Electric Arc Spraying Research Articles

Determination of abrasion resistance of Fe28Cr5C1Mn coating applied to 30MnB5 boron alloy cultivator blades via electric arc spray

The poor abrasive wear behavior of agricultural machinery affects the farmers all over the world, rendering their activities more inefficient and negatively affecting their productivity. Therefore, innovation in the manufacture of soil cultivation machinery and the selection of wear-resistant materials has been of great importance. Recently, boron alloys, in particular, have been used in the manufacture of machinery parts that work the soil. The aim of this was to investigate the behavior of the blades of the machines widely used in soil cultivation in agricultural production following a surface treatment technique. For this purpose, the blades made of 30MnB5, a material widely used in the production of cultivator blades, were used as substrate samples in the trials as well as blades of the same substrate coated with Fe28Cr5C1Mn alloy wire via the electric arc spray technique. The morphologies and structures of the uncoated and coated samples were comprehensively analyzed by light microscopy, scanning electron microscopy, energy dispersive spectrometry and X-ray diffraction. In addition, their microhardness, porosity, and surface roughness properties were assessed separately before and after plowing. These prepared blades were tested under in the same conditions by plowing the same field at two different soil moisture. Although the weight loss was measured as 9.4 g and 5.4 g in the uncoated and in the coated sample at 9% moisture level, respectively, the weight losses were at 14% humidity level were 10.6 g and 5.9 g in the uncoated and coated samples, respectively. Although the amount of wear increased with increasing humidity levels in both groups, the mass wear loss in cultivator blades coated with Fe25Cr5C1Mn alloy wire was found to be lower in all trials. The results suggest that coating the cultivator blades using electric arc spray would increase agricultural productivity and reduce factors that cause environmental pollution.

Development of Zinc and Low Carbon Steel Coatings on ABS Plastic by Electric ARC Spraying

<div class="section abstract"><div class="htmlview paragraph">Acrylonitrile Butadiene Styrene (ABS) is a highly sought-after engineering plastic for industrial applications, particularly in modern aircrafts. It offers better balance of impact strength, tensile strength, thermal resistance, dimensional stability, processing ability and affordability, the aircraft interior parts are made up of ABS plastic. However, ABS plastic is not a good choice for heavy-duty industrial applications that require corrosion resistance, abrasion resistance and durability. Several studies have been published on surface metallization of ABS plastic using conventional electroplating and electroless methods, but there is little information is available on the use of thermal spray technique. This opens up a huge opportunity for research in this area to be conducted using most commonly used materials like zinc and low carbon steel. In the light of the above, the current work employs an electric arc spray technique to coat zinc and low carbon steel on ABS plastic. Prior to coating the alumina grit blasting was carried on tensile and bending samples which were prepared as per ASTM D638 and ASTM D790 standards respectively. Comparative studies showed that the zinc coated ABS samples showed better tensile strength, flexural strength and flexural modulus than that of low carbon steel coated ABS specimen. Visual examination showed good surface finish with no surface damage for zinc coated ABS component.</div></div>

IMPROVING THE PERFORMANCE PROPERTIES OF AUTOMOTIVE PARTS BY FORMING WEAR-RESISTANT COATINGS

The work is devoted to solving the scientific and technical problem of ensuring the tribotechnical properties of car parts through the use of wearresistant coatings. The synthesis of the main types of wear of car parts and ways to improve their tribotechnical properties was carried out, which allowed to substantiate the feasibility of using wear-resistant coatings to restore and strengthen them.An urgent problem is the reasonable search and development of highly efficient, easy-to-use technologies for the restoration of parts to improve the performance of cars. Solving this problem requires the introduction into practice of strengthening and restoring car parts wear-resistant coatings. Summarizing the results of research on the main types of wear of car parts allowed us to conclude that they work in conditions where operating loads (pressure, temperature, environmental action, etc.) perceive mainly their surface layers, and therefore it is enough to restore not all parts but only worn surfaces by applying wear-resistant coatings.It has been proven that to improve the performance of car parts, it is important to choose the right simple and affordable ways to apply coatings that will increase their service life. It is substantiated that among the methods of applying wear-resistant coatings are the most common, cheapest and simplest methods of gas-thermal spraying, namely gas-flame spraying and electric arc spraying. Restoration and strengthening of car parts by applying wear-resistant coatings has solved the problem of providing their resource, which is not inferior to the resource of new parts.

