Приведены результаты исследований усталостной прочности конструкционных материалов стали Ст45 и высокопрочного чугуна ВЧ60-2 с плазменными покрытиями относительно большой толщины из порошковой композиции, представляющей собой жаропрочный сплав ЭП-109 (ХН56ВМКЮ) на никелевой основе и алюминиево-магниевый порошок Al–Mg. На основании проведенных экспериментальных исследований получены математические модели, описывающие закономерности влияния технологических режимов плазменного напыления на усталостную прочность исследуемых конструкционных материалов. The results of studies of the fatigue strength of structural materials of steel St45 and high-strength cast iron HF60-2 with plasma coatings of relatively large thickness from a powder composition consisting of a heat-resistant alloy EP-109 (KHN56VMKYU) on a nickel base and aluminum-magnesium powder Al–Mg are presented. Based on the conducted experimental studies, mathematical models describing the patterns of influence of technological modes of plasma spraying on the fatigue strength of the studied structural materials have been obtained.

—The efficiency of application of a new technology for repairing hydraulic distributors with the restoration and strengthening of the worn surfaces of the life-determining joints of parts and increasing their wear resistance is evaluated. The hydraulic distributors repaired according to the proposed technology exhibit an increase in the average overhaul life under real operation by 1.24 times compared to the life in the pre-repair period of operation.

This paper provides the results of fatigue strength tests of structural materials including grade St45 steel and VCKh60-2 high-strength cast iron with plasma coatings. These coatings have a relatively large thickness and consist of the powder composition of EP-109 (KhN56VMKYu) heat-resistant nickel alloy and Al–Mg powder. Experiments have allowed deriving mathematical models to describe the patterns of the influence of the plasma spraying process modes on the fatigue strength of the tested structural materials.

This work is devoted to evaluation of the efficiency of a new technology for repairing gear pumps with the restoration of worn surfaces of resource-defining mates of parts and increasing their wear resistance. Hydraulic pumps repaired by the proposed technology showed an increase in the average overhaul life in conditions of real operation of 1.07 times as compared with the resource in the prerepair operation period.

The statistical relationship between the porosity of plasma-sprayed metal coatings and the distance and angle of spraying, the granulometric composition of the powder, and the current strength of the technological process is presented. Mathematical design of experiment is used. An adequate regression equation, which makes it possible to control the porosity of the metal coating by changing the plasma spraying factors, has been experimentally obtained. The steepest ascent method is used to determine the following rational coating deposition conditions, under which the porosity of the metal coating is 15

Data on the estimation and selection of working gases for powder plasma build-up welding are reported. Being selected appropriately, these gases protect molten metal against oxidation and stabilize arcing. The industrial use of plasma methods with a properly selected gas medium makes it possible to cover machine parts and equipment components by wear-resistant coatings. Mobile equipment for plasma build-up welding based on a KamAZ motor truck has been designed, as applied to which the thermophysical behavior of hot hydrocarbons has been considered. Recommendations for its use and operation control are given.

Статья посвящена оценке эффективности новой технологии ремонта шестеренных насосов с восстановлением изношенных поверхностей ресурсоопределяющих сопряжений деталей и повышением их износостойкости. Отремонтированные по предложенной технологии гидронасосы показали увеличение среднего межремонтного ресурса в условиях реальной эксплуатации в 1.07 раза по сравнению с ресурсом в доремонтный период эксплуатации.

