Development of Porous Films Based on Polyanionic Cellulose to Form Functional Coatings

New porous films based on polyanionic cellulose with AlOOH nanoparticles have been developed. The morphology of the films has been studied by electron microscopy: the size of the formed pores is 1000-500 microns; the total surface porosity of the films is 30%. Using infrared microscopy, it was shown that during the formation of porous films, their chemical composition remains unchanged. Differential scanning calorimetry was used to determine the threshold for thermal destruction of porous films: 306 С. The possibility of using the obtained materials as antifriction coatings when filling the pores with solid lubricant MoS2 is considered. It is shown that for a steel sample protected by a porous coating with MoS2, the friction coefficient decreases by 50% compared to the friction coefficient for a steel surface under a load of up to 450 MPa.

Comparison of the modifying effect of rice ashand buckwheat husk in epoxy antifriction coatings

This paper discusses the issue of utilization of rice and buckwheat husks, a comparison of their modifying effect in epoxy antifriction coatings, for this, the elemental composition of these fillers was determined using X-ray fluorescence analysis, their structure was analyzed by scanning electron microscopy, and the acid-base characteristics of the filler surface were determined by the pH method., the surface area of the pores of the ash of rice and buckwheat husks, their oil absorption were calculated, a sol-gel analysis was carried out to assess the density of the spatial network of filled epoxy coatings, and their wear resistance and hardness were determined. In the course of the research, the optimal temperature for obtaining ash from rice and buckwheat husks was established, which contributes to an increase in wear resistance, hardness and a decrease in the static friction coefficient of filled epoxy coatings. It is shown that the optimal temperature for obtaining rice husk ash is 500 C, and buckwheat husk ash 800 C. At the same time, rice husk ash is a more effective filler for epoxy polymers than buckwheat husk ash, since it increases the hardness of materials and provides a greater decrease in their friction coefficient.

Technological factors influence on the antifriction coatings quality

The conditions for the antifriction coatings formation during finishing antifriction non-abrasive treatment (FANT) are analyzed. The requirements for this kind of coatings and the main criteria for assessing their quality are noted. A relationship has been established between the quality of the coating obtained with FANT and the technological factors that determine the conditions for contacting the tool with the treated surface. It is proved that the shape and size of microroughnesses of the treated surface determine the efficiency of the microcutting process and filling the microcavities with the rubbed material. Technological factors influence on the coating quality was investigated during FANT by implementing a multifactor experiment, as a result of which a connection was established between the technological parameters of the process (total friction path, load on the tool), as well as the length of the supporting surface with indicators characterizing the coating quality. Statistical models were obtained for mass transfer of antifriction material, area (continuity) of the coating and surface roughness at natural values of the factors, which made it possible to establish the studied factors influence on the optimization parameters. The analysis of the experimental scattering graphs made it possible to clarify the nature of the factors changes and analyze their mutual influence on the optimization criteria. Taking into account the inversely proportional relationship of the optimization criteria, the achievement of their maximum values at the same time is impossible, therefore, the values are taken according to the final result of the FANT process. The range of the studied factors values is established, the regularities of their change are substantiated from the point of view of the selected optimization criteria. Determination the rational values of the FANT process technological parameters will improve the antifriction coatings quality obtained by a friction-mechanical method.

OPTIMIZATION OF THE PROCESS OF MULTILAYER CENTRIFUGAL INDUCTION SURFACING OF COATINGS BASED ON ALUMINUM ALLOYS

As a result of the conducted research, using the methods of mathematical planning of the experiment, the optimization of the process of multilayer centrifugal induction surfacing of antifriction coatings based on aluminum alloys was performed, which made it possible to develop a mathematical model and determine the optimal range of values of technological modes. The dependences of the minimum wear rate of the coating material Iq (mg/m) on the parameters of multilayer induction centrifugal surfacing of aluminum alloy coatings are established. The main factors affecting the wear rate of the coating were the heating temperature of the part T (°C), the time of the isothermal exposure t (min) and the speed of rotation of the part n (rpm). Based on the results of computational and experimental modeling, it is shown that in order to obtain the optimal wear intensity of the aluminum alloy coating material, the parameters of the multilayer centrifugal induction surfacing process should be as follows: the rotation speed of the part n = 1,750–1,875 rpm, the heating temperature of the part T = 775–800 °C, the isothermal exposure time t = 7–8 min.

Formation of MAO-coatings of high thickness on titanium alloys and evaluation of tribological properties in friction pair with bronze

The article presents experimental data on the effect of microarc oxidation parameters on the thickness and structure of the MAO-coating and its tribological characteristics in friction against bronze. The appli- cation of thick antifriction coatings by the MAO-method on titanium alloys has been developed. The possibility of using MAO-coatings of high thickness in sliding friction units was investigated.

