Composite Antifriction Material Research Articles

Composite Antifriction Material Based on Wastes of Aluminum Alloy for Items of Post-Printing Equipment

Composite Antifriction Material Based on Wastes of Aluminum Alloy for Items of Post-Printing Equipment

Friction Mechanism Features of the Nickel-Based Composite Antifriction Materials at High Temperatures

The friction behavior of the formed antifriction films and their effect on the functional properties of the composite based on the powder nickel alloy EI929 with solid lubricant CaF2 at high temperatures was investigated. An antifriction film was formed on the contact surfaces during the friction process. Such a film was the result of the interaction of the contact surfaces with atmospheric oxygen at high temperatures. It contains oxides of alloying elements from materials of the frictional contact and solid lubricant calcium fluoride. The quantitative ratio of formed oxides depends on the temperature operating conditions of material. The data of thermodynamic simulation of the high-temperature interaction of the composite with oxygen coincide with the experimental data obtained by studying the fine structure of surface antifriction films. Antifriction films consist of oxide phases in combination with solid CaF2 lubricant. Anti-friction films provide high wear resistance of the self-lubricating composite in the range of temperatures 1073–1173 K due to the balance between the rate of their formation and wear. When the temperature exceeds 1200 K, the film loses its lubricating properties and acts as an abrasive substance due to the intense oxidation. Abrasive surfaces of materials were subjected also to microscopic examination, in which the mechanically mixed layer (MML) was described. The study of the friction surface roughness parameters confirmed the presence of the formed friction self-lubricating film and allowed to determine its parameters. The friction mechanism was the formation of an oxide layer combined with a solid lubricant, which provides high antifriction properties in the range of 1073–1273 K.

STRUCTURE AND TRIBOTECHNICAL PROPERTIES OF COMPOSITE ANTIFRICTION MATERIALS BASED ON R7M2F6 STEEL WASTE

Background. Development of the technological measures for creating new antifriction composite materials based on waste powders of steel P7M2F6 with solid lubricant CaF2, intended for operation at temperatures up to 600 °C, sliding speeds up to 1 m/s, loads up to 5.0 MPa in air.Objective. The purpose of the paper is to determine the features of structure formation and their influence on the properties of composite antifriction materials based on industrial grinding waste of steel P7M2F6 with solid lubricant CaF2 for operation at high temperature friction units in air.Methods. Methodology consisted of the development of the regeneration technological modes of the industrial grinding waste of steel P7M2F6, determination of technological manufacturing operations for new antifriction composites that include mixing of steel powders with solid lubricant, pressing and sintering of composites. The study of the structure formation processes and properties of materials was carried out using optical and electron microscopy methods, standard methods for determining mechanical properties and tests for friction and wear.Results. The influence of the developed manufacturing technology on the formation of the structure, physical mechanical and tribotechnical properties of materials based on steel P7M2F6 grinding waste with solid lubricant CaF2 additives was determined and grounded; resulting is the formation of complex heterogeneous antifriction material with high functional characteristics. The new material’s structure formation and its influence on the functional properties after using the developed manufacture modes was shown. Micro-X-ray spectral analysis confirmed the fact that CaF2, the contact pair’s chemical elements and oxygen form an antifriction film that provides a self-lubrication mode at the determined friction temperatures.Conclusions. The possibility of predicting the structure and functional properties of antifriction self-lubricating composite materials at high temperatures by purposeful choice of starting metal grinding wastes for certain operation conditions of contact pair was shown.

