Arc Thermal Spray Research Articles

Protection against corrosion by molten salts through aluminum coatings deposited by arc thermal spray on ASTM A53 grade B steel

ASTM A53 steel samples were coated with aluminium by EATS, they report continuity and adherence. Thermal treatment improved their performance against corrosion, because the aluminium inter-diffusions are produced from coating into substrate and iron from substrate into coating. Samples were subjected to molten salts corrosion (20 % Na2SO4 and 80 % V2O5) at range of (400–600)° C. Samples were characterized by SEM-EDS and the morphology of layers were studied, noting good protection of layer deposited and the degradation of coating happened at above fusion temperatures of salts, besides the corrosion rate increases with temperature and decreases with exposition time.

Electromagnetic Shielding Performance of Carbon Black Mixed Concrete with Zn-Al Metal Thermal Spray Coating.

The electromagnetic pulse (EMP) is a destructive phenomenon which harms the building, telecommunication, and IT based infrastructure. Thus, it is required to reduce the effect of EMP using shielding materials. In the present study, we have used different thickness of concrete walls by incorporating 1 and 5 wt% of carbon black, as well as 100 µm thick Zn–Al coating using the arc thermal metal spraying method (ATMSM). The EMP was evaluated using waveguide measurement fixture for shielding performance of the concrete wall in the range of 0.85 to 1 GHz frequency. The results reveal that the maximum value, i.e., 41.60 dB is shown by the 5-300-N specimen before application of Zn–Al coating where the thickness of concrete wall was 300 mm and 5% carbon black. However, once the 100 µm thick Zn–Al coating was applied on concrete specimen, this value was increased up to 89.75 dB. The increase in shielding values around 48 dB after using the Zn–Al coating is attributed to the reflection loss of the metal thermal spray coating. Thus, the Zn–Al coating can be used for EMP application instead of metallic plate.

Effect of Sodium Phosphate and Calcium Nitrate Sealing Treatment on Microstructure and Corrosion Resistance of Wire Arc Sprayed Aluminum Coatings

Aluminum coating was deposited by arc thermal spraying process onto the steel substrate for the corrosion protection in aggressive environment. However, the arc thermal sprayed coating possesses defects in the coating. Thus, it is important to reduce the defects and enhance the corrosion resistance properties of the deposited coating using post-treatment. In the present study, we have used different concentrations of sodium phosphate mono basic (NaH2PO4) with 0.1 molar (M) calcium nitrate [Ca(NO3)2] as post-treatment solution to fill out the defects of the Al coating. It was observed by scanning electron microscopy (SEM) that 1 M NaH2PO4 with 0.1 M Ca(NO3)2 treated sample exhibited 71% reduction in defects compared to as coated samples. X-ray diffraction (XRD) was performed to determine the phases formed on the coating surface after treatments. XRD confirms the formation of sodium aluminum hydrogen phosphate (Na3Al(OH)(HPO4)(PO4)) and brushite (Ca(HPO4)(H2O)2) as composite oxides on the Al coating. Electrochemical results show that 0.5 M NaH2PO4 with 0.1 M Ca(NO3)2 treated sample has exhibited the highest charge transfer resistance and the lowest corrosion current density after 89 days of exposure in 3.5 wt.% NaCl solution. The enhancement in corrosion resistance of 0.5 M NaH2PO4 with 0.1 M Ca(NO3)2 treated sample attributed to the formation of adherent, sparingly soluble, and stable corrosion products. The volume fraction result of the corrosion products formed on 0.5 M NaH2PO4 with 0.1 M Ca(NO3)2 treated sample after 89 days of exposure in 3.5 wt.% NaCl using XRD confirms the highest amount of Bayerite (α-Al(OH)3) deposition, thus, the corrosion rate of this sample was the lowest.

