V. T. Varchenko

Structure and Properties of Wear-Resistant Spark-Deposited Coatings Produced with a Titanium Carbide Alloy Anode

The paper examines the phase and structure formation during hot pressing of titanium carbide electrode materials as well as the structurization and properties of spark-deposited coatings on steel substrates. The influence of the operating current used for erosion processing on the phase composition and hardness of the coatings is established. It is shown that the electrode materials with a certain composition and structure enable the electrospark deposition of 100 μm-thick coatings with hardness to 14 GPa. The mass of the material deposited on a steel substrate is three times higher than that formed using standard titanium carbide alloy TN20. The wear resistance of the coatings in abrasive and dry sliding friction is high, hence they may be recommended for protection of steel parts for severe wear applications.

Friction and Wear of the TiB2–30 vol.% B4C Composite Consolidated in Spark Plasma Sintering

The tribotechnical properties of the TiB2–30 wt.% B4C composite material in pair with VK6 hard metal are investigated. The material demonstrates high wear resistance under dry friction conditions: the intensity of linear wear of the friction pair does not exceed 1.83 μm/km, the friction coefficient of the friction pair is 0.5. The analysis of 3D profiles of the sample surface shows the effect of smoothing of the surface of the ceramic composite by transfer of hard metal submicron particles on its surface and formation of tribofilm.

Friction and Wear of TiN–Si3N4 Nanocomposites Against ShKh15 Steel

Spark plasma sintering is used to produce dense silicon nitride nanoceramics with titanium nitride additions and nanofiber-strengthened composites. The sintered nanocomposites demonstrate quite high mechanical properties (HV ≈ 14–16 GPa, KIc≈ 4.8 MPa ∙ m1/2) and low dry friction coefficient (f ≈ 0.65–0.68) and mass wear (~0.2–0.4 mg/km) against ShKh15 steel. The nanocomposite strengthened with 3.8 wt.% silicon nitride nanofibers shows the most balanced mechanical and tribotechnical characteristics.

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.

Wear-Resistant High-Temperature Composite Slide Bearings Based on Titanium Aluminides

The structure and properties of composite materials have been studied versus their composition. Comparative analysis of intermetallic titanium materials in dry friction with steel has been carried out. The intermetallic titanium material whose structure is represented by an intermetallic matrix with solid-phase inclusions has the highest tribotechnical properties.

Structure and Mechanical and Tribotechnical Properties of Iron–High-Carbon Ferrochrome Doped with Ni3B Additions

The production conditions and mechanical and tribotechnical properties of iron–high-carbon ferrochrome FKh800 materials doped with nickel boride have been studied. It is shown that Ni3B additions promote the formation of a multiphase microheterogeneous matrix-reinforced structure consisting of chromium steel and solid inclusions of complex chromium–iron carbides such as Me7C3 and Me23C6. When the doping content increases from 3.5 to 7.0 wt.%, complex Fe–Cr carbides and carboborides form, decreasing the hardness and bending strength and increasing the abrasive wear resistance of the base material from 5.0 to 12.2 km/mm. The Fe–35% FKh800 materials containing 5–7 wt.% Ni3B are found to be promising as they combine acceptable mechanical properties and improved abrasive wear resistance.

Effect of the Material and Sliding Rate of the Counterface on the Tribotechnical Properties of a CM(Ti–Mo–BN)–Steel Friction Pair

The effect of the material and sliding rate (1, 2, 4, 6, and 15 m/sec) of the counterface on the tribological characteristics of a (composite Ti–Mo–BN)–counterface (steels 45, 65G, ShKh15, 40Kh, and Kh18N9T, nitrided titanium, and BrO10 bronze) friction pairs in dry friction in air under a pressure of 0.8 MPa is investigated. It is established that, under these friction conditions, the composite in pair with BrO10 bronze is ineffective. During friction of the composite in pairs with steels 45, 65G, ShKh15, 40Kh, and Kh18N9T, an increase in the sliding rate from 1 to 6 m/sec results in an increase of the friction coefficient, linear wear of the friction pairs, mass loss of the composite and counterface, whereas the temperature of the friction surface increases. The highest temperature of the friction surface of the composite is reached in pair with steel 45. The temperature, sliding rate, and pressure applied lead to the synthesis of a secondary film (on the surface of the composite) of such a phase composition and structure that provide (in pair with steel 45) higher tribological characteristics of the composite than those in pairs with the other steels. At all sliding rates of the counterface, the tribological properties of the friction pairs depend not only on the properties of the composite material (chemical and phase composition, structure, and mechanical characteristics), but also on the same properties of the counterface material.

Electrospark-Deposited Coatings from Titanium and Tungsten Carbide Alloys: Mass Transfer Kinetics, Structurization, and Properties

New WC, TiC, and TiB2 electrode materials have been developed for hard wear-resistant electrospark-deposited coatings on a metal substrate. The phase formation and structurization during hot pressing of these materials are studied. The effect of electrode production process on the mass transfer and coating properties is analyzed. The alloys have fine structure with 1–2 μm grains of the major fraction and 26–30 GPa hardness. The structure and functional properties of the electrospark-deposited coatings are examined. Their hardness is 14–24 GPa and thickness 40–120 μm. The new electrode materials show significantly higher scale resistance than T15K6 alloy coatings, and their abrasion and wear resistance in dry friction conditions suggests that they may be efficiently used to strengthen rapidly wearing parts of machines and mechanisms.

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.

Effect of the Deposition Conditions on the Formation of the Microstructure and Properties of (Ti, Zr)N Coating on Chromium Carbide Steels

A complex nitride (Ti, Zr)N coating on chromium carbide steels Kh13M2–30 vol.% Cr3C2and Kh17N2–30 vol.% Cr3C2is obtained. The optimal deposition conditions are determined. The effect of deposition time on the hardness, structure, adhesion strength, and wear resistance of coatings during sliding friction (counterface—steel ShKh15) is investigated. It is established that annealing at 900–1200°C promotes an active interaction of the coating elements with the substrate accompanied by the formation of a transition zone. It is found that the (Ti, Zr)N coatings produced at nitrogen pressure P = 2 Pa, spray-off distance d = 230 mm, and deposition time 30–40 min possess the best mechanical and tribotechnical properties.