Introduction. The bakery industry is an agricultural industry of high-level processing of raw materials focuses on the end-consumer. In the production of bakery products one of the operations of the technological process is performed by dough dividers of vacuumpiston type, whose service life is 30‒40% lower than the normative. The most promising method for restoration of worn parts of the suction mechanism is electrospark processing. When selecting the electrode material, it is important that they have not only low erosion resistance, but also high tribotechnical properties. Aim of the Article. The article deals with problem of selecting electric coatings to reduce wear of working surfaces of suction mechanism parts during repair of vacuum piston-type dough dividers. Materials and Methods. The analysis of the properties of electropark coatings was carried out by nondestructive testing methods using modern research equipment; the results were processed using the Compass-3D program. Results. There are determined the values of physical, mechanical, frictional and tribotechnical properties of electrospark coatings made of BrOS10-10 bronze and Kh15N60 alloy. The total wear rate for BrOS10-10 bronze coating was 8,3 ∙ 10‒12, and for Kh15N60 alloy 15 ∙ 10‒12. Discussion and Conclusion. Total wear rate on the friction machine of bronze coated samples is lower than that of basic friction pair in 1.4 times, and of alloy coated samples ‒ higher in 1.26 times. Adding of MODENGY solid-lubricant coating to the coating from the alloy reduces its abrasion ability by 3 times, and the total wear rate ‒ by 1.34 times in comparison with the base friction pair. The used calculation-experimental method showed low wear rate of electrospark coatings of bronze and alloy in relation to the material of parts of the suction mechanism of vacuum-piston-type dough dividing machines.

The results of a comprehensive assessment of the quality of coatings obtained by electrospark deposition technique are presented. The assessment was performed using modern measurement instruments and dedicated software packages to determine the parameters of micro- and macro-geometry of the coated surfaces. It has been established that the main criteria for assessing the thickness of electrospark coatings, used to restore and harden parts, are the minimum depth, as well as the maximum height and peak-to-valley distance of the profile. It has been proven that the optimal ratio between the length of the bearing friction surface that receives an external load and the length of the surface covered by lubricant is at least 80 % for tribotechnical friction couples, and at least 60 % for parts with hardened surface.

The dimensional barrier to increasing the thickness of electrospark coatings with increased contact continuity is addressed. The limitation on coating thickness is analyzed, and existing remedies are reviewed. Conditions in which thick coatings with no less than 80% contact continuity may be produced are identified, in the case of a BrKMts3-1 bronze electrode and samples of gray cast iron.

The influence of nanostructuring on the physicomechanical properties of electrospark coatings is assessed. The influence of structural transformations in coatings formed by electrospark treatment on their tribological properties is studied experimentally.

In electrical discharge machining, the formation of the modified surface layer depends on the physicochemical properties of the anode and cathode and the machining conditions. Experiments show that the mass transfer and coating thickness decrease with increase in thermal conductivity and decrease in melting point of the anode and cathode. The mass transfer and state of the modified surface are also impaired by increase in energy of the generator pulses and increase in roughness of the machined surface. These data are fundamental in selecting electrode materials and creating metal coatings with specified functional properties.

Introduction. To keep automobiles and tractors in operation conditions, it is necessary to restore the inner cylindrical surfaces of the friction pair parts. This is the most laborintensive activity. The method of electroplated contact deposition of composite coatings, based on elastic plastic deformation of formed layers, is used for repairing surfaces. To use this method it is necessary to determine the values of the elasticity modulus, on which the wear resistance of tribocouplings depends. Materials and Methods. For the study, cylindrical samples made of 30 HGSA and 30 HGSNA steels were used. Electrolyte containing 200–250 g/l chromium oxide, 2.0–2.5 g/l sulfuric acid, and distilled water was used for electroplating the coatings. When calculating the stress-strain state, the apparatus of continuum mechanics was used. Results. The dependence of the coating pliability as a function of the parameters of individual elementary layers is determined. When the multilayer coating of three types (orthogonal-reinforced, cross-reinforced and quasi-isotropic) is applied, its structure does not depend on the angles of kinematic tool movement on the inner cylindrical surface of the part. For each type of coatings, the way to determine the constant stiffness coefficients of the layers is specified. The dependences for calculating the elasticity modulus of the applied material are derived from the values of the stiffness coefficients. Discussion and Conclusion. In determining the modulus of elasticity of multilayered composite coatings, the calculation is made for the individual layers by passing to the convective coordinates, which is in complete agreement with the Lagrange point of view on the study of the motion of a continuous medium. The results obtained are of practical significance in the selection of the coating material to be applied for the restoration of internal cylindrical surfaces.

The influence of the machining conditions and the machining fluid on the burnishing of holes is considered. Applying Epilam coatings to the tool prevents loss of the machining fluid from the machining zone, with decrease in load and strain by half; the heat transfer in the machining zone also decreases, lowering the temperature by as much as 40°C. In hole burnishing, Epilam coatings more than triple the tool’s wear resistance.