Sodium Phosphate Post-treatment on Al Coating: Morphological and Corrosion Study

The coatings deposited by arc thermal spraying process possess defects and pores within the coating, which must be filled using a proper pore sealing agent. In the present study, we have deposited an Al coating on a steel substrate using arc thermal spraying. Post-treatment with different concentrations of sodium phosphate monobasic (NaH2PO4) salt solution was then carried out to fill the pores in the Al coating. The scanning electron microscopy results show that NaH2PO4 (SP) at 0.5 M concentration significantly reduces the porosity. When the concentration of NaH2PO4 is less than 0.5 M, the coating contains some pores and defects, whereas post-treatment with 1 M NaH2PO4 leads to the formation of a brittle film with wide cracks on the coating surface. The x-ray diffraction results of the treated coating confirm the formation of sodium aluminum hydrogen phosphate (Na3Al(OH)(HPO4)(PO4) film (SAHP). Electrochemical results obtained in artificial ocean water solution (ASTM D1141) show that treatment of the coating with 0.5 M NaH2PO4 enhanced the corrosion resistance properties for up to 7 days of exposure, but once the exposure periods are extended, the treated coatings exhibited deterioration because SAHP film started to dissolve in aggressive ions, i.e., artificial ocean water solution which makes the solution acidic owing to the formation of hydrogen phosphate and phosphoric acid. The AC sample shows protection after 60 days of exposure in artificial ocean water solution owing to the formation of protective, adherent, and uniform α-Al(OH)3 as corrosion products.

Effect of stand-off distance in thermally sprayed copper coating

ABSTRACTThe present work demonstrates a two-step method to deposit copper over ABS plastic using electric arc thermal spray means. The energy dispersive spectroscopy confirmed the deposition of copper metal. The adhesive strength demonstrates an increasing trend as the stand-off distance increases from 11 to 17 cm, and decreases as the stand-off distance further increases till 23 cm. For surface roughness, porosity and coating thickness, an increasing trend was noticeable as the stand-off distance increases from 11 to 15 cm, and then assumes a decreasing trend till 23 cm of stand-off distance. The surface residual stress demonstrates decreasing course as the stand-off distance increases from 11 to 23 cm. Different factors engaged during the deposition of molten metal droplet on the ABS substrate such as thermal softening, oxide content, particle velocity and cooling rate dictated the characteristic outcome such as adhesive strength, roughness, porosity coating thickness and surface residual stress.

Study on the deposition of stainless steel on polymeric substrates by arc electric thermal spraying

It is known that application areas of plastics can be enlarged by imparting special features such as higher electrical and thermal conductivity by surface metallization of these materials. Still, there are very limited studies on the metal deposition on polymeric substrates by thermal spray process due to various limitations and problems associated with this aspect, although some reports are available on the fabrication and characterization of bonding layers using low melt temperature materials. With this background, this study was taken up with the objectives of deposition of 309L stainless steel on some polymeric substrates (PP, Nylon 66 and PVC) by electric arc thermal spray process through a prior development of a bond coating. This bond coating was based on epoxy resin/micro silica with scattered and packed metal particles anchored over it, which changed the nature of the substrate surface creating a favorable topology for adhesion and scattering of the sprayed particles. Coatings having an average thickness of 129.06 μm of stainless steel and 259.06 μm of bonding layer (epoxy/micro silica) were obtained over a polyvinyl chloride (PVC) substrate, which had the smaller difference of coefficient of thermal expansion with the bond coat. Obtained coating showed good electrical conductivity value. This kind of favorable metallization of plastics could expand its application areas and might be potential candidate to replace expensive metallic or ceramic materials in special applications.

Influence of surface roughness and current intensity on the adhesion of high alloyed steel deposits - obtained by thermal spraying in electric arc

In this paper the surfaces of some steel samples, low alloyed, were covered by electric arc thermal spray with a steel layer, high alloyed, containing FeNiCrSiB-WC/TiC, using a core wire. In order to study the influence of process parameters on obtained deposits, the surface roughness and the intensity of electric current varied on three levels and the rest of the technological parameters were kept constant. The microstructural characteristics, chemical composition, physical and mechanical properties of the obtained deposits were investigated by SEM analysis of microhardness and by X-ray diffraction. The deposition porosity was investigated by optical microscopy. The adhesion of the layers was investigated by the traction test. Studies have shown that by increasing the intensity of the electric current respectively the arc temperature, the deposition porosity decreases by 23,4%, the microhardness HV and the adherence of the samples subjected to the test increases. The FeNiCrSiB-WC/TiC layers, deposited on low alloyed steel support, can be considered as convenient solutions for obtaining hard, wear-resistant surfaces.

