Influence of Wire Type on the Structure and Properties of Coatings Obtained by Electric Arc Metallization

Road transport ensures a rational organization of production and transportation of products. The cylinder block is a basic part, mechanisms and engine parts are attached to it. Engine blocks are operated with high loads. Defects arise and develop, which can be eliminated during major repairs. Improving the methods of restoring worn cylinder blocks of automobile engines is an urgent task. The possibility of restoring parts with such defects by gas-thermal methods was considered. The total level of defects that can be eliminated by applying a restorative coating by the method of electric arc metallization is 37%. The analysis of literary sources shows that surfacing and welding methods do not ensure the quality of the restored part. Gas-thermal methods are often used in the process of repairing parts. The most technological and effective is electric arc metallization. Productivity of electric arc metallization can be very high. Operating costs of using electrometallization are small. The equipment is relatively simple. Restoration of parts by electric arc metallization increases wear resistance and durability of the engine. To assess the repeatability of block defects, we analyzed a sample of 20 truck cylinder blocks from different manufacturers. It was established that the resource of the block depends on: wear of the main bearing beds, holes, cracks, damage to the thread and breakage of pins and holes. Laboratory experiments on the application of electroplating coating were carried out on samples of high-strength cast iron. Preparatory processing of samples - shot blasting. Experiments on sputtering of samples were carried out with known powder wires PG-SR4 and PG-SR4+3% Al with a diameter of 2.0 mm. Spraying was carried out with an EM-17 electric arc metallizer. Tests on the adhesion strength of the coating to the base metal were carried out using the adhesive method. From the research results, we can see that the coating applied with PG-SR4+3%A1 wire is destroyed at the joint under a higher load than the corrosion formed by PG-SR4 wire. At the same time, the adhesion strength also exceeds, and is 22.9 MPa. The microhardness of the coating built up with powder wire PG-SR4+3%A1 exceeds the level of microhardness of the surface built up with wire PG-SR4. Microhardness in both cases. decreases with distance from the surface of the deposited layer. Conclusions. From the conducted research, it follows that the electric arc restoration does not have a thermal effect on the part, provides high adhesion strength of the applied layer, which prevails over the majority of traditional methods of restoration of parts. In addition, the method of electric arc metallization is characterized by low energy consumption, small-sized and mobile technological equipment. Therefore, there is a need to continue the research of electric arc metallization in the restoration of worn surfaces of car parts.

The method of electric arc metallization has both undeniable advantages and some disadvantages. For example, there is a burnout of alloying elements and a high content of oxides in the applied coating. Aerosol fluxing during metallization can solve this problem and neutralize the negative oxidative effect of interaction of the applied metal with air oxygen. This article discusses an effective method to improve physical and mechanical properties of an electrometallization coating using aerosol fluxing. The essence of this method is introduction of an aerosol together with compressed air into a torch of molten metal. This aerosol consists of an aqueous solution of the chemical inorganic materials. Such the aqueous solution is poured into a hydrodispergator, which is connected to the air channel of the metallizer. Aerosol fluxing makes it possible to deoxidize and ligate metal during electric arc metallization. As a result, the physical and mechanical properties of the metal increase. The paper considers the results of topographic studies of electrometallization coatings. Formed coatings have a structure with grain sizes from 200 to 2500 nm and also have pronounced and subtle grain boundaries. Aerosol fluxing with electric arc metallization forms a coating with finer-grained structure, which increases their strength. It is established that formed coatings have a finer-grained structure and increased strength when using aerosol fluxing during electric arc metallization. Metallographic studies showed that the thickness of the electrometallization coating varies from 2490 µm to 2586 µm. The use of aerosol fluxing during electric arc metallization does not significantly affect the coating thickness. The microhardness of electrometallization coatings was studied. This study showed that the use of aerosol flux consisting of Na2CO3 , Na3AlF6 , Na2B4O7 during metallization increases microhardness of electrometallization coatings by 1.6 – 1.9 times.