The coating thickness produced by electrospark hardening depends on the erosion resistance of the electrode (anode). Dimensional analysis is used to derive a model taking account of the influence of the parameters of electrospark hardening, the size and characteristics of the electrode, the surface microgeometry of the anode in the contact zone, and the load on the electrode. The model permits the planning of experiments to better understand the influence of individual factors on the erosion of the anode.

Introduction. In the technical service enterprises, the reliable estimation of a technical condition of hydraulic gear pumps of tractor mounted hydraulic systems is a priority in introducing new repair processes. The absence of data of manufacturing plants on limiting wear of working surfaces of hydraulic pump details, when the decision on repair is taken, leads to the necessity of carrying out additional researches. In this regard, the purpose of work is to find the limit wear values for working surfaces of details of round gear hydraulic pumps. Materials and Methods. The laboratory tests of used round gear hydraulic pumps were carried out according to the method developed in the GOSNITI on the hydraulic bench of the KI-28097M-GOSNITI. The controlled parameter during tests is the pump delivery rate. Results. The results of laboratory bench and micrometer studies of used round gear hydraulic pumps are presented in the work. The mathematical model of pump delivery rate dependence on statistically significant independent factors is obtained. The limit values for wear of working surfaces of round gear hydraulic pump details are determined by the steepest ascent method on the received mathematical model. Discussion and Conclusion. According to the results of the input bench control of the used round gear pumps, 81% of the tested units were operated in the over-extreme limit state. The limit values for wear of working surfaces of round gear hydraulic pump details obtained by the steepest ascent method make it possible to make a conclusion about the necessity of their restoration in repairing at technical service enterprises.

Production costs and product quality in manufacturing depend directly on tool life in cold and hot machining of metals and alloys. The types of surface failure in tools are considered in the present work. The potential for increasing their wear resistance by electrospark coating deposition is noted. The dependence of the relative coating thickness on the relative limiting carrying capacity of the coating is determined for surface hardening of forged tools. The influence of the electrode composition on the resulting surface properties is analyzed.

The roughness is the most important characteristic of the working surfaces in machining parts. In the present work, the parameters of surface profiles formed by electric discharge machining (EDM) are statistically analyzed. On that basis, the influence of the margin selected in machining on the extent of the supporting surface is established. The results permit the determination of the relation between the length of the supporting frictional surface subject to external load and the length of the surface under the lubricant. That may be used in the creation of wear-resistant frictional pairs with high carrying capacity.

Introduction. Nowadays, vacuum-type dough dividers are used in industries with a production volume of up to 4,000 loaves per day. In the dough divider operation, due to wear of the working surfaces of the piston, chamber, and drum, the gap between them goes beyond the value equal to 50 microns, which provides vacuum in the suction chamber. As a result, the suction process becomes unstable; the dough divider disturbs the weight accuracy of bakery goods. Repair of such equipment is carried out mainly through a full or partial replacement of worn parts and assemblies with new ones. To increase their durability, there is a need to develop a new highly efficient technology with the restoration of worn part surfaces using the welding and surfacing methods.Materials and Methods. A new technique of determining the number of objects for research using the “STATISTICA” program is presented. Wear surfaces of the vacuum dough divider parts are determined.Research Results. Micrometric studies of the dough divider components were carried out. They showed the presence of appreciable size distortions due to the local wear of the working surfaces. In this case, a side gap between the suction chamber and the main piston and between the drum and the suction chamber is 6 times higher than the permissible one, and a vertical gap between the division box and the piston exceeds the permissible gap by more than 10 times. Wear of the working surfaces of the dough divider parts is local in nature, while the range of values is as follows: for the main piston, it is 10-200 microns; for the gaging piston, it is 250- 900 microns; for the suction chamber and division box, it is 300-400 microns; for the drum surfaces, it is 280-300 microns.Discussion and Conclusions.The conducted micrometric studies showed the presence of appreciable size distortions due to the local wear of the working surfaces. Based on the results obtained, it can be argued that the most productive and economically viable technique for the restoration of worn surfaces of dough divider parts is, for example, the electrospark machining.