Зносостійкі покриття на алюмінієвих сплавах

Aluminum alloys are widely used in industry. Recently, they are used as a replacement for steel for the manufacture of pulleys, gears, columns of hydraulic rotary transmissions of grabs, etc. This reduces the weight of the parts and reduces carbon emissions into the atmosphere. However, aluminum alloys have low abrasive wear resistance, so their use is possible with coatings on the surface. High-speed gas flame spraying (HVOF) was carried out on the equipment (Diamond Jet Hybrid gun). Arc coatings with a thickness of 500 µm were applied using FMI metallizer and FMI-2 powder wire (Cr6Al6B3Fe-base). PEO (oxido ceramic) coatings were synthesized on D16T aluminum alloy in an electrolyte of 3 g/l KOH + 2 g/l liquid glass (sodium silicate) with a pulsed current at a frequency of 50 Hz, with the ratio of the densities of the cathode and anode currents Jc/Ja+15/15 A /dm2. The duration of the PEO process is 60 min. The open porosity of the coatings was determined by the method of hydrostatic weighing. The phase composition of the surface layers was studied using a DRON-3.0 diffractometer. HVOF (VC) and PEO coatings have been found to have 3 to 4 times higher wear resistance than high carbon hardened steel 100Cr6 and 2 times higher than galvanic chromium coatings, but have high energy consumption. Two methods have the lowest energy consumption: electric arc spraying of coatings and hard anodizing. At the same time, the wear resistance of such coatings is significantly lower than that of coatings obtained by the PEO and HVOF (VC) methods. For the restoration of worn parts, the most appropriate methods are HVOF (VC) and electric arc spraying, as they allow applying thick coatings up to 5 mm. Conclusions: It was established that the studied HVOF (VC), PEO, EDP and hard anodized coatings significantly increase the abrasive wear resistance of aluminum alloy parts. HVOF (VC) and electric arc spraying methods can be used to protect new and worn parts from wear. PEO and hard anodizing methods can be used to protect against wear on new parts only. The use of these methods increases the wear resistance of parts made of aluminum alloys to the level of steel and allows replacing steel and cast iron with aluminum alloys with coatings, reducing the weight of parts and carbon emissions into the atmosphere.

Assessment of physical-mechanical and protective-decorative properties of zinc coatings obtained by electric arc spraying

Described are effective methods of protecting metals from corrosion and the expediency of electric arc spraying for large-sized items outside production facilities. The hardness and strength of zinc coatings have been studied, the optimum thickness of coatings with high adhesion strength has been determined. A link has been established between laboratory studies of the adhesive strength of zinc coatings and the practical results of their application to protect the elements of transport systems. The protective and decorative properties of coatings were investigated by evaluating the corrosion resistance and porosity of the surface.

Effect of process parameters on surface roughness of 316L stainless steel coated 3D printed PLA parts

3D printing is a novel and rapid emerging technology. Among distinct 3D printing techniques, Fusion deposition modeling (FDM) is one of the cost effective 3D printing technique. In addition, in FDM process, polylactic acid (PLA) filaments are generally utilized. However, the quality of FDM fabricated part depends upon many processing parameters. Hence, in the current investigation PLA samples have been fabricated using FDM at distinct parameters. Further, the fabricated samples were coated at different levels (50 µm, 100 µm and 150 µm) with 316L stainless steel using electric arc spray. Finally, the surface roughness of the fabricated samples was measured. The result showed that the, surface roughness is higher (14.9 µm) at raster orientation (30°), top and bottom layer (2), and coating thickness (50 µm). On the other hand the surface roughness was found to be lower at raster orientation (60°), top and bottom layer (4), and coating thickness (150 µm).

