Tribotechnical Characteristics Research Articles

Modification of working surface of titanium components of friction units

The paper addresses the possibility of using titanium in friction units of artificial joints. Tribotechnical characteristics of titanium–hirulen friction couple is studied. The authors put forward a technology of surface cold plastic deformation (SCPD) of spherical components and thermodiffusion nitriding of spherical pure titanium heads for human hip implants. SCPD is shown to provide a higher level of surface hardening, which makes the curves of microhardness distribution in the cross-section of hardened surface layers shift towards higher hardness values. The surface microhardness (at a depth of about 5 μm) of the nitrided layer of SCPD-worked specimens significantly exceeds (by up to 30%) that of non-worked specimens.

Impact of Modification Process on Graphite Structure at Application of Chloroperfluorododecylfluoro Sulfate

Impact of the process of modification on graphite structure at the application of fluorine-containing oligomer-FDS (chloroperfluorododecylfluoro sulfate) has been studied. It was shown that during this process graphite structure does not change. Only particles of FDS are destructed into monolayers, which are spread in graphite intercrystalline voids. At the mechanical impact it protects graphite from destruction and correspondingly, improveing some of its tribotechnical characteristics.

Studies of the structure, physicochemical properties and tribotechnical characteristics of composite materials of the NiAl–ZrB2 system

The wetting and special features of the contact interactions in the NiAl–ZrB2 system have been studied. The phase and chemical compositions of the interaction products have been analyzed. The structures and properties of composite materials of the above system and coatings made of them, which are designed to protect the components of gas-turbine engines operating at high temperatures and loads, have been investigated. The friction surfaces of the NiAl and NiAl–15 ZrB2 developed plasma coatings have been also considered. The oxides formed on the friction surfaces have been shown to play the role of a solid lubricant. It has been found that the wear behavior and intensity are essentially affected by the tribo-testing temperature and the presence of a reinforcing boride phase.

Experimental studies of tribotechnical characteristics of radiation-modified polytetrafluoroethylene to use in rotor supports

The tribotechnical characteristics of radiation-modified polytetrafluoroethylene (PTFE) are studied at specific pressures of 10–20 MPa that correspond to the working conditions in the supports of engine rotors. It is shown that a mean coefficient of sliding friction of the modified PTEE is much lower than that of the normal PTFE, while the intensity of surface wear of the modified PTEE is two orders of magnitude less than that of the normal PTFE.

Friction of high-entropy Fe25Cr20Ni20Mn15Co10Al10 alloy for 65G steel

The tribotechnical characteristics of Fe25Cr20Ni20Mn15Co10Al10 high-entropy alloy paired with 65G steel on the air without grease were investigated. Friction took place in the range of speeds of 6–12 m/s and pressures of 0.5 and 1 MPa. Research of the friction characteristics without grease was also carried out at 0.07 m/s. It was determined that the coefficient of the wear rate of the high-entropy alloy varies from 6 × 10−10 to 2 × 10−9 kg/m3 during counterface wear from 5.5 × 10−8 to 2.2 × 10−9 kg/m3. It has been shown that the deformation of shear friction led to the formation of thermally stable nanostructures with size of grains about 30–70 nm in the surface layer of secondary structures. Hardness of secondary structures is increased by 20–30% both in high-entropy alloy and the material of the counterbody.

Structure and Tribotechnical Characteristics of NiAl–CrB2 Composite Materials and Coatings

The influence of chromium diboride additions on the tribotechnical characteristics of NiAl–CrB2 composite coatings in friction against a counterface made of NiAl plasma-sprayed coating is studied. The friction surfaces of the plasma-sprayed composite NiAl coatings with different chromium diboride contents (5, 15, and 30 wt.%) are examined. It is established that wear substantially depends on the amount of refractory component.

Wear resistance of composites based on hybrid UHMWPE–PTFE matrix: Mechanical and tribotechnical properties of the matrix

In order to develop biocompatible antifriction composites based on UHMWPE the mechanical and tribotechnical characteristics of a hybrid polymer matrix in the form of a mixture (blend) of UHMWPE with polytetrafluoroethylene (PTFE) have been studied under dry friction, boundary lubrication, and abrasive wear. It has been shown that the wear rate of the material under dry sliding friction was reduced more than twofold compared with pure UHMWPE. However, the mechanical characteristics have changed insignificantly. Under the boundary lubrication (distilled water), the wear resistance of the matrix material is similar to that for dry sliding friction. Under abrasive wear, the durability of the composites differs a little from that for pure UHMWPE. The mechanisms of wear of the polymer blend UHMWPE–PTFE under dry sliding friction and abrasive wear have been discussed.

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.

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, K Ic ≈ 4.8 MPa ∙ m 1/2 ) 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.