The application of various types of functional and protective coatings made of inorganic materials to parts made of conventional structural materials will be able to solve the issue of ensuring the planned service life of modern devices, machines and mechanisms. Electric arc metallization, characterized by relatively high productivity and low cost of coating, serves as one of the methods of applying gas-thermal coatings. However, the high porosity of the resulting coatings, their low adhesion strength to the substrate and plastic properties prevent the widespread use of this method. (Research purpose) The research purpose is in studying the chemical, thermal and mechanical effects on samples obtained by electric arc metallization, on the adhesive, cohesive and strength properties of the coating and the areas of connection of the coating with the substrate. (Materials and methods) The authors used electric arc metallization and gas-dynamic spraying to obtain the necessary coatings. A mechanical effect on the coating was studied using the machine IZH- 250TV and special research equipment to determine the properties of coatings and substrates. (Results and discussion) Gas-thermal coatings can be successfully used in the manufacture of new and restoration of worn parts of agricultural machinery. The processing of metallized samples by surface plastic deformation are expedient and necessary. Chemical and thermal treatment has a positive effect on the properties of the coating and the substrate, increasing the value of microhardness by 50-70 percent. The use of supersonic metallization devices leads to an increase in adhesive strength by 30-35 percent. (Conclusions) The study showed that chemical and thermal treatment has a positive effect on the properties of the coating. Plastic deformation of the sprayed surfaces is practically equivalent to thermodynamic effect. It is recommended to use plastic deformation for spraying cylindrical surfaces.

The article considers the electric arc metallization technological modes of steel 30KhGSA wires, which affect thestructure formation and properties ofcoatings.Electric arc spraying was carried out using an SX-600 electric arc metallizer. The properties and characteristics of the resulting coatings depend on several plating parameters such as wire feed speed, voltage, and amperage. The coating structure was studied by electron microscopy and metallographic analysis. The coating has a layered structure, which consists of frozen convective metal flows, micro-welded small metal particles and oxides. The results of the study show that an increase in the wire feed speed during metallization leads to an increase in the resulting coating thickness per unit time. On the surface of steel 45, depending on the selected mode, coatings were formedfromsteel30KhGSAwithathicknessintherangefrom50μmto370μm.Ithasbeenestablishedthat when electric arc metallization coatings are sprayed with 30KhGSA wire, the microhardness of the surface layer increases by a factor of 2 relative to the microhardness of 45 steel. Based on studies investigating the impact of various factors in the electric arc spraying process on the formation of coating structures and properties, it can be deduced that utilizing electric arc metallization on steel 30KhGSA substrates allows for the production of coatings with enhanced hardness.

This study investigates the technological parameters of electric arc metallization applied to 30KHGSA steel, focusing on the effects of varying the spraying distance (100–250 mm) and gas pressure (6–9 Pa) on the resulting coating structure and properties. The spraying was performed using an SX-600 electric arc metallizer. Electron microscopy and metallographic analysis revealed that the coatings possess a layered structure consisting of solidified convective metal flows, micro-welded particles, and oxide inclusions. The optimal spraying parameters–150 mm distance and 7 Pa pressure–yielded the maximum coating thickness (729.58–733.62 μm) and the lowest porosity (4.02–4.33%). It was observed that increasing the spraying distance beyond 150 mm leads to reduced coating thickness, while deviations from the optimal gas pres sure result in decreased structural density and homogeneity. Electric arc metallization of 30KHGSA steel under optimal conditions enables the formation of coatings with enhanced wear resistance and mechani cal strength. Specifically, spraying distances over 150 mm and pressures outside the 7–8 Pa range nega tively affect the coating’s density, uniformity, and tribological performance. The identified optimal range (150–200 mm, 7–8 Pa) promotes the development of coatings with low surface roughness, reduced friction coefficient, and improved wear resistance. Key words: arc spraying, steel coatings, microstructure, Vickers hardness, porosity, thickness

Measurement of eroded dentine tubule patency and roughness following novel dab-on or brushing abrasion