Use of steel gas thermal coatings to increase wear resistance of parts

The process of gas-thermal spraying of coatings made of wire materials has been studied by determining rational regimes to increase the wear resistance of surfaces of vehicle parts. It is determined that the main factors influencing the wear resistance of steel gas-thermal coatings are the cooling rate of steel and the concentration of alloying elements. It is shown that in order to obtain wear-resistant sprayed coatings from alloyed structural steels it is necessary to achieve certain conditions of coating formation, namely: heating and spraying temperature of wire, cooling rate of molten particles, and their oxidation state. One of the most probable reasons for increasing wear resistance is the saturation of the melt droplets with alloying elements (primarily chromium) and impurities of introduction (carbon, nitrogen) in the process of melting the wire in the flame. The relatively low flight speed of molten steel particles and the high concentration of propane-containing carbon in the combustion products contribute to the deep saturation of the melt droplets with carbon. It is likely that these circumstances are associated with the process of increasing the wear resistance of coatings obtained by gas-flame and electric arc spraying. An additional factor that increases the wear resistance of the sprayed coating may be the saturation of the melt droplets with carbon in the process of melting and spraying using propane flames. Studies have suggested that both for the method of gas-flame spraying and for the method of electric arc spraying, there are modes and steels for spraying, which can increase the wear resistance of the coating. On the basis of the conducted researches technologies of strengthening and restoration of details of vehicles by drawing wear-proof coverings are offered.

УМОВИ ЕКСПЛУАТАЦІЇ, ПРИЧИНИ І ВИДИ ЗНОШУВАННЯ ВАЛІВ ДВИГУНІВ ВНУТРІШНЬОГО ЗГОРЯННЯ І ПІДВИЩЕННЯ ЇХ ЗНОСОСТІЙКОСТІ І ТЕРМІНУ СЛУЖБИ

The article considers the direction of energy saving which can be solved during the introduction of surface hardening technologies. Purpose: to create a method of forming wear-resistant coatings by electric arc spraying (EDN) and to establish the impact of its technological modes on the properties of coatings, to improve performance (wear resistance) and service life of motor shafts. Object of research – the process of coating parts such as «shaft» by EDN. The study consisted of the following stages: 1) analysis of the operating conditions of parts such as «shaft» of engines, the establishment of their main defects and ways to eliminate them. Choice of recovery method and its characteristics; 2) study of the properties of the restored surfaces of shafts with coatings: porosity, adhesive and cohesive strength of the coating system-detail, durability, microhardness and wear resistance; 3) optimization of the EDN mode of coatings and development of the technological process of shaft restoration and practical recommendations. Mathematical models have been developed that describe the relationship of technological parameters of the coating process with their properties and the optimal process parameters that provide the necessary properties of coatings have been determined.

Dependence of the elastic modulus of powder coatings on their porosity in electrical contact hardening

The relationship between the elastic modulus and the porosity of powder coatings has been investigated for different methods of their deposition. Porosity is the main means of assessing the quality of coatings and depends on the techniques for their production. A decrease in the elastic modulus of coatings after gas flame spraying is due to the presence of porosity to 30%, and after electric arc spraying – to 20%. The electric contact method of forming coatings makes it possible to reduce porosity to 5-6% and so to bring the value of the elastic modulus of coatings closer to that of compact materials

Use of structural anomalies in steel gas-thermal coatings during increased wear-out