Nanomechanical properties of thermal arc sprayed coating using continuous stiffness measurement and artificial neural network

Instrumented indentation continuous stiffness measurement (CSM) method is applied to investigate the nanomechanical properties of the aluminum and zinc arc thermal spray aluminum coating. This study shows that individual component within a multi-phase material can be differentiated through the stiffness characteristic transition in a single indentation. Using this approach, the nanomechanical properties of the individual phases can be isolated and quantified using statistical deconvolution method. This paper further demonstrates that through the use of computational simulation and artificial neural network, the nanomechanical properties can be predicted based on experimental nanoindentation loading and unloading, where the load-unload responses of an individual material phase can be replicated once the nanomechanical properties are made known. This study shows that CSM method is able to predict the material's elasticity and plasticity properties, including elastic modulus, hardness, yield strength and work hardening, of individual aluminum and zinc components of the thermal arc spray coating.

Corrosion mechanism and kinetics of Al-Zn coating deposited by arc thermal spraying process in saline solution at prolong exposure periods

Steel structures significantly degrades owing to corrosion especially in coastal and industrial areas where significant amounts of aggressive ions are present. Therefore, anodic metals such as Al and Zn are used to protect steel. In the present study, we provide insights for the corrosion mechanism and kinetics of Al-Zn pseudo alloy coating deposited on mild steel plate via an arc thermal spraying process in 3.5 wt.% NaCl solution in terms of its improved corrosion resistance properties at prolonged exposure durations. Electrochemical studies including open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) on the deposited coating at longer exposure durations revealed enhanced corrosion resistance properties while the morphology of corrosion products through field emission-scanning electron microscopy (FE-SEM) indicated their compactness and adherence. Furthermore, atomic force microscopy (AFM) confirmed reduced roughness when compared with that of unexposed coating. Additionally, X-ray diffraction (XRD) and Raman spectroscopy results confirmed the formation of protective, adherent, and sparingly soluble Simonkolleite (Zn5(OH)8Cl2.H2O) after 55 d of exposure in 3.5 wt.% NaCl solution. A schematic is proposed that explains the corrosion process of Al–Zn pseudo alloy coating in 3.5 wt.% NaCl solution from the deposition of coating and initiation of corrosion to longer exposure durations.

Arc Thermal Spray NiCr20 Alloy Coating: Fabrication, Sealant, Heat Treatment, Wear, and Corrosion Resistances

This study presents the effect of heat treatment on porosity, phase composition, microhardness, and wear and corrosion resistances of the thermal sprayed NiCr20 coating after sealing with aluminum phosphate. The annealing temperatures were varied in a range of 400 to 1000°C. The obtained results indicated the porosity of coating decreased with increasing the annealing temperature. After treatment at temperatures in range of 800-1000°C, more than 90% of initial pores in the coating were successfully filled with the sealants. The XRD data revealed not only the formation of new phases of other compounds, but also the interaction between coating and sealant. After heat treatment, wear resistance of coating was 12 times higher than that without heat treatment. The corrosion test in H2SO4 solution indicated that the presence of sealant in coatings increased their corrosion resistance. From these findings, application of these NiCr20 coatings to protect steel against wear and corrosion appears very promising.

The microstructures and anti-corrosion behavior of the thermal sprayed Hastelloy C276 coating on substrate of Q235 steel

Hastelloy C276 coating was prepared on the substrate of Q235 steel by arc thermal spraying process. The microstructure, microhardness, thermal shock resistance and anti-corrosion of the coating were investigated. The coating exhibits a layered buildup structure with some pores and unmelted particles appearing. There is a distinct and rough interface between the coating and the substrate which increases the contact area between the coating and the substrate. The coating and the substrate were meshed to each other in the boundary, showing a strong bonding. The coating exhibited a strong thermal shock resistance with the substrate of Q235 steel at 600 °C. The microhardness of the surface of the coating is much higher than the microhardness of the surface of the substrate. Uniform corrosion method of laboratory semi-immersion test was used to test the corrosion resistance of C276 coating. The coating exhibited good corrosion resistance in concentrated HCl with a concentration of 36.5%.

Influence of calcium nitrate on morphology and corrosion characteristics of ammonium phosphate treated Aluminum coating deposited by arc thermal spraying process

In present study Al coating was deposited by arc thermal spraying process thereafter treated with different concentration of Ammonium phosphate mono basic (NH4H2PO4) and 0.1 M calcium nitrate [Ca(NO3)2] to fill the porosity. Impedance values of treated coating was increased at longer duration of exposure in artificial ocean water due to transformation of Brushite and Ammonium Aluminum hydrogen phosphate hydrate into metastable and sparingly soluble gypsum and Aluminum phosphate. 0.1 M Ca(NO3)2 has positive influenced with 1 M NH4H2PO4 on formation of compact and crystalline morphology as well as corrosion resistance of Al coating.

