Electric Arc Spraying Research Articles

Effect of heat treatment on the mechanical properties of stainless steel wire

The article is devoted to the study of the mechanical properties of austenitic stainless steel wire with a diameter of 1 mm after heat treatment. Mechanical properties were tested: strength and ductility of hardened and normalized stainless steel. According to the test results, it was found that heat treatment of steel allows obtaining maximum plasticity, while low strength, thus, it seems possible to use this heat treatment as a preparatory operation for the subsequent electric arc spraying of the wire and obtaining a spherical powder.

FORMATION OF COMPOSITE METAL-CERAMIC AND METAL-CARBIDE ELECTRIC ARC SPRAYED COATINGS

The paper studies the possibility of forming composite metal-ceramic (Sv-08G2S-О-Al2O3) and metal-carbide (Sv-08G2S-О-TiC) electric arc sprayed coatings using a hardening phase in the form of powder particles in a free form. For this, a modernized cap of the spray head of an EM-14M electric arc spray gun was used, equipped with a unit for continuous powder feed supply. A laboratory batch of samples was obtained in various technological modes of spraying. Microstructures of the deposited coatings are investigated using a scanning electron microscope. It has been established that composite coatings are characterized by a lamellar structure and a rather low porosity from 8 to 12% (depending on the deposition mode and the hardening phase content), and phase particles of different shades are well differentiated in the structure. The phases were identified by their microhardness indicators. It has been established that the microhardness of the metal matrix (Sv-08G2S-О) is 1.88GPa, ceramic Al2O3 particles ‑ 17.1GPa, TiC particles‑ 31GPa. The influence of the technological parameters of spraying, namely: current, voltage and powder consumption on the content of the hardening phase in the structure of the composite electric arc coatings has been investigated. It was found that when using the maximum values of technological parameters (current 160A, voltage 35V and powder consumption 35 g/min), the maximum content of the hardening phase in the coatings is obtained: 10.3% Al2O3 in metal-ceramic and 25.6% TiC in metal-carbide. The significantly higher maximum TiC content in comparison with the Al2O3 content in composite coatings is explained by the high density of carbide and, as a consequence, the increased velocity of these particles in the high-temperature heterophase jet. Experimental studies of the influence of the content of the strengthening phase in composite coatings on their bond strength to the substrate have been carried out. It is shown that the maximum value of the bond strength of metal-ceramic coatings is 30 MPa and corresponds to the Al2O3 content of 8.7%. As for metal-carbide coatings, the maximum bond strength value of 32 MPa was obtained with a carbide phase content of 18.4%. At the same time, the bond strength of the convention coating sprayed of Sv-08G2S-О wire is 26 MPa. An increase in this characteristic for composite coatings is explained by the additional activation of the sprayed surface by unmelted solid particles of Al2O3 and TiC. It is shown that the decrease in bond strength with an increase in Al2O3 content to 10.3%, and TiC to 25.2% is explained by a significant decrease in the actual contact area of the coating with the substrate.

Electric arc spraying of intermetalic Fe–Al coatings using different solid and powder wires

Electric arc spraying of intermetalic Fe–Al coatings using different solid and powder wires

Study influence factors of the spraying process on the properties of electric arc spraying coatings