Some Features of Bearing Units’ Development Based on Sliding Friction Pairs for Precision Electrospindles

In mechanical engineering, various types of bearing units are used in moving connections and sliding pairs (sliding bearings, guides, bushings) are sufficiently widely used. This allows increasing the stiffness of the units, reducing their dimensions, improving heat dissipation, etc. But there are higher friction losses, probability in the increases of situations in which there is a jamming of friction surfaces for application of sliding friction pairs compared to the rolling bearings. These problems are even more important for application of sliding bearings in precision equipment, which typically operates under temperature and humidity stabilized conditions. The aim of the work is the development of methodological approaches to the creation and rational design and manufacture of sliding friction pairs based on the composite antifriction materials’ coatings for the application in vertical precision program-controlled electrospindles for high-speed machining. Questions of development and manufacturing of friction units for precision electrospindles with high rigidity on the basis of composite materials are considered. It is shown that acceptable cutting speed (750 m/min or more) for the quality standpoint of processing with a diamond-like tool can be achieved by placing the cutting edge of the tool on diameter of 200 mm. As a result, two tasks solved: the rigidity of the electrospindle for ultra-high accuracy of mechanical blade processing is achieved; high smoothness of work is provided, which allows achieving nanometric surface roughness with a decrease of deviations to 1 µm from the middle surface line. It is extremely important for a number of special applications.

Formation of sylicides of aluminium in the Al-Si-Ti system

Currently used discrete fillers of cast aluminum matrix composite antifriction materials in most cases are characterized by high hardness, leading to increased wear of steel pairs of friction, which makes the search for new fillers urgent. Due to the formation of titanium aluminosilicates in the Al-Ti-Si system and the insignificant solubility of silicon and titanium in aluminum, it was suggested that it is possible to obtain composite materials based on them by the in-situ method or by synthesizing reinforcing materials in a liquid metal matrix. The introduction of titanium in the amount of 10 wt. % into the melts of Al-10÷20 wt. % Si at 700, 800 and 900 °C and subsequent isothermal holding the composite materials are synthesized. By melting in the range of 1000-1100 °C the Al-10÷25 wt. % Si-5÷15 wt. % Ti materials are obtained The phase composition of these materials and the content of elements in the primary phases formed in the aluminum matrix, the hardness of materials obtained by melting is determined. Studies of the formation of phases in the Al-Si-Ti system showed that under the conditions of their synthesis in the liquid phase as a result of reaction-diffusion, a large spectrum of aluminosilicates is formed, which are characterized by a dispersed structure. Under such conditions, since the processes are far from equilibrium, the formation of phases that cannot form during crystallization from the melt under conditions of its cooling is possible. This makes it possible, by varying the synthesis temperature and composition of the charge materials, in wide intervals, to change the properties of the resulting aluminum-matrix composite materials. Similar composite alloys that form during crystallization from the melt are characterized by a more coarse-crystalline structure and a substantially smaller spectrum of silicides, which obviously impairs their properties. The tests of the composite material of composition 85 % Al-15 % Si – 10 % Ti for friction-wear showed that it is characterized by high tribological characteristics. A significant advantage of the materials of the Al-Si-Ti system is the absence of solid phases capable of damaging the surface of the counter body made of steel. This makes promising further studies of the tribotechnical characteristics of the composites of this system.

Features of Structure Formation and Properties of Com¬posite Antifriction Materials for Printing Machines Based on Recovered Wastes

Background. Development of the technological measures for creating new antifriction composite materials based on industrial grinding waste of steel 2Х6В8М2К7 with solid lubricant CaF 2 , and also the technological possibilities expansion of using a wider range of valuable secondary raw materials for the synthesis of qualitative structural materials. Objective. The aim of the paper is to determine the features of structure formation and their influence on the properties of composite antifriction materials based on industrial grinding waste of steel 2Х6В8М2К7 with solid lubricant CaF 2 designed for the printing machine’s friction unit in conditions of self-lubrication at speeds up to 750 rpm and loads up to 8.0 MPa in the air. Methods. Development of the recovery technological modes of the industrial grinding waste of steel 2Х6В8М2К7; determination of technological manufacturing operations for new antifriction composites that include mixing of steel powders with solid lubricant, pressing and sintering of composites. The study of the structure formation processes and properties of materials was carried out using optical and electron microscopy methods, standard methods for determining mechanical properties and tests for friction and wear. Results. The influence of the developed manufacturing technology on the structure formation, physicomechanical and tribotechnical properties of materials based on steel 2Х6В8М2К7 grinding waste with solid lubricant CaF 2 was determined and grounded, resulting in the formation of complex heterogeneous antifriction material with high functional characteristics. Conclusions. The possibility to control the structure and functional properties of composite antifriction materials based on steel 2Х6В8М2К7 grinding waste with solid lubricant CaF 2 for the printing machines’ parts by technological means, selecting the appropriate mark of metal grinding waste depending on the purpose of the part, the solid lubricant quantitative variations, and to apply rational manufacturing technological modes for obtaining a predetermined structure and predicted level of functional properties are grounded.

