Arc Spraying Technology Research Articles

Insight into the Hot Corrosion Behavior of FeMnCrSi/TiC Coatings at 900 °C

This study explores the deposition of an Fe-MnCrSi/TiC coating on 45 steel surfaces using high-velocity arc spraying technology, examining the microstructure and hot corrosion behavior of the resultant layer. The microstructure of the FeMnCrSi/TiC coating primarily consists of an α-Fe (BCC) solid solution, composed of Fe, Mn, Cr, Si, C, and other elements, with a minor presence of β-Fe (FCC) solid-solution phase and unmelted TiC particles. Following 100 h of cyclic 900 °C hot corrosion, Mn on the coating surface preferentially oxidizes, forming a manganese-rich oxide layer. This process reduces the oxygen partial pressure (O2) within the coating, prompting the formation of a dense Cr2O3 layer on the inner side of the oxide layer. Concurrently, the rapid diffusion of Mn and Cr elements triggers the generation of Mn- and Cr-deficient regions at the metal/oxide layer interface, inducing the transformation of the coated metal primary matrix from an FCC + BCC dual phase to an α-Fe (BCC) single phase. After the reaction, the hot corrosion weight gain of the coating reached 12.43 mg/cm2, approximately one-fourteenth of the weight gain of the 45 steel substrates. This weight gain adheres to the parabolic law, suggesting that the FeMnCrSi/TiC coating exhibits excellent corrosion resistance under the given conditions.

Material system and tribological mechanism of plasma sprayed wear resistant coatings: Overview

Challenging environments in aviation, automotive, electric power, and various industrial sectors are increasing industry and technological demands, resulting in machine damage and energy loss from friction and wear between interacting surfaces. Addressing this issue requires the development of new and advanced materials, processing techniques, and surface modification methods to enhance performance and reduce friction and wear. Plasma spraying technology is essential for material surface reinforcement and modification because of its low cost and stability. This paper reviews and summarizes the research progress on plasma spraying wear-resistant coating material systems and tribological mechanisms, covering the working process and principles of plasma spraying equipment. It also details wear-resistant coating material systems, including iron-based, nickel-based, copper-based, other metal materials, oxides, and monoxide ceramic materials.Furthermore, it addresses the wear-resistant and friction-reduction mechanisms of wear-resistant coatings, aiming to summarize the tribological strengthening mechanism concerning wear resistance and friction reduction. Moreover, this paper covers aspects such as powder design, sealing treatment, laser remelting, and other methods for regulating the wear resistance of coatings, examining their influence on the wear resistance of coatings in material design, spraying process, and post-spraying treatment. Plasma spraying wear-resistant coatings should be used along with doping modification and other methods to study the new spraying materials; furthermore, the optimization of the spraying process and post-treatment methods should be investigated to prepare a wear-resistant coating that meets the performance of the actual working conditions. At the same time, ultrahigh temperature wear-resistant coatings and super lubricating coatings are also future research priorities. In addition, when comparing plasma transfer arc spraying technology and plasma enhanced high-speed arc spraying technology with plasma non-transfer arc spraying technology, the jet temperature is higher, and the cost is lower; however, since the process is still in its infancy, the follow-up should be strengthened in this area of technical research. This paper provides a theoretical basis and reference for researching plasma spraying wear-resistant coatings in various fields.

Microstructure and Wear Performance of High-Velocity Arc Sprayed FeMnCrNiBNbAl Coating

In this study, FeMnCrNiBNbAl wear-resistant coatings were prepared via high-velocity arc spraying technology on the surface of Q235 steel. The effects of spraying distance, voltage, and current on the coating performance were studied via the orthogonal experimental method with microhardness and porosity as evaluation indicators, and the process parameters were optimized. The order of primary and secondary factors affecting coating performance were: spraying distance, voltage, and current. The optimized process parameters are: spraying distance 200 mm, voltage 36 V, and current 240 A. The coating prepared using the optimized process parameters has an average microhardness of 756 HV0.1 and an average porosity of 1.03%. The coating mainly consists of α-Fe, Fe-Cr, Ni-Cr-Fe, Al2O3, and (Fe, Ni) solid solution. The coating friction coefficient was 0.5 while that of the substrate was 0.7. The depth and width of the wear marks of the coating were 6.32 µm and 555.41 µm, respectively, which are 66% and 32% lower in comparison with Q235 steel under the same test conditions. The wear forms of this coating were mainly fatigue peeling and adhesive wear.