The paper considers possibilities to increase the wear resistance, corrosion resistance, and service life for parts machines and mechanisms via their hardening and renovating using electric arc coatings characterized by high density, adhesion strength, and micro hardness thanks to activation of the spraying process. Also, the possibility of controlling the properties of restored surfaces owing to choice of the related equipment with required structure and characteristics in order to prolong the service life of machinery parts is shown. The right choice of equipment for spraying makes it possible to increase the speed and temperature of the spraying gas and particles, reduce the droplet diameter, increase the density and reduce the oxidation of coatings. The influence of spray factors such as the flow rate and pressure of working gases, composition of combustion mixture, spraying distance, dispersion of the spray, properties of wire material, etc. on the properties of the coatings obtained has been investigated. The possibility of controlling the properties of surfaces owing to choice with required characteristics electric arc coatings is shown. The influence of spray factors such as the flow rate and pressure of working gases, composition of combustion mixture, spraying distance, dispersion of the spray, properties of wire material, etc. on the properties of the coatings obtained has been investigated. The use of coatings makes it possible to increase the wear and corrosion resistance of working surfaces of machine parts and mechanisms, in particular ship parts, and so to reduce the costs of alloyed steels and alloys. The coatings application is associated with implementation of a fundamentally new approach, according to which the strength and carrying capacity of a part is provided by its basic material, whereas the resistance to corrosion, wear, and other factors may be increased via using hardening protective coatings. There are many alternative methods for producing coatings, from which it is advisable to choose an optimal, easy to implement, and inexpensive one. Of the variety of methods for hardening coating deposition, the most common technologies used to restore and improve the performance properties of parts are gas-thermal spraying techniques, among which the cheapest and simplest method is electric arc spraying (EAS), whose current improvement is aimed at modifying and activating the spraying process. Such combined technologies do not require additional expensive equipment and operations, which predetermines a reduction in the cost of hardening processes.

Powder wires for resource-saving electric arc spraying

One of the promising methods of thermal spraying is the arc spraying. The use of electric arc spraying is particularly eff ective for the protection of metal structures from corrosion, receiving heat resistant, heat-resistant and wear-resistant coatings. This method is also eff ective in the recovery and hardening de tackles tractors, trucks and agricultural machinery. Signifi cantly extend the scope of the arc deposition can be using the new electrode materials in the form of fl ux-cored wires, the cost of which can be reduced by using materials for dying as a band , with factories producing cable products and iron shavings tion of machine-building enterprises.

Electric arc spraying of cermet coatings of steel 65G-Tic system

Purpose. Substantiation of the possibility of obtaining composite cermet electric arc coatings using TiC powder as a strengthening phase, determination of their physical and mechanical properties. Methodology. The microstructure of the composite cermet electric arc coatings was studied by computer metallography using a ZEISS Gemini SEM 500 scanning electron microscope. The chemical composition was determined by X-ray spectral analysis; phases were identified by measuring their microhardness on a PMT-3 device. The bond strength of the obtained coatings was determined by the method of pulling out the pintle on a tensile testing machine UMM-5. Findings. Composite cermet coatings of the steel 65G-TiC system were obtained by the electric arc spraying using TiC powder in a free state. The influence of the technological parameters of spraying on the amount of the carbide phase in the coating was established, and their microstructure was investigated. The porosity, microhardness of the phases in the coating and its bond strength were determined. Originality. For the first time, composite cermet electric arc coatings of the steel 65G-TiC system were obtained by using a powder of strengthening phase in a free state. Their microstructure, microhardness and bond strength were investigated. The technological spraying modes of electric arc coatings have been established, which provide the optimal content of the strengthening phase to achieve their maximum bond strength with substrate. Practical value. The application of the research results obtained in the work, namely, the determination of the optimal technological parameters of spraying for the formation of cermet electric arc coatings with the maximum level of physical, mechanical and operational properties, makes it possible to meet the requirements for the restoration and hardening of worn surfaces. This leads to an increase in the service life of parts not only in mining, but also in other industries.

Evaluation on the Corrosion and Wear Properties of C-Fibers Doped Aluminum Coatings Obtained Using Arc Spray Technolgoy

Aiming at the wear and corrosion problems of fittings in 500-kV power transmission lines, a functional aluminum-based coating is prepared by an electric arc spraying process and self-made aluminum-based powder-cored wire. The experimental results showed that the friction coefficient of the coating is reduced from 0.4 to 0.2 after adding carbon fiber and that the wear rate is reduced from 2 × 10−3 to 8 × 10−4 mm3/(N·m). The electrochemical behavior of the composite coating is similar to that of the pure aluminum coating. After a 720-h salt spray test, there is no obvious corrosion products on the coating surface, and the thickness of the corrosion layer is only 29 μm. The new composite coating not only has a good anti-wear effect, but also maintains good corrosion resistance of the aluminum coating.