Введение. Качественная защита стальных конструкций от коррозионных повреждений является необходимым условием для обеспечения эксплуатационной надежности и долговечности зданий и сооружений. Цинкование – один из наиболее эффективных способов антикоррозийной защиты стальных конструкций. Вместе с тем восстановление поврежденнного в процессе эксплуатации цинкового покрытия является трудоемким и дорогим, а оценка качества повторного цинкования требует дополнительных исследований. В работе представлен метод восстановления антикоррозийного цинкового покрытия методом электродуговой металлизации (ЭДМ) и проанализированы результаты испытаний коррозионной стойкости покрытия, выполненного ЭДМ-методом. Основной решаемой задачей является качественная оценка возможности применения метода ЭДМ в построечных условиях. Цель исследования. Оценка коррозионной стойкости цинкового покрытия, нанесенного методом электродуговой металлизации на поврежденные в результате термического воздействия при сварке участки заводского цинкового покрытия стальных конструкций. Материалы и методы. Образцы для исследования изготовлены из оцинкованного стального проката и сварены дуговой электросваркой встык. Восстановление поврежденного цинкового покрытия выполнено методом электродуговой металлизации. За основу прогнозирования долговечности покрытия принят метод экспериментального исследования по разработанной программе ускоренных коррозионных испытаний. Результаты. Исследован участок поврежденного в результате термического воздействия цинкового покрытия в зоне сварного шва, определены параметры повреждений. Предложен метод восстановления повреждённого при выполнении сварочных работ цинкового покрытия стальных образцов. Представлены результаты качественной оценки долговечности восстановленного цинкового покрытия. Выводы. По результатам лабораторных исследований получены данные, позволяющие рекомендовать ЭДМ-метод для восстановления поврежденных участков антикоррозийного цинкового покрытия стальных конструкций в построечных условиях. Introduction. High-quality protection of steel structures from corrosion damage is a prerequisite for ensuring the operational reliability and durability of buildings and structures. Galvanizing is one of the most effective ways of corrosion protection of steel structures. At the same time, damage to the zinc coating during operation and the need to restore it is a time-consuming and expensive process, and assessing the quality of re-galvanizing requires additional research. The paper presents a method for restoring an anticorrosive zinc coating by electric arc metallization (EDM) and tests of the corrosion resistance of the coating made by the EDM method. The main task is to qualitatively evaluate whether the EDM method can be applied in building structures. The aim of research is to evaluate the ability of the zinc coating, applied using electric arc metallisation, to withstand corrosion in areas of the factory zinc coating of steel structures that have been subjected to heat exposure during welding. Materials and methods. The samples for the study are made of galvanized rolled steel and butt-welded by electric arc welding. The restoration of the damaged zinc coating was performed by the method of electric arc metallization. The method of experimental research based on the developed programme of accelerated corrosion tests was adopted as the basis for predicting the durability of the coating. Research outcomes. After studying the area where the zinc coating in the weld area was damaged by heat exposure, damage parameters were established. A method for fixing steel samples damaged during welding that has lost zinc coating is suggested. The paper presents the findings from a qualitative evaluation of the restored zinc coating's durability. Conclusions. The results of laboratory tests provided evidence that EDM technique serves as a feasible method for the restoration of damaged anticorrosive zinc coating in steel structures on a building site.

During seasonal work, as practice shows, the paintwork is subject to damage, which leads to the appearance of corrosion foci on steel structures, the removal of which requires considerable labor. The applied paint coatings of agricultural machinery are short-lived, therefore, the development and implementation of new progressive methods of protecting parts of agricultural machinery from corrosion is important. (Research purpose) The research purpose is to extend the service life of agricultural machinery by creating an anticorrosive coating by supersonic electric arc metallization with subsequent application of paint and varnish coating. (Materials and methods) Abrasive blasting with corundum was performed for preliminary preparation of the surface of the parts before coating by electric arc metallization. A specialized installation for electric arc supersonic metallization «Dragon» was used for coating, zinc-aluminum wire Zn85/Al15 was used as the applied material. (Results and discussion) Selected equipment for the preparation of parts and assemblies and the application of anticorrosive coating by supersonic electric arc metallization. We have completed the layout of the site for coating. The modes of supersonic electric arc metallization were established. The modes of obtaining high-quality and durable coating of products were worked out on the basis of the Kaluga Region state enterprise «Kaluga Machine-Technological Station». (Conclusions) Anticorrosive treatment of products operating in aggressive environments is most effective when two coatings are applied sequentially: anti-corrosion layer by electric arc metallization and subsequent application of a layer of paint and varnish coating. The use of the technology of abrasive blasting and anticorrosive protection of housing and frame structures of agricultural machinery by the method of supersonic electric arc metallization allows extending the service life of these structures for 12 years.

