A. D. Kostenko

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.

Prospects of Improving the Tribotechnical Characteristics of Titanium Composites

Titanium-based composites containing MoS2, MoSe2, CaF2, and BN solid lubricants are synthesized. Their tribological characteristics are investigated without lubrication at different sliding velocities (0.5, 1, 2, 4, 6, and 15 m/sec) and low pressures (0.27, 0.54, 0.8, 1.1, 1.35, 1.47, and 2.7 MPa) in air. In view of the high friction coefficient and large wear, the composite materials cannot be proposed as antifriction ones for operation at small sliding velocities and low pressures. The titanium-based composites are promising as antifriction materials at an increased sliding velocity (15 m/sec) and low pressures when their friction coefficients range from 0.3 to 0.36 and wear ranges from 1.91 to 68.3 mg/km. In dry friction at a high sliding velocity in air, the temperature of their working surface increases resulting from the formation of titanium oxides and then a dense secondary lubricating microheterogeneous film. The composition and structure of the secondary films differ from those of the starting materials and determine their antifriction properties and friction performance.

Effect of the composition and structure of silicon carbide composites on wear mechanisms

The tribotechnical characteristics of SiC–Al2O3 and SiC–Al2O3–ZrO2 ceramic composites are studied during dry plane-on-plane friction in a wide range of velocities (2–7 m/sec) and loadings (1– 7 MPa). This testing pattern allows modeling the performance of composites as sealing elements for centrifugal pumps. The influence of 20, 50, and 80 wt.% aluminum oxide in silicon carbide on the wear rate and wear mechanisms is analyzed. It is shown that higher alumina content of the SiC–Al2O3 ceramics changes the wear mechanisms: oxidative–adhesive wear takes place in materials containing 20 wt.% Al2O3 and mechanochemical wear in SiC–80 wt.% Al2O3. The tribotechnical characteristics of SiC–Al2O3–ZrO2 (SIAL-Z) ceramics have been studied. The ratio of aluminum and zirconium oxides in this material is eutectic, which substantially decreases the hot pressing temperature and promotes a fine-grained structure. Oxidative wear takes place in friction of the SIAL-Z ceramics against a steel counterface. This composite has the highest tribotechnical characteristics among the materials of interest.

Wear Resistance of High-Entropy Alloys

The tribotechnical properties of high-entropy alloys in pair with 65G steel in air under dry sliding friction conditions are investigated in comparison with wear-resistant steel and powder materials. The sliding friction rate was 6, 8, and 12 m/sec and the pressure was 0.5 and 1.0 MPa. It is determined that the wear intensity of high-entropy alloys at the sliding friction rate 5–10 m/sec under 0.5 and 1.0 MPa loads ranges from 6.1 · 10–10 g/km to 1.6 · 10–9 g/km for the samples and from 5.5 · 10–8 g/km to 1.1 · 10–8 g/km for the counterface. It is established that, when friction, the shear deformations promote the formation of thermally stable nanostructures with grains 30–70 nm in size in the surface layer of the secondary structures. It is shown that the formation of nanostructures is accompanied with 20–30% increase in hardness for both high-entropy alloys and counterface material. It is established that, when friction, high temperatures at the contact points promote the formation of ordered β-phase with BCC lattice on the friction surface of the Fe25Cr20Ni20 Mn15Co10Al10 high-entropy alloy.

The Mechanical Properties of Sialon–Boron Nitride Composite Ceramics

The production of sialon and sialon–boron nitride composites using oxidized (up to ~15 wt.% O) Si3N4–18 wt.% AlN composite powders resulting from plasma chemical synthesis is studied. Hot pressing of these powders to nonporous state at 1620–1775°C is accompanied by the formation of composites consisting mainly of a mixture of β-sialon (z = 1.5–2) and o′-sialon. Boron nitride additions in an amount of up to 15 wt.% lead to the formation of composites that contain BN lamellar grains in the matrix of single-phase β-sialon (z = 1.5–2). The mechanical and tribological characteristics of the composites with micron and submicron grains are examined. It is observed that the dependence of scratch hardness on contact strength is almost linear for the sialon ceramics and sialon–boron nitride composites. The material is removed during machining through intensive brittle fracture. The introduction of boron nitride into sialon ceramics in an amount of more than 5% is accompanied by approximately a tenfold increase in the material removal in machining, making possible turning operations.

Tribotechnical Characteristics of Superhard Boron Nitride-Based Materials During Dry Friction of Like Pairs

Friction units are made of superhard cubic boron nitride-based materials by vacuum brazing and subjected to end-to-end dry friction testing. It is established that the friction factor decreases as the modulus of elasticity of superhard material is decreased and the loading and friction speed are increased.

Tribological Characteristics of the Iron-Based Composite at 500°C

The tribological characteristics of the Fe–W–CaF2 composite antifriction material (CAM) in combination with 1Kh18N9T steel are examined in air at a temperature of 500°C, a pressure of 0.8 to 3.3 MPa, and a sliding velocity of 0.5–2.0 m/sec. It is established that the friction coefficient, mass wear Im, and linear wear Il of the composite decrease, respectively, from 0.3 to 0.26, from 5 to 2 mg/km, and from 30 to <5 μm/km at constant pressure (0.8 MPa) with increase in the sliding velocity from 0.5 to 2 m/sec. At a constant sliding velocity (0.5 m/sec), with increase in pressure on the tribological system from 0.8 to 3.3 MPa, the friction coefficient f decreases from 0.3 to 0.26, whereas its mass wear Im and linear wear Il increase from 5 to 8.4 mg/km and from 30 to 57 μm/km. It is shown that secondary lubricating films form in friction on the working surface of the material. Like the starting material, they have a microheterogeneous structure and determine antifriction properties. The bcc solid solution of tungsten in α-iron hardened by inclusions of iron tungstate is a bearing structural component of the secondary lubricating films, and inclusions of iron oxides and calcium fluoride are antifriction structural components. The presence and content of the phases as well as the percentage of structural (antifriction and bearing) components in the secondary lubricating films depend on friction conditions (P · V). With increasing amount of the bearing structural component in the secondary film, wear of the material decreases. Higher content of the antifriction structural component in the film decreases the friction coefficient of the material.

Wear-Resistant Heterophase Fe–Si–B–C Powder Materials

The microstructure, mechanical characteristics, and tribological properties of Fe–Si–B–C powder composites are analyzed to determine scientific and engineering principles for their production by single pressing and sintering followed by heat treatment. The composites have heterophase structure and can be recommended for wear-resistant parts for dry friction applications.