Supercapacitor behavior of carbon‐manganese oxides nanocomposites synthesized by carbon arc

The Mn-C-O composites were synthesized by the electric-arc discharge method. The composite materials were obtained by spraying of graphite electrode with the addition of MnO2. The morphology of Mn-C-O composites formed during electric-arc spraying of metal-carbon electrodes in various buffer gases (N2 and He) and the effect of their subsequent annealing in an oxygen-containing atmosphere was studied. It was experimentally determined that MnOx (MnO, Mn3O4) nanoparticles are mainly formed in N2 atmosphere, and Mn7C3 carbide nanoparticles are formed in He atmosphere. This phenomenon is explained by different cooling rates of the formed composites. With further annealing of materials, partial oxidation of nanoparticles and graphitization of the carbon matrix occur due to the thermal effect of the oxidation reaction. According to the study of electrochemical activity of materials in the 1 M KOH aqueous electrolyte, the materials with a higher MnO content and a higher degree of soot graphitization have the highest electrochemical capacity of 135 Fg−1.

Effect of spraying parameters on surface roughness, deposition efficiency, and microstructure of electric arc sprayed brass coating

Thermal, chemical, and metallurgical surface treatment techniques are being applied to give materials the desirable properties for numerous applications in service. Nowadays, electric arc spraying of copper alloys has gained importance in surface engineering owing to their excellent mechanical properties. However, electric arc sprayed metallic coating usually has high coating roughness and low deposition efficiency upon adherence to the substrate. In this article, the brass coating was deposited onto a mild steel substrate using a twin wire arc spraying technique. The spraying parameters current, voltage, and spray off distance were varied during the deposition process. To gain an understanding, the effect of these spraying parameters on the characteristics of the coating was investigated in terms of its surface roughness, deposition efficiency, and microstructure. The primary purpose of this research is to optimize the process in terms of coating roughness and deposition efficiency. Based on the results obtained, it was observed that an increase in voltage and spray off distance resulted in an increase in coating roughness, whilst an increase in current resulted in a decrease in coating roughness. Deposition efficiency was also greatly affected by the process parameters and decreased significantly with the longer spray off distance. Furthermore, the deposition efficiency increased with the decrease in surface roughness and vice versa. The best results in terms of low coating roughness, high deposition efficiency, and optimized microstructure were found at 24V, 240A, and 100 mm. The use of small diameter feedstock, supersonic nozzle incorporated in equipment, better surface preparation, and optimized process parameters gave better results as compared to the previous study in the field of electric arc spray coating.

INVESTIGATION OF FACTORS, DETERMINING DISPERSITY OF COATING PARTICLES AT ARC SPUTTERING WITH PULSATING SPRAYING STREAM

The essence of the process of electric arc spraying, consists in melting the electrodes with an electric arc and continuous separation of the liquid metal formed at the ends of the electrodes, a stream of compressed air and dispersing it on the sprayed surfaceTo use the periodic removal of pulsating air flow of liquid metal from the ends of the electrodes, it is important to solve the problem of guaranteeing the exclusion of short circuits of electrodes in the complete absence of spray flow and constant continuous supply of electrodes to the combustion zone of the arc. short circuit and when the spray flow is turned on after a pause will ensure the separation and transportation of liquid metal from the ends of the electrodes on the sprayed surface.It is important to determine the optimal mass of liquid metal and the time of formation of a drop of liquid metal depending on the technological parameters of the sprayed electrodes and the energy level of the arc that melts the electrodes.Studies of the determining factors of this process, namely the parameters of the electric arc mode, diameter, material and feed rate of the electrodes are presented.