Interaction of Structural Components of Titanium Composite in Vacuum at 1150°C

The interaction of a Ti + 10 Mo titanium alloy, which serves as a matrix in a tribological material, with calcium fluoride CaF2 and boron nitride BN, which play the role of a solid lubricant, during their heating and sintering in a vacuum of 10–3 Pa at 1150°C for 15 and 120 min, respectively, has been studied. In the heating of a Ti + 10 Mo + CaF2 model sample for 15 min and sintering of Ti + 10 Mo + CaF2 CAM1 for 120 min, calcium fluoride does not interact with the Ti + 10 Mo matrix and does not change its composition and structure; a transition layer between the matrix and solid lubricant does not form. Thus, calcium fluoride preserves its initial lubricating properties. In the sintering of Ti + 10 Mo + 13 CaF2 CAM1 for 120 min, a composite antifriction material with a microheterogeneous structure is synthesized. Its structure is a mixture of solid solutions of molybdenum in α- and β-titanium, which has a body-centered cubic lattice and face-centered hexagonal lattice, in which calcium fluoride CaF2 is distributed in the form of inclusions. In the heating of a Ti + 10 Mo + BN model sample for 15 min and sintering of Ti + 10 Mo + BN CAM2 for 120 min, the interaction of the Ti+10Mo alloy with boron nitride BN occurs to form a transition layer with the phase composition α-TiMo + TiB + TiN + BN. In the sintering of Ti + 10 Mo + BN CAM2 for 120 min, a composite material with a microheterogeneous structure is synthesized. Its structure is a solid solution of Mo in α-Ti with a face-centered hexagonal lattice, strengthened by products of interaction of titanium with nitrogen and boron, TiN and TiB, in which boron nitride BN is distributed in the form of inclusions.

Improving the Reliability of Hinge Joint Oil Pumps

Improvements in the reliability of friction units by using polymer composite antifriction materials modified with various fillers, including nanoscale ones, are considered.

Formation of an Intermetallic Layer during Arc Facing of Aluminum Alloys onto a Steel Substrate

Aluminum alloys, the composition of which is close to the matrix alloy of a composite antifriction materials, are deposited onto a steel substrate with a 10-μm-thick zinc coating. An aluminum coating on a steel substrate is formed by manual argon-arc facing with a nonconsumable electrode, arc facing using the cold metal transfer technology, and the technology that combined these methods with remelting of the first layer. The influence of the rate of energy input in facing and the alloying elements in a filler material (silicon is used as an example) on the kinetics of formation and growth of an intermetallic layer at the interface during the deposition of an aluminum layer onto a steel substrate is studied.

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.

Effect of dry friction parameters on the tribosynthesis of secondary structures on composite antifriction iron-based material

The paper examines the tribological characteristics of a Fe–W–CaF2 composite antifriction material (CAM) in combination with 65G steel during dry friction in air at a high sliding velocity (15 m/sec) and insignificant (0.64–1.28 MPa) pressures. It is established that with twofold increase in pressure (from 0.64 to 1.28 MPa), CAM friction coefficient decreases from 0.25 to 0.20 (by 20%) and wear increases from 0.0158 to 0.03085 mg/km (by 49%) but remains insignificant. The factors acting in the friction process lead to the formation of secondary lubricating films. They prevent mechanical contact between the rubbing surfaces and provide necessary antifriction and operating properties. It is shown that the secondary lubricating films as thin layers with inclusions of solid lubricants differ from the starting material in chemical and phase composition, structural state, and better mechanical characteristics.