Experimental study on the characteristics of loop heat pipe with modified carbon fiber felt wick

In order to achieve accurate and effective thermal management of high-performance electronic components, the performance of a small flat loop heat pipe was investigated. A flexible composite capillary wick material has been applied in a flat loop heat pipe. Surface modification of carbon fiber felt was carried out using arc spraying technology to make it a more suitable material for producing capillary wicks. The physical properties of the modified carbon fiber felts were determined by measuring their wettability, porosity, capillary force, and thermal conductivity. A small flat loop heat pipe assembled with carbon fiber felt wick was designed and fabricated, and experimental testing was conducted. The experimental data indicated that the performance of methanol was better than that of acetone and water. The loop heat pipe with a 60% filling ratio maintained the heat source temperature at 84.47 °C under a load of 120 W (30 W/cm2). Conditions where the heat source starts before the cooling system are more favorable for the quick and stable startup of the loop heat pipe. The experimental results demonstrated that the loop heat pipe with a modified carbon fiber felt wick exhibited excellent operational and heat transfer performance.

Hot Corrosion Behavior of TWAS and HVOF NiCr-Based Coatings in Molten Salt.

In order to extend the life of boilers by applying an anti-corrosion coating without the need to dismantle them, it is advisable to find coatings that can be applied using cheaper and portable techniques, such as Twin Wire Arc Spray technology (TWAS). In this study, we compare selected NiCr-based coatings and two uncoated steel substrates (steel 1.7715 and 1.4903). Two coatings, Cr3C2 - 25% NiCr and Hastelloy C-276 are deposited using High velocity oxygen-fuel technology (HVOF) and three coatings, NiCrTi, NiCrMo, and Inconel 625, are deposited using TWAS. In addition to the corrosion weight gain during 50 cycles of loading in an 18% Na2SO4 and 82% Fe2(SO4)3 salt environment at 690 °C evaluated using the gravimetric method, the microstructure and phase composition of the coatings were analyzed on the samples after the exposure in order to compare the properties and gain a deeper understanding of the corrosion kinetics. Coating cross-sections and free-surfaces were observed with a scanning electron microscope (SEM) with an energy-dispersive (EDX) system. The phase composition was investigated using X-ray diffraction (XRD) and Raman spectroscopy. No significant differences were observed between the TWAS and HVOF coating methods for the coatings compared. Due to the similar corrosion products found on all coatings, a very effective corrosion protective layer was formed on the surface, forming a barrier between the corrosive environment and the coating regardless of the used deposition technology. Therefore, for industrial use on the inner surface of coal-fired boilers we recommend NiCrTi, NiCrMo, or Inconel coatings prepared with the more cost-effective and portable TWAS technology.

Friction and anti-corrosion characteristics of arc sprayed Al+Zn coatings on steel structures prepared in atmospheric environment

Al coatings and Al–Zn coatings were prepared on the surface of Q345B steel after shot peening using supersonic arc spraying technology to improve anti-slip and anti-corrosion properties. The SEM, XRD and EDAX were used to detect the surface morphology, coating structure and phase composition of the two coatings. The anti-slip coefficient and anti-wear performance of the two coatings were detected by the anti-slip coefficient detector and the MRTR friction and wear tester, respectively. The anti-corrosion characteristics of the two coatings were obtained by the electrochemical corrosion workstation. The experimental results showed that the thickness of both coatings is 100 μm. The substrate and the coating are mechanically bonded. Under the condition of the test parameters, the anti-slip coefficients of Al coating and Al–Zn coating were 0.717 and 0.823, respectively, satisfying the service requirement of the steel structure. The corrosion potential of the Al–Zn coating was −1.136, which exhibits a good anti-corrosion performance. Under the condition of water, the anti-wear characteristics of Al–Zn were relatively ideal. The wear-resistance of Al–Zn coating is better than that of pure Al coating. In conclusion, Al–Zn coating possesses excellent anti-slip, anti-corrosion and anti-wear characteristics and can be used in large steel structure surface modification.