The Effect of Molybdenum Disulphide on the Tribotechnical Characteristics of Polyamide Coatings on Nitrile Rubber Compounds

The Effect of Molybdenum Disulphide on the Tribotechnical Characteristics of Polyamide Coatings on Nitrile Rubber Compounds

Change of Structure and Properties of Sintered Alloys under the Influence Nanosized Carbon Additives

There was considered influence of nanosized carbon additives on structural phase state and properties of the sintered alloys on the copper, iron and tungsten-cobalt base. There was demonstrated that under liquid phase sintering and crystallization process of powder compositions that contain nanosized carbon particles. non-dissolved fraction of nanosized additive could be stands as additional nucleation centers, that promotes atomization of structure. There was established that for alloys that could be form solid solutions with carbon or hardening carbide phases. nanosized diamond- graphite additives increase of hardness of sintered composites and improve its tribotechnical characteristics

Vermiculite-based organosilicate antifriction composites as coatings on friction surfaces of steel articles

Influence exerted by modification of vermiculite on the tribotechnical characteristics of oil additives was studied. The wear rates were compared for additives containing polytetrafluoroethylene and vermiculite treated with 5–7% hydrochloric acid, followed by modification with polytetrafluoroethylene, and vermiculites modified with chitosan and polyphenylsiloxane. The wear rate was studied in three stages: first (application of an additive), 3 min; second (formation of a coating), 60 min; and third (tribotests), 180 min. Polytetrafluoroethylene and vermiculite modified with polytetrafluoroethylene were compared. It is shown that introduction of polyphenylsiloxane on the vermiculite surface leads to a sharp decrease in the wear rate in the second and third stages. The worn-out oil was analyzed and the formation of a metal-siloxane coating was confirmed. The mechanical and morphological characteristics of the films formed on friction surfaces were studied. The best results were obtained for coatings with an additive containing polyphenylsiloxane.

Tribotechnical properties of electrospark coatings of amorphous and nanocrystalline iron alloys

The tribotechnical characteristics of electrospark coatings of amorphous and nanocrystalline iron alloys have been determined. The influence of the crystalline phase on the wear rate of electrospark coating has been established.

APPLICATION OF CLUSTER ANALYSIS IN SELECTION AND DEVELOPMENT OF COMPLEX-ACTION DRILLING MUD ADDITIVES

Introduction of chemical compounds into drilling mud as complex-action additives is the most available, easy to implement and efficient method to improve technical-and-economic indexes of drilling. Selection and development of complex-action additives, as well as rapid selection of chemical compounds to be used as effective complex-action additives, are important tasks today. The article presents the possibility of using electrochemical and multidimensional statistical data analyses to improve selection of the additives obtained on the basis of a wide variety of compounds enhancing drilling mud resistance to corrosion and tribotechnical characteristics. Drilling mud tribotechnical characteristics were analyzed with the use of the modified AI-3M friction and wear testing machine manufactured in accordance with the “disk-rock” wear scheme. Drilling mud resistance to corrosion was analyzed by electrochemical methods. The method is based on recording the steel cyclic voltammetric curves (cyclic voltammetry method) in the analyzed liquid medium. Local metal surface damage formation – repair dynamics was also monitored by galvanodynamic method. To process the data obtained, cluster analysis was used making it possible to divide all the solutions into three groups (I, II и III). This significantly simplified the processing of the results, helped to reject the poorest additive compositions and identify unobvious relationship between drilling mud anticorrosion and tribotechnical characteristics in the groups. Thus, the proposed method makes it possible to considerably reduce working hours of selection and development of complex-action additives, as well as improve the validity of the results obtained. The proposed methodological approach for selection and development of complex-action additives allows rejection of inefficient prototypes by the most rapid and natural way.

Tribological characteristics of (TiZrHfVNbTa)N coatings applied using the vacuum arc deposition method

The effect of the pressure of the nitrogen atmosphere during the formation of vacuum arc nitride coatings based on high entropy alloys of the Ti-Zr-Hf-V-Nb-Ta system on their structure, hardness, and tribotechnical characteristics is considered. It is shown that strong nitride-forming components lead to the dependence of the structural state and properties on the pressure of the nitrogen atmosphere during coating deposition. Deposition at a nitrogen pressure of 0.4 Pa results in the formation of a texture with the [111] axis when the applied bias potential is −70 V and when the bias potential is equal to −150 V the textural structure is biaxial ([111] and [110]) textures and high value of hardness of 51 GPa Along with that the highest value of wear resistance (under oxidizing-mechanical wear) is inherent to coatings formed under the pressure of nitrogen of 0.09 Pa. The strongest microdeformation of coating crystallites corresponds to this pressure.