Characterization of spherical stainless steel powders prepared by electric arc spraying process

Spherical powders were obtained by electric arc spraying of stainless-steel wire. The effect of the electrical power during the arc spraying process was investigated. The fractional composition of the obtained powder was determined by laser diffractometry. Scanning Auger microprobe was used to study surface morphology of the powder particles. The obtained spherical stainless-steel powders will be used to fabricate products by additive manufacturing methods.

Research and development of the inert gas atomization of the wire by means of arc spraying

The paper presents brief information on the theory and technology of electric arc wire spraying. The construction for spraying of four groups of wire materials is shown. Carbon and stainless steel, pure copper and titanium wires were atomized. A model of wire atomization during process of electric arc spraying is described.

Characterization of Fly Ash and a Protective Coating for Brazilian Thermal Power Plant Boilers

Thermoelectric power plants that use mineral coal show high wear in heat exchanger due to the action of several damage mechanisms associated with the impact of hard particles from the residue of burnt coal, the ashes. The employment of coatings should be given into consideration particularly for critical components, which are subject to severe erosive conditions is one of the solutions. However, the choice of material will depend on several factors, including the properties of aggressive ashes. This paper aims to characterize ashes generated by a Brazilian coal-based power plant and a FeCrNbNi-based metallic coating obtained by the electric arc spraying process. No trace of sulfur content was found in fly ashes and it was defined that wear is mainly related to the impact and energy of hard particles are the leading causes of degradation in coal-fired boiler equipment. According to the assessment, applied coating showed (5 ± 2)% by volume of pores and cracks, with 1.6% of oxides after the spraying process and hardness 35% greater than ash particles. Preliminary results in field operation suggest that the material showed relatively low wear compared to the original substrate and showed great applicability in controlling material deterioration for this purpose.

Вплив складу шихтових матеріалів порошкових дротів на механічні характеристики та корозійну стійкість електродугових покриттів

The influence of charge materials of flux-cored wires on their mechanical characteristics, chemical microheterogeneity and corrosion resistance in an aqueous solution of 3% NaCl was established. It is shown that, in contrast to coatings made of solid wires, coatings sprayed using flux-cored wires (PO) have a high chemical heterogeneity. This is due to the fact that the droplets that disperse from the PD melt and form a coating have different chemical compositions. This is caused by incomplete fusion of the charge and steel shell at the ends of the PD during electric arc spraying of coatings. To reduce the chemical micro-heterogeneity, it is proposed to add powders of ferroalloys FeSi, FeMn and self-flux PG-10H-01 to the charge of powder wire containing chromium, boron, carbon-containing components (Cr, FH, PG-100, B4C, FCB) between the components of the charge, homogenize the melt of PD and, as a consequence, reduce the microheterogeneity of the coatings. The presence of chromium, ferrochrome, ferro-silicon and ferromanganese in the charge of PD 90Х17РГС and PD 75Х19Р3ГС2 determines the minimum chemical microheterogeneity of coatings from these wires and, as a result, ensures their high corrosion resistance, which is close to corrosion steel18. To increase the completeness of fusion of the components of the PD charge between itself and its steel shell, it is proposed to add to the PD charge powders of ferroalloys Fe-Mn, Fe-Si, which have a low melting point, able to interact with refractory components of the charge to form low-temperature eutectics. The addition of ferro-silicon, ferromanganese and self-flux alloy PN-10H-01 powders based on ferrochrobor and ferrochrome provided high hardness of electric arc coatings, low heterogeneity in terms of chromium content in coating lamellae and, as a consequence, high corrosion resistance.

