Technological support of friction unit at commissioning stage by forming the running-in coatings

Abstract

The dissertation is devoted to the solution of the actual scientific and technical problem in the field of branch mechanical engineering: development of innovative, energy efficient and environmentally friendly technology to improve the working condition of the friction surface to promote running-in conditions, deformation under high specific load provides automatic adjustment and compensation of bronze bearing shells for manufacturing errors. Solving this problem will increase the reliability of the rotary machines, increase the life of their working bodies, and reduce energy consumption, which is very important for modern Ukraine. Object of research - Technological process of formation of functional coatings on the surface of elements of machines with bronze bushes for sliding bearings of rotating mechanisms. Subject of research - The running-in coatings on the surface of tin bronze bushes that was formed by electro-spark deposition (ESD) applying the antifriction material of silver, copper, Babbitt B83 or graphene oxide (GO). The purpose of the study is ensuring the reliability and durability of the rotating mechanisms friction units by improving the tribosurfaces quality at commissioning stage the special running-in coating formation. To achieve this goal, it is necessary to solve the following tasks: 1. To analyze the manufacturing technology and features of the friction units operation; 2. To analyze structural and technological methods of increasing the reliability and durability of friction units; 3. Develop a system of directional selection of technological parameters for forming running-in coatings on various contact surfaces of friction units; 4. Establish correlation dependencies between equipment modes and quality parameters of the formed coatings; 5. To introduce the results of research into the practice of manufacturing friction units in the enterprise. In the introduction, the choice of the topic of the dissertation and scientific tasks is substantiated, the purpose and tasks of research are formulated, the scientific novelty and practical value of the received results are defined, and also the information on approbation, structure and volume of work is resulted. In the first chapter, the principle, equipment, detection method, treatment process and discharge mechanism of the electro-spark deposition technology will be comprehensively introduced. The effects of various process parameters on the mass transfer, surface roughness, elemental composition, microstructure and mechanical properties of the coating will be deeply studied. The effects of this treatment method on the phase composition, material hardness and friction and wear properties of the coatings will be systematically analyzed. All this allowed to formulate the purpose and tasks of the dissertation. In the second chapter, the basic principle of ESD technology is introduced in detail, the testing methods of surface roughness, surface morphology, element composition, phase composition, hardness and tribological properties are established, and the coatings performance index system is constructed, the principle of determining the weight by entropy method is derived, and the TOPSIS model is used for comprehensive evaluation. The experimental materials, experimental equipment and coatings preparation process involved in this paper are introduced. In the third chapter, the mechanism of low friction coefficient and the formation process of the coatings are described. The mass transfer, surface roughness, microstructure and elemental composition of the coatings are studied. The effects of process parameters on the thickness, phase composition, hardness and tribological properties of the coatings were studied. In the fourth chapter, the traditional processing and manufacturing process of plain bearing bush is briefly introduced, the test results of different running-in coatings are summarized and analyzed, the entropy method is used to determine the weight of running-in coatings index, and the TOPSIS model is used to comprehensively evaluate and sort the running-in coatings, and the best industrial application scheme is determined. The base material, coating material, processing technology and coating technology of bearing bush which affect the product quality are analyzed. A new environmental protection technology of constructing running-in coatings of tin bronze bearing bush is put forward, and the technical design, manufacture, processing, installation and trial operation are described in detail. Finally, some technical suggestions for the application of running-in coatings process of tin bronze bearing are put forward. In the fifth chapter, the full text is summarized, conclusions are drawn, and suggestions for future research are put forward. According to the set purpose and tasks in work the following results are received: 1. TheThe soft material coating of silver soft material coating of silver underunder the optimal process parameters, the the optimal process parameters, the mass transfer is 25.0mass transfer is 25.0 mg, the surface roughness of the Agmg, the surface roughness of the Ag coating is 15.46coating is 15.46 μmμm and the and the thickness is 15thickness is 15 μm. The minimum friction coefficient of the Ag coating is about 0.31. μm. The minimum friction coefficient of the Ag coating is about 0.31. However, the performance of silver as antifriction material coating needs to be further However, the performance of silver as antifriction material coating needs to be further improved.improved. 2. Under the optimal process parametersers of the soft material coatings of silver and of the soft material coatings of silver and Babbitt B83Babbitt B83, the mass transfer is 125.2, the mass transfer is 125.2 mg, the surface roughness of the mg, the surface roughness of the compositecomposite coatings is 19.43coatings is 19.43 μm and the maximuμm and the maximum thickness of the layers is 80m thickness of the layers is 80 μm.