Arc Spraying Research Articles

The influence of welding modes on metallic structures processed through WAAM

Abstract Wire arc additive manufacturing (WAAM) has emerged as a versatile and cost-effective technique for fabricating complex, large-scale components with enhanced material flexibility. The bead profile, like width, height, and penetration, is critical in WAAM fabrication, influencing the quality and performance of the final component. Consistent and precise profiles are essential for accurate layering and material deposition in complex 3D structures. Various parameters, such as current, voltage, deposition rate, interpass temperature, and welding mode, impact deposit quality in WAAM. This study focuses on implementing a controlled heat input deposition approach, utilizing various welding modes: Control Weld (classic MIG/MAG), Speed Weld (voltage-controlled pulsed arc), Vari Weld (current-controlled pulsed arc), Rapid Weld (high-capacity spray arc), Root Weld (energy-reduced short arc), and Fine Weld (energy-reduced, current-controlled short arc). The study scrutinizes the impact of altering the welding mode on bead profile, bead quality, macroscopic morphology, microstructure, and mechanical properties in single-bead WAAM structures.

Expanding the Applications of Copper-based Alloys by Thermal Arc Spraying

In this article, the case of depositing a Ni-based alloy layer by thermal arc spraying on a copper alloy substrate with cylindrical geometry over its entire surface is presented. After the coating was deposited, the layer was analyzed microstructurally both on the surface and in cross-section, and it was observed that it adhered very well to the substrate. In addition to the high adhesion to the substrate, a low porosity of the coating was observed, which ensures good compactness of the coating. Based on these results, further investigation of the Ni coating can be recommended to limit the toxicity caused by the oxidation of copper and copper alloy heating elements.

Synergism of Arc Spraying, Laser Processing, and Hydrophobization for Long‐Lasting Corrosion Protection of MA8 Magnesium Alloy

Due to a number of unique properties, magnesium and its alloys are attractive for use in mechanical engineering, medicine, aviation, the automotive industry, etc. Unfortunately, the widespread use of these materials is limited by their low corrosion resistance. Traditional surface modification techniques have struggled to simultaneously enhance both the mechanical durability and corrosion resistance of magnesium‐based materials. Herein, a method synergistically combining the advantages of arc spraying, laser processing, and hydrophobization is developed. This finely tuned combination results in the production of an aluminum coating with superhydrophobic properties formed on top of magnesium alloy that has very high mechanical and chemical resistance. The results presented in this article demonstrate that such coatings preserve a constant contact angle exceeding 165° during a year of laboratory storage, withstand long‐lasting humid and salt fog atmosphere, demonstrate corrosion current lower than 3 × 10−8 A cm−2 during 120 days of its continuous contact with chloride‐containing corrosive environments, and preserve the superhydrophobic state after sand abrasion test. The corrosion inhibition mechanisms of the designed coating are discussed. The developed innovative approach addresses a critical challenge in enhancing the corrosion resistance of magnesium‐based materials, paving the way for their broader application across various industrial sectors.

Oxynitrided Ti-6Al-4V Coatings Deposited by Twin Wire Arc Spray for Protection of Aluminum Die-Casting Molds

Steel molds used for aluminum die-casting often fail due to excessive wear or cracking phenomena associated with the soldering effect in contact with molten aluminum, which leads to the formation of iron-based intermetallic compounds and causes problems in the cast components. One solution is to apply protective coatings whose composition is less reactive with the molten aluminum and improve its hardness, toughness, wear, and corrosion resistance, thus prolonging its service life. This work evaluates the effectiveness of Ti-6Al-4V coatings deposited by twin wire arc spraying in an air or nitrogen atmosphere. Nitrogen was used as the carrier and shielding gas for the in-flight molten particles. Coatings were deposited by varying the stand-off distance, the nitrogen gas pressures, and the substrate temperature. The microstructure of the coatings is interlayered, one porous layer of dendrites and one highly densified layer. The presence of TiN, TiO2, α-Ti, and β-Ti phases was confirmed by different characterization methods. For instance, x-ray photoelectron spectroscopy measurements confirmed the presence of N-Ti, O-Ti, and N-O bonds, with the oxygen/nitrogen/titanium percentage associated with the formation of a non-stoichiometric (Ti, Al, V)NxOy phase. Finally, the reactivity of selected oxynitrided Ti-6Al-4V coating in contact with molten aluminum showed a low reaction rate compared to the coarse reaction layer suffered by the uncoated steel substrates.