Comparison of high temperature corrosion resistance of NiCr-based coatings applied by High Velocity Oxygen Fuel and Twin Arc Spray processes

High temperature corrosion in a molten sodium sulfate salt environment is a serious problem of coal-fired boiler components. The promising possibility for surface protection is to apply thermally sprayed coatings. However, the key to success is to choose the optimal material and the proper spraying technology for a given application. Therefore, this study is aimed at a comparison of the high temperature behaviour of two protecting NiCr-based coatings sprayed by different technologies on 1.4903 (W.nr.) chrome-molybdenum steel. NiCrMoWFe was deposited by High Velocity Oxygen Fuel technology (HVOF). Twin wire arc spray technology (TWAS) was used to deposit multi-layered “multicoat” consisting of NiCrMoNbTa and NiCrTi with ceramic overlay Armaguard coated by brush. Chrome-molybdenum steel 1.7715 (W.nr.) commonly used in coal-fired boiler was also exposed to the high temperature corrosion test to evaluate the potential benefit of the coating. Coated as well as the uncoated specimens were exposed to the molten salt environment 18% Na2SO4 and 82% Fe2(SO4)3 at 690 °C under cyclic condition. The thermogravimetric approach was used to determine kinetics of corrosion. The X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) techniques were used to analyze the corrosion products and determine the corrosion mechanism. The results of high temperature corrosion resistance show that NiCrMoWFe coated by HVOF and multicoat sprayed by TWAS was comparable.

Improvement of technology of variable chemical composition layer formation on the product surface

The possibility of forming on the surface of the product by arc deposition a layer with variable chemical composition with a predefined distribution of properties is considered. With the arc deposition of a layer of variable chemical composition, there are some difficulties for obtaining its high quality realization caused by the influence of the molten base metal of the welding pool on the distribution of chemical elements along the length of the deposited layer. When surfacing such layers with the use of ceramic alloying fluxes, there is a limit on the number of alloys that are introduced into the welding pool from the flux without impairing of the surfacing quality. This problem is solved through the use of arc surfacing with a tape electrode, which provides a minimum share of the base metal in the weld, as well as the inclusion of arc spraying technology during the formation of the working layer by arc surfacing, which makes it possible to introduce additional alloying elements into the weld pool. Currently, the process of arc spraying is carried out at equal feed rates of the electrodes in the metallizer. The electrodes have the same chemical composition and the electric arc is supplied with direct or alternating current. A variant of the metallizer design is proposed, which allows controlling the chemical composition of the deposited metal through the use of two electrodes of different chemical composition, while the metallizer has the ability to separately control the feed rates of these electrodes. By adjusting the ratio of the feed rates, while ensuring at a constant level the total mass rate of their melting (feed), one can change the chemical composition of the sprayed layer. The paper presents schemes for the implementation of the metal arc spraying process of a layer with variable chemical composition

The Investigation of Corrosion Property of The Four Coatings in The Transformer Substation Soil

Pure Al coating, AlSi alloy coating, NiAl alloy coating and 316L stainless steel coating were prepared on the Q235 steel by arc spraying technology. The corrosion of the four sprayed alloy coatings in the 220kV transformer substation soil and soil solution was studied by buried specimens and electrochemical test in Hunan. The corrosion behaviors of the coating steel samples in transformer substation soil solution were investigated by line polarization, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests. The results show that the best corrosion resistance of the four sprayed alloy coatings was AlSi coating, sequentially in the order of NiA1 and stainless steel coating, and the Al coating was easy bouffant at long time in the underground, so that the corrosion resistance is not good.

Structure and Tribological Properties of the Wear-Resistant Coatings Deposited Using Flux-Cored Wires Modified by Tantalum and Tungsten

Test flux-cored wires for arc spraying technology are developed. Tantalum and tungsten powders are selected as modifying additives. A PGSR-4 (Ni–Cr–B–Si) commercial powder is the basis of the powder material. The structure of the modified coatings is studied by metallographic analysis. Wear tests of the modified coatings are performed by slipping friction. The friction coefficients and the roughness characteristics are measured.

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.

Microstructure and wear performance of arc-sprayed Al/316L stainless-steel composite coating

To improve the wear resistance of aluminium alloys, an Al/316L stainless-steel composite coating was successfully prepared on an aluminium alloy surface by two-channel-synchronization wire feeding arc spraying technology. The composite coating has a ductile (Al) and hard (stainless-steel) interpenetration structure. The interface between the substrate and the coating was fuzzy owing to the pinning interface of interpenetrating structure and the obvious diffusion layer near the interface, compared with 316L stainless-steel coating. The tribological properties of composite coatings were analysed. The wear resistance of the Al/316L stainless-steel composite coating was shown to be three times higher than that of the stainless-steel coating. The Al/316L stainless-steel composite coatings improved the wear resistance of aluminium alloy by a factor greater than nine. In the composite coating, the addition of Al splats promoted the formation of Fe3O4 and the interpenetrating structures, improving the wear resistance and crack propagation resistance of the coating.