FeCrMnNiCSi Coating on Grey Cast Iron FC 25 Variable Gas Pressure on Thermal Arc Spray Method

One of the important components of motor fuel engine is cylinder liner. There is a compression and friction combustion process with a piston that produces mechanical energy in cylinder liner. This process introduced several problems that often arise, such as wear reducing because the piston is moving back and forth continuously causing gas leakage so that compression pressure is reduced. To prevent such damage it is necessary to coat the metal with other material that has better wear resistance. This study used FeCrMnNiCSi coating material deposited on Gray cast iron FC 25 by thermal arc spray method to analyze the influence of pressure air variation on morphology and mechanical properties. SEM analysis showed that the higher pressure on the coating process results smaller particles thereby decreasing the porosity. Roughness testing also showed a decrease in the higher pressure, at a pressure of 6 bar of 127.333 μm. Microhardness showed that the 6 bar pressure indicating hardness was 639.8 HV. At 6 bar pressure also obtained the highest abrasion resistance value is 29.66 rotation / mg. The value of adhesion strength in the 4 bar pressure variables shows the optimum value compared with other pressure variations of 15.02 MPa.
 Keywords: cylinder liner, thermal arc-spray, pressure ambient

The Properties of Arc-Sprayed Aluminum Coatings on Armor-Grade Steel

This article presents the results of an examination of the properties of arc-sprayed aluminum on alloyed armor-grade steel. Thermal arc spraying was conducted with a EuTronic Arc Spray 4 wire arc sprayer. Aluminum wire 1.6 mm in diameter was used to produce dense, abrasion- and erosion-resistant coatings approx. 1.0 mm thick with and without nickel/5% aluminum-buffered subcoating. Aluminum coatings were characterized in accordance with ASTM G 65-00 abrasion resistance test, ASTM G 76-95 erosion resistance tests, ASTM C 633-01 adhesion strength, HV0.1 hardness tests and metallographic analyses. Results demonstrate properties of arc-sprayed aluminum and aluminum-nickel material coatings that are especially promising in industrial applications where erosion-, abrasion- and corrosion-resistant coating properties are required.

Influence of Zn and Mg Alloying on the Corrosion Resistance Properties of Al Coating Applied by Arc Thermal Spray Process in Simulated Weather Solution

In this study, Al–Zn and Al–Mg coatings were deposited on steel substrates by an arc thermal spray process. X-ray diffraction and scanning electron microscopy were used to characterize the deposited coatings and corrosion products. Open circuit potential (OCP), electrochemical impedance spectroscopy, and potentiodynamic studies were used to assess the corrosion characteristics of these coatings after exposure according to the Society of Automotive Engineers (SAE) J2334 solution of varying durations. This solution simulates an industrial environment and contains chloride and carbonate ions that induce corrosion of the deposited coatings. However, the Al–Mg alloy coating maintained an OCP of approximately − 0.911 V versus Ag/AgCl in the SAE J2334 solution even after 792 h of exposure. This indicates that it protects the steel sacrificially, whereas the Al–Zn coating provides only barrier-type protection through the deposition of corrosion products. The Al–Mg coating acts as a self-healing coating and provides protection by forming Mg6Al2(OH)16CO3 (Al–Mg layered double hydroxides). Mg6Al2(OH)16CO3 has interlocking characteristics with a morphology of plate-like nanostructures and an ion-exchange ability that can improve the corrosion resistance properties of the coating. The presence of Zn in the corrosion products of the Al–Zn coating allows dissolution, but, at the same time, Zn5(OH)6(CO3)2 and Zn6Al2(OH)16CO3 are formed and act to reduce the corrosion rate.