The aim of this study was to evaluate the effects of different polishing systems on the surface roughness of different nanocomposite resins using various analysis methods. Three types of nanocomposite resins were investigated in this study: supra-nanohybrid (Estelite Asteria), nanohybrid (GrandioSo), and nanoceramic composite resins (Ceram-X Spheretec One). Forty-eight disc-shaped specimens (4 mm in diameter, 2 mm in thickness) were fabricated using a Teflon mold and divided into four groups according to the different polishing systems (n=12). All specimens were processed with one of the following methods: Mylar strip (control), one-step polishers (Opti1step), two-step polishers (Clearfil TwistDia), or multistep polishers (Sof-Lex XT Pop-on). The surface roughness (Ra, μm) was measured by contact profilometry (Mahr, Marsurf PS1) (n=10) and scanning electron microscopy (SEM) (Thermo Fisher Scientific, Phenom XL) at 400× magnification (n=2). The data were statistically analyzed using Kruskal-Wallis and Bonferroni correction tests (p<0.05). In addition, the surface morphology and elemental content were examined by SEM and energy dispersive x-ray spectroscopy (EDS) analyses. Under SEM evaluation, in terms of the polishing systems, there were no significant differences in the surface roughness for supra-nanohybrid composite resin (p>0.05). The multistep polishers created lower surface roughness than the one-step polishers for nanohybrid and nanoceramic composites. In terms of the composite resins, supra-nanohybrid composite exhibited lower surface roughness than nanohybrid composite for all polishing systems (p<0.05). The SEM observations confirmed the surface roughness measurements related to the surface morphology. One-step and two-step polishers created porosity on the surface of nanohybrid and nanoceramic composites. EDS analysis indicated the elemental composition of the particles in the porous zones was quite close to diamond abrasives and glass fillers.

The results of the research on electric arc metallization in the form of a technique and installation, which allow modeling various positions of the electrodes in the spray jet are presented. Direct measurements of the total pressure in the local zone between the ends of the electrodes used for arc metallization are made. The research allows obtaining coatings with refractory oxides, with a large number of alloying elements. These measures will increase their wear resistance. Thus, for 2.4 mm electrodes with a gas pressure at the spraying system inlet of the arc spraying pistol P inlet =0.5±0.05 MPa and the absence of a gap between the inner parts of the electrode ends in the center of the interelectrode gap, rarefaction is created. The rarefaction value reaches 0.044 MPa. With the gap increase, the degree of pressure drop decreases: when the gap varies from 0 to 1.0 mm, the pressure in the center between the electrode ends varies within 0.044...0.16 MPa. With a gap between the electrode ends of 2 mm or more, the pressure drop is negligible. The characteristic changes in the spray jet structure in the presence of electrodes are confirmed by the results of shadow photography. The results obtained allowed making adjustments to the process flow diagram of electric arc metallization, with the specification of the presence of the zone of air flow around the electrodes and pressure drop in the interelectrode gap. Optimum conditions for the arc functioning are achieved with such a ratio of the rates of feeding and melting of the electrodes, when the gap between the inner surfaces of the ends is within 0.5...1.0 mm. The proposed technology will allow restoring the working surfaces of parts of machines and mechanisms in mechanical engineering, agriculture, car building

The article views fundamentally different scientific approaches to the study and processes control for metallopolymer friction units tribocontacts and, separately, for metal ones. The article presents the developed criteria for the choice of fillers in the composite: for example, in antifriction interfaces, it is a mechanism that forms secondary structures (friction transfer films); in friction interfaces, it is the introduction of reinforcing elements into a polymer composite, that, as a result of friction, can penetrate into the metal counterbody and strengthen it. At the same time, the strength characteristics were evaluated by quantum chemical calculations and experimental confirmation by X-ray electron and Auger electron spectroscopy (AES) data. As for the wear resistance increase in metal-to–metal tribosystems by traditional methods – electric arc metallization, gas-flame coating, detonation-gas, plasma, etc., they do not properly ensure stable operations of tribosystems. Currently, the most promising techniques used for surface modification and hardening are vacuum ion-plasma technologies. The ideas of applying thin-film coatings are based on techniques based on both physical processes (physical vapor deposition with PVD coating) and chemical principles (chemical deposition from the gas phase – CVD process). The PVD- method involves the transfer of the coating material to a vaporous state, followed by its delivery to the sample and vapor deposition on it. When using CVD methods, the coating on the sample is transferred from carbonites, organometallics, etc. The paper presents the results of research for finding the dependence of the physico-mechanical and tribological properties of coatings –PVD, DLC, high-entropy or combined, on the technological parameters of application.