SYNTHESIS OF ANTIFRICTION COATINGS BY THE FABO METHOD

In the paper, the technology of obtaining antifriction coatings by the method of finishing antifriction-free abrasive treatment with the implementation of the wear-free effect is proposed. (Research purpose) The research purpose is in developing an effective technology for obtaining copper coatings on the surface of steel parts of the shaft type to reduce the wear rate in the conditions of oil starvation of machine parts. (Materials and methods) During the study, a laboratory facility for the synthesis of antifriction coatings on the surface of steel parts by the method of finishing antifriction-free abrasive treatment has been developed. Brass of the LS-59-1 brand was used as a material for applying a copper antifriction coating. In order to activate the surface of the part and the surface of the filler material, a technological medium based on a ten percent solution of hydrochloric acid and glycerol was used. Authors determined the composition of the technological environment empirically. The obtained laboratory samples were subjected to tribological studies in comparison with standard antifriction alloys. X-ray diffraction studies were performed to determine the phase composition. (Results and discussion) As a result of X-ray diffraction studies of laboratory samples, the presence of iron and copper components in the synthesized coating was studied. The content of oxides on the surface of the coating is insignificant, the internal structure is dense with no visible porosity. The coating consists of 95 percent copper, the synthesis process takes place without oxidation, which gives the coating a high adhesive and cohesive strength. The coating thickness is uniform and varies within 3-5 micrometers. (Conclusions) Comparative tribological studies have shown high resistance to wear and to the setting of the contact surfaces under conditions of oil starvation. The coefficient of friction is stable and low and is in the range of 0.08-0.15. The developed technology makes it possible to increase the wear resistance of steel parts of the shaft type in the shortest possible time and with minimal material costs and can be successfully implemented in the conditions of repair enterprises.

INFLUENCE OF TECHNOLOGICAL FACTORSFOR THE QUALITY

The article contains a study of the influence of technological factors on the formation of a film antifriction coating when applied to parts of cars and cars. The article presents a methodology and results of calculating the adhesion strength of a film coating with a steel base. The equipment used to determine the adhesion strength is presented. The technique of using the specified equipment is described. The dependence of the adhesion strength on the modes of film coating is established and described. Recommendations have been developed for the selection and method of applying film antifriction coatings during the maintenance and repair of motor vehicles.

EPOXY ANTIFRICTION COATINGS FILLED WITH THE RICE HUSKS ASH TREATED WITH SURFACTANTS

The use of epoxy antifriction coatings can significantly reduce thermal stress in the friction zone and expand the coating working temperature interval while keeping high wear resistance. The paper considers the effect of non-activated and activated by surfactants silicate filler – rice husk ash on the physicochemical and mechanical properties of epoxy materials applied as antifriction coatings. All studied samples of rice husk ash, both initial and activated with surfactants, have an alkaline surface nature. The study identified that all cationic quaternary ammonium salts (QAS) reduce the pH of rice husk ash. At the same time, nonionic OXIPAV increases this indicator. Activation of the rice husk ash surface, both by the quaternary ammonium salts and aminosilanes, significantly reduces the porosity of this silicate. In this case, the average pore diameter does not change significantly, and their specific surface area decreases significantly, to a lesser extent, when activated by nonionic quaternary ammonium salts. The application of quaternary ammonium salts and aminosilanes in the amount of 33 % for activation of the surface of the investigated silicate filler reduces its modifying effect in epoxy compositions, regardless of the chemical structure of the surfactants used, which is not a typical effect. Therefore, the authors assumed that the suboptimal concentration of quaternary ammonium salts and aminosilanes was used. The study identified that the optimal concentration of 50 % alcohol solution of KATAPAV is 14.7–21 %. In this range of the QAS content, there is a significant increase in hardness (about 40 %), a slight decrease in wear (about 10 %), and a significant decrease in the coefficient of static friction (up to 2 times). At the same time, the authors observed an increase in adhesion to metal up to 3 times and bending strength up to 25 %. Thus, rice husk ash activated with an optimal amount of quaternary ammonium salts is an effective modifier of epoxy coatings, which improves their antifriction properties and increases wear resistance, hardness, strength, and adhesion characteristics.

Methods for the construction of lowered structures and pile foundations

The paper discusses the methods of erecting sunk wells and pile foundations, which consist in regulating the frictional forces of soils: lowering along the lateral surface when sinking wells and increasing when erecting pile foundations. The developed method of sinking wells provides for the application of two types of effective antifriction coatings along the lateral surface: along the cutting edge of the structure and above the cutting ledge. At the same time, the coefficients of reducing the friction forces by these coatings for various types of soils have been established, and a method for calculating sunk wells for lowering is proposed, taking into account the use of the developed submerging method. To increase the friction forces on the lateral surface of the driven piles and to increase their bearing capacity, modular piles with a developed lateral surface of the T-section have been developed and introduced. The areas of rational use of these piles are established depending on the types of soils (clay and sandy) and the depth of their penetration.

POLYMER MATERIALS FOR ANTIFRICTION COATINGS (review)

An overview of polymeric materials of various structures used as antifriction materials is given. The experience of using various polymeric materials for the manufacture of antifriction coatings is considered. The advantages of thermosetting and thermoplastic polymers in comparison with metallic materials are revealed. Some compositions of carbon and organoplastics developed for plain bearings are described. A conclusion is made about the direction of research in the development of new binders for antifriction materials.