Cyclic oxidation of ASTM A53 grade B steel protected with a chromium alloy via thermal arc spraying

Cyclic oxidation of ASTM A53 grade B steel protected with a chromium alloy via thermal arc spraying

Deposition of Coating to Protect Waste Water Reservoir in Acidic Solution by Arc Thermal Spray Process

The corrosion characteristics of 304 stainless steel (SS) and titanium (Ti) coatings deposited by the arc thermal spray process in pH 4 solution were assessed. The Ti‐sprayed coating exhibits uniform, less porous, and adherent coating morphology compared to the SS‐sprayed coating. The electrochemical study, that is, electrochemical impedance spectroscopy (EIS), revealed that as exposure periods to solution were increased, the polarization resistance (Rp) decreased and the charge transfer resistance (Rct) increased owing to corrosion of the metallic surface and simultaneously at the same time the deposition of oxide films/corrosion on the SS‐sprayed surface, while Ti coating transformed unstable oxides into the stable phase. Potentiodynamic studies confirmed that both sprayed coatings exhibited passive tendency attributed due to the deposition of corrosion products on SS samples, whereas the Ti‐sprayed sample formed passive oxide films. The Ti coating reduced the corrosion rate by more than six times compared to the SS coating after 312 h of exposure to sulfuric acid‐ (H2SO4‐) contaminated water solution, that is, pH 4. Scanning electron microscope (SEM) results confirmed the uniform and globular morphology of the passive film on the Ti coating resulting in reduced corrosion. On the other hand, the corrosion products formed on SS‐sprayed coating exhibit micropores with a net‐like microstructure. X‐ray diffraction (XRD) revealed the presence of the composite oxide film on Ti‐sprayed samples and lepidocrocite (γ‐FeOOH) on the SS‐coated surface. The transformation of TiO and Ti3O into TiO2 (rutile and anatase) and Ti3O5 after 312 h of exposure to H2SO4 acid reveals the improved corrosion resistance properties of Ti‐sprayed coating.

Corrosion protection in saline environment of a carbon steel coated (aluminum & three-layer painting system) by eats

This paper presents a comparative study on corrosion protection of low-carbon steel coated with two different painting systems. The first set of samples was coated with an aluminum layer of primer deposited by Electric Arc Thermal Spray (EATS), after which two additional layers of paint were applied, thereby creating an aluminum-painting system; while the second set of samples was coated with the traditional three-layer painting system (zinc-rich layer of primer). Afterwards, all the samples were exposed to the salt spray chamber. The samples were monitored to record their reactions in the corrosive saline environment. Scanning Electron Microscopy (SEM), adhesion and electrochemical corrosion tests were performed to characterize the coatings and report changes in their properties (adhesion, topography and homogeneity), which are related to exposure time. The three-layer painting system barely complied with manufacturer claims on protection time under corrosive conditions; on the other hand, the aluminum-painting system yielded better results by prolonging protection time.

Study on the Shielding Effectiveness of an Arc Thermal Metal Spraying Method against an Electromagnetic Pulse.

An electromagnetic pulse (EMP) explodes in real-time and causes critical damage within a short period to not only electric devices, but also to national infrastructures. In terms of EMP shielding rooms, metal plate has been used due to its excellent shielding effectiveness (SE). However, it has difficulties in manufacturing, as the fabrication of welded parts of metal plates and the cost of construction are non-economical. The objective of this study is to examine the applicability of the arc thermal metal spraying (ATMS) method as a new EMP shielding method to replace metal plate. The experimental parameters, metal types (Cu, Zn-Al), and coating thickness (100–700 μm) used for the ATMS method were considered. As an experiment, a SE test against an EMP in the range of 103 to 1010 Hz was conducted. Results showed that the ATMS coating with Zn-Al had similar shielding performance in comparison with metal plate. In conclusion, the ATMS method is judged to have a high possibility of actual application as a new EMP shielding material.

The influence of HVOF spraying parameters on the microstructure, residual stress and cavitation resistance of FeMnCrSi coatings

Thermal spray processes can be used to apply erosion-resistant coatings to components. One of the most important is the HVOF (High Velocity Oxygen Fuel) process, which is characterized by lower temperatures and higher projection velocities than arc and plasma thermal spray processes. This study sought to analyze the influence of three process parameters (standoff distance, fuel/oxygen ratio and powder feed rate) on particle velocity, particle temperature, coating microstructure and residual stress formation in FeMnCrSi coatings deposited by a liquid-fuel HVOF process and the effect in turn of coating microstructure and residual stress on coating cavitation resistance. An increase in fuel flow and reduction in standoff distance resulted in increased particle velocity but did not significantly affect particle temperature. Varying the process parameters had a significant influence on the residual stress in the coatings. A correlation between compressive residual stress, increased hardness and reduced mass loss rate during ultrasonic cavitation testing was observed.