BRUSH SEALS FOR GAS-DYNAMIC INSTALLATIONS

The creation of a new generation of gas turbine equipment should be provided as one of the most important issues is the provision of high reliability and tightness of sealing gap between stator and rotor. In gas-dynamic installations this is considered to be one of the promising ways to increase their efficiency by reducing losses in the gas path. The presence of a gas leak from areas of high pressure to an area of low pressure is extremely undesirable, reducing the efficiency of the turbine and leading to increase of fuel consumption. To reduce the flow of gas between the body of the gas-dynamic installations and end surfaces of the blades of the turbine radial clearance should be minimal. The experience of recent decades has shown the feasibility of using seals brush type. Almost all promising developments gas turbines for sealing joints are used brush seals. This article presents the results of laboratory research of a new, composite brush seal for gas turbine unit blades. Proposed sealing strips is performed by the method of electrochemical etching directly on the end of the pen blades. This option is the location of the brush seals allowed to extend its functionality and use the brush seals in contact with prerelativity seal. Contact elements brush seal, is pressed their ends to the internal surface of the stator, provide high quality sealing gap. The bristles seals are made integral with the pen blades are strictly regular distribution on the surface of the end face, which remain in operation. Manufacturing technology brush seals on the end of the blades provides for the possibility of using the actual brush seals or brush seals with filler. The last option allows you to combine the positive effects prerelativity and brush seals. The study of tribotechnical characteristics of the seals has shown that the suggested seals have higher operating characteristics compared with the conventional seals. The brush seal was developed and studied at LLC "Turbinepowered" together with the Ufa state aviation technical University.

Effect of the Chemical Composition of Electrode Materials and Deposition Conditions on the Properties of Spark-Deposited Coatings. II. Coating Hardness and Wear Resistance

Cermet coatings based on Ni–Al alloys and titanium–chromium diboride are electrospark-deposited onto 40Kh steel. It is analyzed how the metal-to-refractory phase ratio in the electrode material and the deposition conditions influence the mechanical and tribotechnical characteristics of the coatings. The wear resistance and friction coefficients of the electrospark-deposited coatings are shown to depend on the friction speed and loading. The cermet coatings show high tribotechnical characteristics (I = 1–5 μm/km, f = 0.2–0.25) at speeds to 12 m/sec and loads to 4 MPa in dry friction conditions. These characteristics can be controlled by varying electrode chemical composition and deposition conditions.

Experimental study of the speed-dependence tribotechnical characteristics of some plasma-sprayed oxide coatings at elevated temperatures

The effect of the sliding speed on friction and wear characteristics of plasma-sprayed ceramic coatings (Al2O3-13% TiO2, ZrO2-8% Y2O3, Al2O3-modified) was studied. Plasma-sprayed coatings are not hard and have high layered structure. Abrasion of coatings in the friction pair with steel and bronze counter-bodies occurs through brittle detachment conglomerated regions with low cohesive resistance. The modified coating (Al2O3) has the highest wear resistance and the lower coefficient of friction compared to the coatings (Al2O3-13% TiO2, ZrO2-8% Y2O3) in the studied velocity range (0.1–10 mm/s). Laser melting can be used as an efficient way of increasing the tribotechnical properties of plasma-sprayed oxide coatings.

‘Fluoroplastic–Multi-Walled Carbon Nanotube’ Composites: Structural, Mechanical, and Tribotechnical Characteristics

The paper studies the production of ‘fluoroplastic–carbon nanotube’ composites, analyzes their structure, and determines their mechanical and tribotechnical characteristics. The properties of the composites depending on the reinforcement content are examined. It is established that addition of only 3% carbon nanotubes significantly increases the hardness and Young’s modulus while the wear becomes two orders of magnitude lower under friction without lubrication. The structure of ‘fluoroplastic–carbon nanotube’ composites is analyzed in detail. A mechanism whereby carbon nanotubes influence the mechanical characteristics and wear resistance is proposed.

Tribotechnical properties of powder hard alloys of chromium carbide with titanium fabricated by explosive pressing

Tribotechnical characteristics of the Ti-Cr-system hard alloys produced by the explosive compaction of powders containing 20, 30, 40, and 50 vol % of the titanium binder are investigated. The general approach to selecting the optimal structure and properties of wear-resistant hard alloys for manufacturing the slider bearing parts working in pair with silicicated graphite in conditions of water lubrication is formulated. It is shown that, in order to attain the highest antifriction characteristics and minimal wear of the friction unit, the alloy should have the maximally possible hardness with the minimally admissible specific volume of a carbide phase in the material structure. It is established that the mentioned alloys have higher antifriction characteristics and wear resistance than silicicated graphite and the Cr3C2-20% Ni-type materials produced by conventional methods.