Service properties of Cu–Sn–CuWO4–MoS2 composite and micromechanical characteristics of its friction surface

The paper examines the tribotechnical characteristics of the Cu–Sn–CuWO4–MoS2 antifriction composite during lubricated and dry friction at sliding speeds 0.5, 1, and 1.5 m/sec. X-ray diffraction of the material and its friction surfaces is conducted and their micromechanical characteristics are determined. The mechanism whereby the composite antifriction material attains the optimal tribotechnical characteristics is explained. It is established that the friction coefficient and wear rate of the composite depend, under varying friction parameters, on changes in the composition, structure, and micromechanical characteristics of the friction surface.

Copper tungstate produced from tungsten-containing waste as addition to antifriction material

The paper examines the use of tungsten-containing waste to develop a copper-based microheterogeneous antifriction material. The effect of copper tungstate CuWO 4 on the tribotechnical properties of antifriction material Cu-Sn-CuWO 4 -MoS 2 is analyzed at a pressure between 1.25 and 17.5 MPa and sliding speeds of 0.5 and 1.0 m/sec with liquid lubrication. It is established that the composite antifriction material Cu-Sn-CuWO 4 -MoS 2 can perform up to 17.5 MPa at a sliding speed of 0.5 m/sec and up to 12.5 MPa at 1 m/sec. The antifriction composite Cu-9 Sn-7.5 CuWO 4 -5 MoS 2 has the optimal friction coefficient (0.135-0.01) and wear (6.0-3.1 μm/km) between 1.25-12.5 MPa under the above conditions and can perform up to 150°C. When Cu-Sn-CuWO 4 -MoS 2 is sintered in hydrogen, CuWO 4 decomposes and reduces to pure metal, and tungsten particles reinforce the matrix. The antifriction material Cu-Sn-CuWO 4 -MoS 2 is microheterogeneous. The load-bearing component (matrix) represents an α-solid solution of tin in copper. Fine tungsten particles that are uniformly distributed in the matrix reinforce it and improve the bearing capacity of the material. Inclusions of molybdenum disulphide contribute to the formation of secondary structures on the friction surface and decrease the friction coefficient.

Structural and phase transformations in the tribosynthesis area of copper-based self-lubricating composite material

The paper examines the structural self-organization and adaptation of the surface layers of self-lubricating composite antifriction material (SCAM) IPM-304 to friction conditions. It is shown that temperature jumps and elastoplastic deformation are observed in the tribological contact area in SCAM performance in vacuum under friction. These factors and the difference in thermal expansion coefficients of the matrix and lead, for example, cause partial melting, isolation, layer-by-layer change in shape and size, plasticization, and rearrangement of the antifriction and reinforcing components in thin layers of the friction surface. This results in layer-by-layer changes in the chemical and phase composition, structure, and mechanical properties of surface layers. That is, tribosynthesis proceeds on the material layer responsible for the improvement of SCAM tribotechnical characteristics: decrease in friction coefficient and increase in wear resistance.

Structure and properties of composite sintered material of the type iron-cast iron

New antifriction alloys, synthesized from mixtures of iron and cast iron powders, have been developed. A special cast iron, with interdendritic point graphite inclusions, whose initial forms and sizes remain the same after sintering while being distributed among the grains, is used to create the composite materials. Starting at sintering temperatures of 800°C a pearlitic ferrite or pearlite structure forms with initial graphite inclusions that prevent formation of structure-free cementite. A composite antifriction material with a low friction coefficient can be obtained by optimizing the process parameters and charge composition as well as the microstructure of the alloys.