Influence of Oxides on the Performance of Cylinder Bore Coatings of Engine Blocks

The performance of thermally sprayed coatings such as for the inner surface of combustion engines depends on the microstructure and phase composition of the coatings after deposition. These can be varied in a targeted manner to reach the desired coating behavior. One approach might be altering the atomization gas in order to influence the oxide content in the coating. A former study of the authors already showed that the oxide content in the coatings can be influenced effectively by simply changing the atomization gas in case of Plasma Transferred Arc Spray technology. In this study, a systematic approach is followed in order to investigate the effect of oxides on the tribological performance and the corrosion behavior. For this purpose, coatings with different oxide contents were manufactured by taking advantage of different atomization gases. The results of this study confirm that coatings with pronounced oxide‐rich phases exhibit lower friction coefficients and less sever outbreaks in comparison to those without distinctive oxide‐rich phase. The presence of oxide‐rich phases does not influence the corrosion behavior of the coatings significantly, although some minor effects are observed along phase boundaries.

Influence of Ni and Cr on the high-temperature wear resistance of FeNiCrAl coatings

Abstract To reduce the brittleness of Fe-Al intermetallic compound coatings, FeNiCrAl powder wire for high-speed electric arc spraying is developed by integrating Ni and Cr into an Fe-Al intermetallic compound. The corresponding FeNiCrAl coating is prepared via high-speed electric arc spraying technology. A 3Cr13 coating is selected as the material for comparison, and the friction and wear properties of the two coatings are investigated from 200 °C to 800 °C. The friction coefficient variations and friction surface topography patterns of the two coatings are analyzed via X-ray diffractometry (XRD), hardness testing, and scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS). The phase compositions of the materials on the wear surfaces are analyzed via X-ray photoelectron energy spectrometry (XPS). The results show that after the friction coefficient of the FeNiCrAl coating reaches its peak value at 400 °C, it declines with increasing temperature, and its wear volume is less than that of the 3Cr13 coating. An XPS-based wear surface composition analysis and SEM wear scar topography results show that the FeNiCrAl coating produces not only Fe, Ni and Cr oxides but also Ni-Al intermetallic compounds during high-temperature friction. After the friction coefficient of the FeNiCrAl coating reaches its peak at 800 °C, more Al2O3 is formed around the Fe3Al, and these compounds aggregate to form a protective film that effectively prevents further intrusion of O ions. A dense oxide layer covers the wear surface, and the formation of hard-phase chemical compounds improves the wear resistance and bearing capability of the coating.

High-Temperature Oxidation Resistance of NiAl Intermetallic Formed In Situ by Thermal Spraying

An Al/Ni composite coating was deposited on the surface of a pure Ti substrate by arc spray technology and plasma spray technology. In order to enable the in-situ reaction between the Al/Ni composite coating and the specimen, they were heated under different conditions. In addition, oxidation testing was conducted to test the oxidation-resistant property of the coating. The phase transition regulation of the coating after heating, the influence of heating at different temperatures and time on the reaction depth, and the correlated theory of the in-situ formation of the NiAl intermetallic compounds were studied and analyzed. The results showed that after the heat treatment, a ragged wave-like morphology was exhibited in the diffusion front of Al, and a small amount of the Ni in the diffusion region did not participate in the reaction. The growth of the NiAl intermetallic layer in the diffusion region of the Al/Ni/Ti specimen was obviously slower compared with the Al/Ni specimen.

Oxidation Resistance and Modification Reaction Mechanism of Al Coating Sprayed on Pure Ti Substrate

An Al coating was deposited on the surface of pure Ti substrate by arc spray technology. In order to enable the modification reaction between the Al coating and Ti substrate, the specimen was heated to a temperature above the melting point of Al. Oxidation testing of the uncoated Ti and coated specimen was conducted at 1073 K under an air atmosphere. The microstructure, chemical composition, and phase determination of the coatings and interfaces, before and after modification treatment, were done using SEM, EDS, and XRD methods. The relationships between the modification results and time and temperature were discussed. The results showed that, after heating at 973 K for 5 hours, there was still sufficient Al on the surface of the specimen. Only intermetallic TiAl3 was formed in the diffusion region. After heating at 1073 K for 5 hours, all the Al elements diffused into the Ti substrate. Intermetallics TiAl2 and Ti3Al were also formed in the diffusion front of Al, in addition to TiAl3. After heating at 1173 K for 5 hours, a new intermetallic TiAl phase was formed at the interface of TiAl2 and Ti3Al. As the modification reaction time was prolonged at 1173 K, the formation of intermetallics TiAl2, TiAl, and Ti3Al were all increased. Among them, the formation amount of TiAl2 > Ti3Al > TiAl. The specimen after modification treatment had better high temperature oxidation resistance than the pure Ti substrate without coating.

