Moreover, the working temperature of the coated WC — Co alloy increased by 160 deg compared to the original surface.

Effect of magnetic treatment on the microstructure and abrasive resistance of WC–Co detonation-sprayed coatings

The effect of magnetic field on the phase composition and mechanical properties of VK-9 and VK-15 hardmetal detonation-sprayed coatings is studied. It is established that the magnetic field induces phase and structural transformations in sprayed coatings, such as reinforcement of the Co matrix due to the dissolution of WC in Co and the formation of WxCoyCz binary carbides. Magnetic treatment reduces residual internal stresses in the coating, decreases the amorphicity of its structure, and increases abrasive wear resistance.

Influence of the Structure and Properties OF WC – Co Alloy Powders on the Structure and Wear-Resistance of Detonation Coatings

We have made comparative investigations of the structure, phase composition and abrasive wear resistance of WC – Co coatings sprayed by the detonation method using powders of identical chemical composition and different particle structure, because the powders are prepared by different technologies. The laws we have found that govern how the structure evolves from the initial powder to a coating allow us to predict the physicotechnical properties of the coating. The more porous the powders, the more they are affected by the gas atmosphere in the spraying process and thus, the more significant changes in the phase composition are observed in the powder – coating system. The use of powders with highly porous particles results in the formation of porous coatings with low wear resistance.

Mechanical activation of the reactive sintering of titanium carbide

This paper describes the mechanical alloying of Ti and C powders by intensive grinding in a planetary mill. The effect of milling conditions and initial composition on the compositional homogeneity and properties of powders and samples consolidated by hot-pressing was studied by x-ray diffraction, scanning electron microscopy, and surface area measurement. The diffraction patterns indicated that a powder mixture ground for 24 hours transforms to TiC after sintering for only one minute at 600°C under a pressure of 3 GPa.

Effect of Coating Deposition Methods on the Properties of Titanium Aluminide Materials

The behavior of detonation and plasma coatings in conditions of dry friction against titanium alloy OT-4 and stainless steel 07Kh16N6 has been studied. The detonation coatings show significantly better tribological properties than the plasma coatings. This is probably due to the presence of aluminum and titanium nitrides possessing high wear resistance in the detonation coatings. Oxidation of the plasma and detonation coatings at a temperature of 900°C in air has been examined. The detonation and plasma coatings exhibit greater oxidation resistance than uncoated titanium alloy VT-16.

Structural and Phase Transformations in Fe–Al Intermetallic Powders During Mechanochemical Sintering

The paper examines the structural and phase transformations in Fe–Al powders after mechanochemical sintering followed by heat treatment. The intermetallics are sintered through a series of successive stages, each resulting in a nanosized product. The amount of energy required for the formation of a single-phase intermetallic compound increases with aluminum content of the intermetallic phase (from Fe3Al to FeAl and then to Fe2Al5).

Formation of Diborides of Groups IV–VI Transition Metals During Mechanochemical Synthesis

Fine powders of diborides of groups IV–VI transition metals (TiB2, HfB2, NbB2, TaB2, CrB2, Mo2B5, and W2B5) were produced by mechanochemical synthesis and low-temperature heat treatment of activated charges. The particle size of the powders was ≤1 μm. It is revealed that processes of formation of diborides of groups IV–VI transition metals differ within period and group. Diborides Ti and Nb formed discontinuously. Diborides Hf and Ta formed after the formation of lower boride phases, whereas higher borides Cr, Mo, and W formed in almost a single-phase state only after a low-temperature treatment of preliminarily mechanoactivated charges. The differences were analyzed from the point of view of the donor-acceptor capacity of the atoms of boron and diboride-forming transition metals.