A solution of two problems is proposed. The first task was technological, in which one of the ways of repairing and restoring the involved part was considered – the restoration of the eccentric sleeve of the GP 500 cone crusher for fine and fine crushing of ores by electric arc metallization. The second task is mathematical. A computational and theoretical analysis of the choice of optimal EDM modes for obtaining a high-quality coating with antifriction properties on the surface of an eccentric sleeve is carried out.Conclusion on research work: - a decrease in the purge flow rate leads to an increase in the influence of the aerodynamic drag coefficient of the air on the movement of the parts of the molten particle, i.e. the time during which the molten metal is collected into the spherical part of the particle increases, therefore the diameter of the sprayed particles increases; - materials selected from copper and steel wire make it possible to obtain a coating of the surface of the sprayed part with high antifriction properties, which increases the strength and service life of the eccentric sleeve restored in the operation of the cone crusher; - in this paper, an alloy consisting of two metals is presented and studied, but today there are a huge number of possibilities in choosing various modern coatings used for parts operating under conditions of intense abrasive wear, significant shock loads, pressure, rolling, friction, sliding of metal surfaces. As an innovation in electroplating technology, it is proposed to continue research on a larger scale with further determination of stronger alloys.

Preparation of anti-wax coatings and their anti-wax property in crude oil

Currently, the technology of arc metallization according to technical and economic indicators is a promising way to restore worn parts of equipment. In the coating process the cored wire is melted by an electric arc, and molten particles are accelerated towards the surface parts with high temperature gas flow. On the subsequent formation of strengthening coatings are significantly influenced the technological modes of electric arc metallization. As practice shows, the coatings obtained by electric arc metallization are characterized by a heterogeneous layered structure. The structure of powder coatings, the distribution, composition and properties of the phases affect on the wear resistance, hardness and strength of the machined surface of machine parts and mechanisms. It is therefore necessary a detailed study of the structure of wear-resistant coatings taking into account technological properties of cored wire, and process heating of the particles by arc spraying. In this work the X-ray microanalysis of the elements of the structure of wear-resistant coatings obtained from cored wire with a refractory additives were conducted. The results of the study will be useful for the improvement technology of electric-arc metallization cored wires.

The aims of this study were to evaluate the surface morphology and surface roughness of restorative materials containing glass ionomer, analyze Streptococcus mutans biofilm formation on the surface of materials, and determine the correlation between surface roughness and biofilm. Four restorative materials: resin-modified glass ionomer; giomer; amalgomer; and glass carbomer were used and for each material, 6 mm in diameter and 2 mm in thickness disc-shaped specimens were prepared to evaluate the surface morphology (n = 3), surface roughness (n = 16), and biofilm (n = 20). Surface morphology was analyzed with a scanning electron microscope. Surface roughness was evaluated via an atomic force microscope. The biofilm was evaluated by counting the colony-forming units. Surface roughness measurements were evaluated using a one-way analysis of variance and Tukey HSD test. Biofilm parameters were analyzed using the Kruskal-Wallis H and Mann-Whitney U test. Pearson's correlation test was used to determine the correlation between surface roughness and biofilm. While the highest roughness values were obtained for amalgomer and glass carbomer, the lowest roughness values belonged to giomer and resin-modified glass ionomer. Statistically significant differences in the number of adherent bacteria were observed between the materials only on day 1. No statistically significant correlation was determined between surface roughness and biofilm. The resin content and small filler particle size of material positively affect surface roughness. However, there is no direct relationship between surface roughness and biofilm.