The structure of gas-thermal coatings made of wire materials has been studied by determining the most efficient methods of controlling the process of structure formation to achieve the highest physical and mechanical properties of renewable surfaces of vehicle parts. The effect of formation of anomaly amount of residual austenite in sprayed steel coatings was established. Technologies of application of the “austenitic effect” is suggested here to increase a coating wear-resistance. It is determined that the main factors influencing the content of residual austenite in hardened steel are the cooling rate of steel, the concentration of alloying elements in the austenitic phase, as well as thermal stabilization of austenite during self-tempering. It is shown that to ensure the formation in the structure of sprayed coatings of alloy structural, tool and corrosion-resistant steels of metastable austenite, which has a low flow temperature of deformation gamma-alpha transformation, which corresponds to the operating temperatures of sliding friction units, it is necessary to achieve certain coating conditions. wire spraying, cooling rate of molten particles and the degree of their oxidation). One of the most probable reasons for the appearance of the "austenitic effect" in coatings is the heating of the surface layer to a temperature that promotes thermal stabilization of austenite, as well as saturation of melt droplets with alloying elements (primarily chromium) and impurities (carbon, nitrogen) in flames. The relatively low flight speed of molten steel particles and the high concentration of propane containing carbon in the combustion products contribute to the deep saturation of the melt droplets with carbon. It is likely that these circumstances are associated with a high content of residual austenite in the coatings obtained by gas-flame spraying. An additional factor that increases the resistance of austenite in the sprayed coating may be the saturation of the droplets of the melt with carbon during melting and spraying using a propane flame. The studies under discussion have suggested that both for the method of gas-flame spraying and for the method of electric arc spraying, there are modes and steels for spraying that allow the formation of large amounts of metastable austenite in coatings, which in the process of tribocoupling will turn into martensite.On the basis of the carried-out researches technologies of restoration of details of vehicles by drawing multipurpose coverings in which the choice of a method of heating of a wire at spraying is carried out depending on temperature of the beginning of martensitic transformation of a wire material are offered.

Cloud system for decision supporting of technological process of restoration of surfaces of structures and machine parts

The object of research is the process of decision support of the technological process. The subject of the research is the decision support system of the technological process of restoration of surfaces of structures and machine parts in the form of cloud service. The purpose of the work is to develop a decision support system for the technological process of restoration of surfaces of structures and machine parts in the form of cloud service, which will further optimize high-tech processes of enterprises of various scales using cloud information technology. As a result of the research, the difficulties of automating the design of technological processes are analyzed, mainly due to the fact that the tasks of technological process design do not currently have formal methods of solution. Therefore, for the implementation of technological design, the development of formalization of technology (or part of it), ie the replacement (transformation) of meaningful proposals by the mathematical apparatus. As a result of this formalization, a scheme of information flow in the process of process optimization is proposed. the model of realization of structure of technological process for which the basic input parameters are defined is developed: the list of parameters influencing process. The structure of the expert system for optimization of technological processes was also proposed, the methods of knowledge presentation were analyzed and the scheme of information flows during the implementation of this expert system was developed accordingly. Based on the considered and developed methods and mechanisms used for the development of technological processes, the structure of the information cloud decision support system for automation of the creation of optimized technological processes has been developed. Using the developed methods and models, as a result of the process of process optimization according to acceptable heuristic rules, it was possible to obtain a set of chains of separately optimized technological processes, from which multicriteria selection that meets the optimization requirements. The user of the system can receive in return both one card of technological process, and some best. Conclusions. The developed approaches to the optimization of technological processes were applied to solve the problem of optimization of the technological process of electric arc processing. First, the technological process of electric arc processing was formalized. After that, the formation of heuristic rules and knowledge base of the structure of the technological process of electric arc spraying and accordingly developed the structure of the knowledge base of this technological process and a diagram of the use of the developed information system in the form of cloud service.