Spray process for in situ synthesizing Ti(C,N)-TiB2-Al2O3 composite ceramic coatings

Using core wires with Ti-B4C-C as core and Al as strip materials, Ti(C,N)-TiB2-Al2O3 composite ceramic coatings were prepared on 45 steel substrates by the reactive arc spray technology. The influence of spray voltage, current, gas pressure and distance on the coatings was discussed. The spray parameters were optimized with porosity of the coatings as evaluation standard. The results showed that the most important factor which influences the quality of the coatings was spray distance. Then spray gas pressure, current and voltage followed in turn. The optimum process was spray current of 120A, voltage of 36, gas pressure of 0.7MPa and distance of 160mm. The porosity of coatings prepared in this spray process was only 2.11%. The coatings were composed of TiB2, TiC0.3N0.7, TiN, Al2O3 and AlN. Good properties and uniform distribution of these ceramic phases made the coatings have excellent comprehensive performances.

Preparation and Properties of Superhydrophobizted Sprayed Zn-Al Coating

A superhydrophobic ZnAl coating was prepared by the electric arc spraying technology and then surface modification by stearic acid/ethanol. The surface wettability, morphology and chemical structure of the ZnAl coating before and after modification were characterized by contact angle measurement(OCA-20), scanning electron microscope(SEM) and artificial FTIR spectrometer(ATR), respectively. The impedance spectrum and polarization curves of the coatings were measuared by electrochemical workstation(Solartron Analytical) with three electrodes system. The results show that the as sprayed ZnAl coating consists of irregular micro-and nano-sized alloy particles and pores, and exhibits clear hydrophilicity, which may be ascribed to the high surface energy of metallic coating. After the surface modification with stearic acid, the static contact angle of the coating reached 153.8° with a rolling angle less than 10°, because there exsited a large number of hydrophobic long alkyl chains on the surface of the modified Zn Al coating. In addition, the surface modification could significantly enhance the corrosion resistance of ZnAl coating due to that the thin hydrophobic film plays an important role in supression of the fall off and dissolution of corrosion products on the ZnAl coating, leading to the increase of charge transfer resistance and the corrosion current density.

Fabrication and characterization of Fe-based amorphous coatings prepared by high-velocity arc spraying

Abstract Fe-based coatings with a high amorphous content were firstly developed by the traditional twin wires arc spray technology. In consideration of empirical rules, including the multi-component system, an optimal concentration of small atoms, negative heat of mixing and an appropriate atom size mismatch among the main components, the cored wires were designed to contain eight elements, which have an optimized atomic volume strain criterion λ n , in range of 0.14–0.21, to render the coatings a high glass forming ability. Then the coatings were prepared using the above-designed cored wires through a rapid arc spray melting and solidification process. Crystalline phases could not be identified from the XRD patterns within the XRD resolution limits, suggesting that the as-sprayed coatings were approximately comprised of fully amorphous phases. With a dense structure and a low porosity of only 2%, the amorphous Fe-based coatings exhibited an attractive combination of high hardness (900–1100 HV 0.3 ) and superior bonding strength (44.9–54.8 MPa). The coating at λ n = 0.21 had the lowest Gibbs free energy difference Δ G , exhibited the largest super-cooled liquid region Δ T x , Lu’s criterion factor γ value and the heat of crystallization (Δ H ) values, which indicating the highest GFA.

Influence of FeCrAl Coating Arc Sprayed on Aluminum Corrosion Resistance of H13 Steel

FeCrAl coating was prepared on the surface of H13 steel through electric arc spraying (EASP) technology. The surface and cross section morphology, elements and phase composition of the composite coating were analyzed by the means of scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The aluminum corrosion resistance was tested by the static hot-dip aluminum method in molten AC4C aluminum at 700°C. The result showed that the FeCrAl coating, of which the microstructure was compact, had typical layer structure, and a small amount of oxide films and pores could be found among the lamellar particles. FeCrAl coating mainly contained Fe-Cr solid solution and small amounts of Al2O3. The weight of H13 corrosion was 3 times as much as that of FeCrAl coating corrosion after static melting treatment for 1h, and the corrosion rate of H13 steel and FeCrAl coating were both increased as the corrosion time increased from 1h to 3h. It was worthy noted that the weight of H13 corrosion was significantly increased, which was 17 times as much as that of FeCrAl coating corrosion.