Effect of voltage and spray–off distance of electric-arc spray technique on surface properties of nickel–chrome (Ni–Cr) coating developed on 304L stainless steel

Nickel–chrome coatings are widely used to improve surface properties and service life of engineering components made from different ferrous and non–ferrous alloys. Herein, an attempt has been made to investigate the impact of various voltages ranging from 26–30 V and spray–off distances ranging from 100–300 mm of electric-arc spray technique on the surface properties of Ni–Cr coating developed on 304L stainless steel. Thickness, porosity, surface morphology, surface roughness, and hardness of Ni–Cr coatings were determined to study the impact of deposition parameters. Coating deposition at 26 V exhibited the lowest porosity and the highest percentage of Cr nodules among all samples. The comparison study showed that coating deposit developed at 26 V and 100 mm spray–off distance has a maximum thickness, followed by coating developed at 30 V and 100 mm spray–off distance. This indicated that coating deposit developed at 100 mm spray–off distance results in thicker coatings. Maximum hardness was achieved at 30 V and 300 mm spray–off distance. The shorter spray–off distance revealed that coatings tend to be thicker and harder resulting in longer coating life.

Study of the Possibility of Preparing Pseudo-Alloy Coatings by Gas-Thermal Deposition

Spraying processes for composite pseudo-alloy coatings by plasma and electric-arc methods are analyzed. During performance of the work the effect of interaction of components of mechanical mixtures of powders in a plasma jet and materials of dissimilar wires in the electric-arc method on properties of the coatings obtained is considered. The possibility of preparing pseudo-alloy coatings by plasma and electric-arc spraying is demonstrated. Plasma spraying of mixtures of powders of aluminum oxide and nickel is conducted with a PP-25 plasma torch. Electric-arc spraying is carried out using EM-14M equipment with a combination of copper wire and steel and aluminum wires.

Electric arc synthesis of titanium carbide nanoparticles

The structure of titanium carbide nanoparticles formed at electric arc spraying of composite Ti-C electrodes is studied. It is shown that the size of titanium carbide particles in condensation products varies in the range of 10–50 nm, crystal lattice of nanoparticles corresponds to TiC carbide. Annealing the material in an oxygen-containing atmosphere leads to carbon burnout and oxidation of titanium carbide nanoparticles. The main part of carbon is oxidized in the temperature range of 250–500°C, oxidation of titanium carbide nanoparticles occurs in the range from 320 to 400°C. When annealed to the temperatures of 1000°C, sintering of oxide TiO2 nanoparticles occurs. The proposed method can be used to obtain particles of titanium carbide with a shape close to the TiC crystal.

The effect of chemical interaction on the morphology of metal-carbon composites formed in a graphite arc

This work deals with the analysis of mechanism of nanostructured composite formation at joint electric-arc spraying of graphite electrodes with addition of various elements. It is shown that the morphology of nanoparticles, formed at condensation of carbon vapors with the additive elements that have similar pressures of saturated vapors, can vary significantly. This difference is explained by chemical interaction of an additive element with the carbon matrix.

Modeling Arc Spraying Process for Eccentric Sleeve of Cone Crusher GP 500 Using Computer-Aided Design

This article deals with studying the technology of electric arc spraying of the eccentric body by selection of the copper-steel pseudo-alloy for spraying a covering. The part durability with the placed covering depends on the technology of spraying and the properties of the sprayed material. By increasing the strength of adhesion of the covering to the base it is possible to establish the optimal indicators of the coating mode. It became the main criterion of studying the arc spraying technology from the mathematical point of view.

The Effects of Boron Minerals on the Microstructure and Abrasion Resistance of Babbitt Metal (Sn–Sb–Cu) Used as Coating Materials in Hydroelectric Power Plants

In this study, the microstructure of a new alloy is examined which is created by adding boron oxide (B2O3), boric acid (H3BO3) and kolamanit (Ca2B6O11·5H2O) in certain proportions to the white metals (Sn–Sb–Cu) used in the carrier bearing dies of vertical Francis turbines in hydroelectric power plants. The Babbitt materials were coated with electric arc spray coating method before. Also it is examined that whether the coating material produced as a new alloy is appropriate for applying to die surface. Utility of the new white metal material in carrier bearing dies in hydroelectric power plants has been investigated based on the metallographic structure and wear of the new alloy. While some of the boron elements added to the Babbitt metal have positive results in terms of metallographic and abrasion values, some of the boron elements have negative effects.