Research of surface layer properties of piston rings after gas thermal spraying

Today, one of the important problems of mechanical engineering is to increase the reliability and durability of machines. A special place in this matter is occupied by increasing the wear resistance of parts. As for diesel construction, the problem of increasing the hardness and wear resistance of piston rings is very important. Goal. The goal is study of the structure and nature of changes in the hardness of the surface layer obtained by gas-thermal combined spraying, after grinding, running-in and mileage of the diesel engine, i. e., at all stages of the production cycle. Methodology. The coating on the rings was applied by the method of two-wire metallization with independent supply of wires made of 11X18M steel and molybdenum. Metallographic analysis was used to study the structure of the obtained coating. The condition of the surface layer after coating, grinding, running-in and diesel run was studied by measuring the microhardness. Results. Metallographic analysis of the interface between steel and molybdenum coating – cast iron for many rings and different parts of one ring shows that the coating interacts closely with the substrate along the entire application profile. The structure of molybdenum particles demonstrates their fineness. This is due to the fact that the rapid crystallization under pressure contributes to the creation of a fine-grained structure. Comparison of the microhardness of molybdenum and steel wires with steel-molybdenum coating indicates a significant strengthening of molybdenum and steel particles during spraying, due to the processes of structure formation. Experimental data indicate the stability of the hardness of both molybdenum particles and steel particles, which is important for the coating in operation. Originality. Features of formation of a gas-thermal covering at a simultaneous electric arc spraying of molybdenum and 11Х18М steel on piston rings from pig-iron are established. It is shown that a layered structure is formed, which consists mainly of steel and molybdenum particles. The reasons for the wide range of properties of steel and molybdenum particles have been clarified. It is proved that the operational properties of steel-molybdenum coating are due to its antifriction properties, porosity, which provides self-lubrication of the friction surface, good adhesion to the substrate, which increases by 3–4 times compared to traditional methods. Practical value. The proposed technology of gas-thermal spraying significantly increases the service life of piston rings operating in wear conditions.

Arc discharge sputtering model of Mg–Al–C anode for the nanoceramics production

Using the plasma method of electric arc spraying in helium at pressure of 25 Torr, Mg–Al–C nanocomposites were obtained, which, when calcined, form hollow spherical nanoparticles of aluminum and magnesium dialuminate oxides with sizes of 20 and 80 nm, respectively, and aluminum nanoparticles with a size of 70 nm coated with an oxide layer. The latter ones presence in the electric arc soot is explained by the droplet material entrainment from the evaporating electrode surface. It is shown that the arc discharge is not effective for the formation of alloys of materials with significantly different saturated vapor pressures, but it can be effectively used to create nanoparticles with a shell-core structure.

Исследование химического состава пленок, полученных методом электродугового распыления графита и титана из двух источников

A promising material for cold cathodes creation are carbon films with both acceptable emission properties and satisfactory adhesion to the substrate. It is known that inclusions of metallic elements (chromium, titanium, etc.) improve the adhesion of the carbon film to the substrate. One of the methods for producing coatings based on carbon and titanium is electric arc spraying of a Ti/C composite cathode in an argon atmosphere. The disadvantage of this method is the presence in the total plasma flow of carbon microparticles, which are sources of structural defects in the growing film. Magnetic separation of carbon plasma solves the above problem. In this work, composite metal-carbon films were obtained by simultaneous electric arc spraying of graphite in a magnetic field and of titanium from two evaporators. The composition of the films was studied by Raman spectroscopy (RS) and X-ray photoelectron spectroscopy (XPS). It has been established that the samples obtained are composite films consisting of graphite nanoparticles, Ti14C13 nanoclusters or Ti8C12, titanium oxides, and titanium carbide TiCxN1–x compounds.

Improving the reliability of power complex equipment by electric arc spraying

The Paton Welding Journal, 2021, №10. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

Thermodynamic Estimation of the Parameters for the C–H–O–N–Me-Systems as Operating Fluid Simulants for New Processes of Powder Thermal Spraying and Spheroidizing