μm. The minimum The minimum friction coefficient of the composite coatingfriction coefficient of the composite coatings is about 0.177 after runnings is about 0.177 after running--in stage.in stage. The The main wear mechanism of composite coatings prepared under optimal process main wear mechanism of composite coatings prepared under optimal process parameters isparameters is plastic dplastic deformation and abrasive weareformation and abrasive wear. 3. Under the optimal process parametersUnder the optimal process parameters of the soft antifriction material of silver, of the soft antifriction material of silver, copper and Babbitt B83copper and Babbitt B83, the mass transfer is 54.4, the mass transfer is 54.4 mg/cmmg/cm22, the surface roughness of the , the surface roughness of the compositecomposite coatings is 32.3coatings is 32.3 μmμm. . The coatings are dense, metallurgical fusion with the The coatings are dense, metallurgical fusion with the substrate andsubstrate and under the optimal parameters, the thickness of the coatings is under the optimal parameters, the thickness of the coatings is about 100about 100 μm and the maximum thickness is 160μm and the maximum thickness is 160 μm. The hardness distribution from the coatingμm. The hardness distribution from the coatingss surface to the substrate increases first, then decreases and then increases gradually. The surface to the substrate increases first, then decreases and then increases gradually. The surface microhardness of the composite coatings is surface microhardness of the composite coatings is 2929 HVHV0.010.01, which is , which is about 82% lower about 82% lower than that of tin bronze substrate (161than that of tin bronze substrate (161 HVHV0.010.01).). The surface friction coefficient of the The surface friction coefficient of the composite coatings is 55.6% of the tin bronze substrate. The main wear mechanism of composite coatings is 55.6% of the tin bronze substrate. The main wear mechanism of composite coatingscomposite coatings is is plastic deformation accompanied by plastic deformation accompanied by slight polishing.slight polishing. 4. The runningThe running--in coatings on the tin bronze by electroin coatings on the tin bronze by electro--spark deposition (ESD) spark deposition (ESD) applying the antifriction material of silver, copper, Babbitt B83 and graphene oxide applying the antifriction material of silver, copper, Babbitt B83 and graphene oxide (GO). The results show that (GO). The results show that underunder the optimal process parameters, the massthe optimal process parameters, the mass transfer is transfer is 244.2244.2 mg, the surface roughness of is 15.9mg, the surface roughness of is 15.9 μm and the thickness of the layers is 160μm and the thickness of the layers is 160 μm. μm. The modulus and the hardness of the runningThe modulus and the hardness of the running--in coatings is 24.9% and 14.2% of the in coatings is 24.9% and 14.2% of the substrate, and the deformation ratio of the coatings is 10.2% higher thasubstrate, and the deformation ratio of the coatings is 10.2% higher than that of the n that of the substrate. The friction coefficient of the runningsubstrate. The friction coefficient of the running--in coatings is about 0.210 after in coatings is about 0.210 after runningrunning--in stage which is 64.8% of thein stage which is 64.8% of the substrate (0.324). The main wear mechanism of substrate (0.324). The main wear mechanism of the runningthe running--in coatings is plastic deformationin coatings is plastic deformation, scratching , scratching andand slight polslight polishing. ishing. The The runningrunning--in coatings deformation under action of high specific loads provides parts in coatings deformation under action of high specific loads provides parts automatic adjustment and compensation of manufacturing errors.automatic adjustment and compensation of manufacturing errors. 5. An evaluation indicator system for the characterization was constructed based on An evaluation indicator system for the characterization was constructed based on 6 6 factors including material price, time, mass transfer, roughness, thickness and friction factors including material price, time, mass transfer, roughness, thickness and friction coefficient of the coatings by electrocoefficient of the coatings by electro--spark deposition. An integrated coatings spark deposition. An integrated coatings characterization assessment approach is proposed here by combining a multicharacterization assessment approach is proposed here by combining a multi--criteriacriteria decdecision making technique, the technique for order preference by similarity to ideal ision making technique, the technique for order preference by similarity to ideal solution (TOPSIS), with the Shannon entropy method.solution (TOPSIS), with the Shannon entropy method. 6. Technical recommendations for the manufacture of rotary machinery involving Technical recommendations for the manufacture of rotary machinery involving tin bronze bushes for plain bearings have been formulated and implemented, with an tin bronze bushes for plain bearings have been formulated and implemented, with an expected economic benefit of expected economic benefit of 216 thousand UAH for environmentally friendly methods.for environmentally friendly methods. Scientific novelty of the obtained results: 1. For the first time, Tin bronze QSn10-1 is selected as the substrate material, and silver, copper, B83, GO are selected as the coating materials. The substrate and the coatings have a good metallurgical bonding, a new Ag3Sn phase is formed, the grain size is refined, the surface hardness is reduced, and the friction coefficient is greatly reduced. It is very suitable for running-in coatings. 2. For the first time, according to the selected substrate material and coatings materials, the process parameters of electro-spark deposition were studied, and the equipment DZ-4000III was selected as the deposition equipment to find out the optimal electro-spark deposition parameters. 3. For the first time, the index evaluation system of electro-spark deposition coatings was established, the weight of each index was determined by entropy method, and the TOPSIS model was used to comprehensively evaluate different coatings. The practical significance of the obtained results is to provide technical suggestions for the manufacture of tin bronze Bush of sliding bearing in rotating machinery. Adapt to that technical cycle of sliding bearing in rotating machinery and the operating conditions of friction unit using tin bronze bushes for the rotating running of the core components.