Over the past few years, a group of new processes was developed for high-temperature, including plasma electric arc spraying (at ambient pressure) and spheroidizing of some ceramic and metal powder materials with the use of gaseous hydrocarbons in the heat carriers as well as with feeding of organic additions into a high-temperature jet, in particular, polymeric ones, to control porosity of sprayed metallic functional coatings. The paper considers the possibility to modify such technological processes by introducing solid fuel additions of a polymer type into the operating fluid of an apparatus for gasthermal (plasma or other) treatment, which provides melting of metal or oxide powders. For this, with the help of thermodynamic analysis, the processes have been evaluated at temperatures (300–3000) K for the set of such reacting five component systems as C–H–O–N–Me (at ambient pressure 0.101 MPa) with five variants of Ме – aluminum, titanium, chrome, copper, nickel. This makes it possible to consider these systems as simulants for potential technologies for the treatment of oxide powders (Al2O3, TiO2, Cr2O3) as well as metallic ones (Cu, Ni and their alloys). In order to obtain high exothermic contribution to the heating of powders, the combination “air + polymeric addition (polyethylene) of LDPE grade” was chosen as mixed heat carrier (operating fluid) for the basic version of simulated process. During the analysis of equilibria for the considered multicomponent systems (17 variants), a set of following parameters has been used to characterize the energy intensity of the target powder heating process: the equivalence ratio for reacting mixture and its adiabatic temperature; the energy efficiency of material heating with and without taking into account the effect of fuel addition; specific energy consumption for the powder melting; autothermicity degree of the process during the combined heating (electrothermal heating by the arc of plasma torch and heat flux from the “air + solid fuel additions” mixture) of refractory powders. As a result of the assessment, the preferred (from thermodynamic standpoint) regimes of the considered processes have been found and the possibility to realize an energy-efficient heating of these oxide and metal materials (without oxidation of the latter to CuOx, NiO) with a reduced part of the electric channel of energy transfer, resulted from the carrying out of appreciable effect of the fuel-initiated mechanism of heating in the analyzed C–H–O–N–Mesystems, has been shown in the paper.

APPLICATION OF COMBINED TECHNOLOGY FOR RENOVATION AND INCREASED RESOURCE DETAILS OF MEANS OF TRANSPORT

It presents various combinations of primary hardfacing technology for the renovation and improvement of the resource details of ship machinery. Currently, promising are integrated or combined methods hard facing (hybrid technology) coating in conjunction with the modification, the application of multi-layer, multi-functional coatings; development of integrated multioperational technologies. In all conditions, increasing scarcity of expensive alloying materials included in the composition of steels requiring high strength properties of the complex, are promising hybrid technology peening (restore) the surfaces of mild steel Combinations of various primary technologies of application of multipurpose coverings for restoration and increase of a resource of details of knots and units of vehicles are presented. Currently promising are combined methods of application of multifunctional coatings (integrated, hybrid technologies), methods of coating in combination with methods of modification, application of multilayer, multifunctional coatings; development of combined (integrated, hybrid) multioperational technologies. In the conditions of growing shortage of expensive alloying materials which are a part of the steels demanding a high complex of properties of durability, the combined methods of restoration of surfaces are perspective.At present, a methodology for the synthesis of combined multi-operational technologies has not been developed. An empirical-intuitive approach prevails in the combination of multifunctional coating restoration methods. The optimal choice of restoration methods and their sequence is determined by the increase of hardness, complex of mechanical properties, wear resistance, as well as the roughness of the restored surface and the accuracy of the dimensions of the restored part. In the first-best case of combined (hybrid) methods of recovery, the criterion of choice is the comparison of costs and increase the set of mechanical properties of the recoverable parts of components and units of vehicles [13-14]. Each method of recovery has its niche of optimal conditions of use, including even the technological traditions that have developed in a particular enterprise. The decisive factor in the choice of primary methods of applying multifunctional coatings in the combined restoration process is the presence of certain types of equipment at the enterprise and the ability to integrate them intoa single technological cycle. In order to restore vehicle parts with multifunctional coatings with high adhesion strength, hardness and wear resistance, we have proposed a combined (integrated) technology that includes electric arc spraying, electrospark doping and pulsed ion nitriding.

Airflow Dynamics and Aluminum Coating Oxidation Behavior under Electric-Arc Spraying with Airflow Pulsations

The paper aims to investigate the airflow dynamics of electric-arc spraying (EAS) with airflow pulsation. The study is focused on the dynamic structure of the airflow with an obstacle in the form of crossed electrodes at the steady and the pulsating air supply (with a frequency up to 120 Hz). The work was fulfilled using a computer simulation, the airflow “shadow” photo visualization, and the microstructure characterization of the coatings formed. It was found that when air flows along the crossed electrodes with a gap of 2 mm, a depression zone appears in the flow with a pressure drop from 0.56 MPa to 0.01 MPa. The air pulsation resulted in a change in a flow’s dynamic structure towards an increase in the length of the depression zone, which covers most of the arc, affecting the liquid metal oxidation. It is established that the frequency of a droplet formation should match the frequency of the airflow pulsation to minimize the metal oxidation. With the air pulsating at about 65 Hz, the oxide volume fraction in the aluminum coating was reduced by 3.6 times compared to the steady airflow. EAS with airflow pulsation has the potential for technological cost reduction.

Determination of adhesion of the coating deposited by arc spraying with pulsation of atomizing air flow

During electric arc spraying, during the transfer of molten metal by air flow, there is a significant burnout of alloying elements with the formation of a large amount of oxides, which negatively affects the adhesion of the coating to the base. A solution to the problem of increasing the adhesion strength by using pulsation of the atomizing air flow is proposed. At the optimal frequency of the pulsed flow shut-off, the time of formation of liquid metal droplets at the ends of the electrodes coincides with the frequency of pulses of the spraying flow. As a result, the droplets acquire an optimal size, they are transported by an air flow with conservation of energy, a lower mass of oxygen and, as a consequence, a significant decrease in the oxidation of alloying elements in the sprayed material. The existing test methods of sprayed coatings for adhesion strength to the base are analyzed. The design of a modernized device for determining the adhesion strength is developed and described, which provides complex loading of the coating with a combination of tear-off and shear. The tests revealed a significant (up to two times) increase in the adhesion strength of aluminum, zinc-aluminum and steel (Sv08A) coatings applied with air pulsation. This is achieved by increasing the number of fusion zones of the coating particles between themselves and with the base. It is shown that the effect of the pulsation frequency on the adhesion strength changes along a curve with a maximum corresponding to a frequency of 70–80 Hz, regardless of the coating material. It has been established that the aluminum coating has an increased tendency to oxidation, as a result of which it is 15–20 % inferior to the zinc-aluminum coating in adhesion strength. The data obtained substantiate the use of the proposed spraying technology in production

Use of pulsed spray airflow for electric arc spraying of different types of wires

The object of research is the control of the process of formation of a spraying air flow and the transfer of particles of liquid metal from electrodes during arc spraying. One of the problem areas of the arc spraying process is the oxidation of the sprayed metal particles by the oxygen of the air flow during their transportation to the sprayed surface. This leads to the formation of a sufficiently large amount of oxides of chemical elements, which significantly deteriorate the adhesion strength and burn out alloying elements that are necessary to obtain a wear-resistant and corrosion-resistant coating. The suitability and durability of coatings during use depends on the strength of adhesion to the substrate. In the course of the study, methods were used to determine the adhesion strength of the coating to the base – the Steffens method and methods for studying the microstructure of coatings were taken as the basis. The data was processed and dependencies were plotted. The proposed method makes it possible to improve the quality of the resulting coating in terms of such an indicator as improvements in chemical composition. And also to influence the chemical composition by controlling the process of transfer of molten metal using a pulsating air flow. The obtained results of approbation of the method allow us to consider it effective, as evidenced by the quality of the obtained coatings. This is due to the fact that the correctness of the formulation and solution of the problem provided adequate results. In contrast to the existing methods, the proposed one makes it possible to significantly influence the amount of harmful oxygen involved in the formation of a sprayed coating, which makes it possible to obtain a sprayed layer with the required performance characteristics. And also allows to improve its quality without significant capital costs. In addition, the issues of resource and energy saving are being addressed, since the burnout of chemical elements decreases and the air consumption during arc metallization decreases. To solve this problem, a simple design of the pulsator is proposed, which provides the ability to control the spray flow by adjusting the level of overlapping of the holes.