Thermophysical properties of AlxCoCrCuFeNi high entropy alloys

The AlxCoCrCuFeNi (x = 0.25, 0.5, 1, 2) high entropy alloys (HEAs) were prepared by arc melting and spray casting techniques. Their microstructures, hardness, and thermophysical properties such as fusion enthalpy, entropy, thermal diffusion coefficients, thermal expansion coefficients, were investigated. XRD results indicated that AlxCoCrCuFeNi (x = 0.25 and 0.5) alloys were composed of a high-entropy FCC phase and Cu-rich nanophase. As the Al content increased to 1 and 2, the phase structures included the AlNi-rich B2 phase, FeCr-rich A2 phase and Cu-rich nanophase. With the increased Al content, the microstructures of AlxCoCrCuFeNi HEAs transitioned from coarse dendrites to petal-like dendrites, and the grains were continuously refined. Moreover, the Al additions reduced the density whereas increased the Vickers hardness of the alloys. The maximum hardness observed in Al2CoCrCuFeNi HEA was approximately 2.4 times greater than that of the Al0.25CoCrCuFeNi HEA. The thermal diffusion coefficients of alloys initially increased and subsequently decreased as the temperature elevated. The phase transformation induced by Al content was an effective method for rapidly homogenizing the internal temperature of alloys. Furthermore, the crystal structure, elemental segregation, lattice distortion, enthalpy and entropy of fusion, and lattice vibration frequency all mutually affected the thermal diffusion and expansion coefficients of AlxCoCrCuFeNi HEAs.

Enhancing corrosion resistance of Al alloy sheets with potential gradient by arc-sprayed Zn coatings

To improve the corrosion resistance and wide the application of Al alloy sheet in the engineering production, a corrosion potential gradient along the thickness of the Al alloy sheet was fabricated using the sprayed Zn layer. The process of arc spraying was employed to obtain the Zn coating with optimizing the parameters. Electrochemical testing was conducted on the surface of Al alloy sprayed with Zn layers at different depths. As the depth in the thickness direction increases, the content of Zn alloy elements gradually decreases and the potential gradually increases. This exhibits a gradual decrease in corrosion tendency. The results of electrochemical impedance spectra (EIS) revealed the existence of pitting corrosion on the surface of the Al alloy. This even extended to the underlying substrate material. In contrast, the Zn coating, when exposed to a corrosive environment, demonstrated the beneficial cathodic effect as a sacrificial anode and the protective function of a passivating film, thus mitigating corrosion. The gradual increase in charge transfer resistance in the impedance spectrum suggested that the corrosion resistance of the sample is increasingly improved. Therefore, it exhibited remarkable resistance to corrosion. Additionally, the SEM surface morphology and XRD pattern were utilized to further explain the corrosion mechanism of the arc-sprayed Zn coating. The Zn coating can provide sacrificial protection to the Al layer due to its higher negative potential and localized corrosion reactivity. This is attributed to the micro-galvanic couples formed between the Zn and Al layer, thus increasing the corrosion resistance of the sheets.

The microstructure and properties of copper coating fabricated by high velocity arc spraying

In this paper, the conductive copper coating on the surface of silicon nitride ceramics was fabricated by high velocity arc spraying with copper wires. The results indicate that copper coating with porosity less than 2.4 % was obtained, and a metallurgical bonding between the copper coating and the ceramic substrate. The copper coating presented a high microhardness of 303HV which surpassed the copper alloy and the thin film deposited by electrodeposition. Moreover, the copper coating exhibited a superior conductivity of 27.5 MS/m. Due to the rougher surface of the copper coating compared to copper sheet, a jagged intermetallic compound (IMC) layer was promoted during soldering process. It is feasible that an excellent conductive copper coating on the surface of ceramic substrate can be fabricated by high velocity arc spraying.

Surface modification of WE43 Mg alloy via combination of cold spray and micro-arc oxidation for wear related applications at high temperatures

This study investigates the high temperature wear behaviour of a WE43 Mg alloy after covering it with single and dual layer coatings. For this purpose, cold spray and micro-arc oxidation processes were employed individually and sequentially. Single-layer coatings fabricated by cold spray and micro-arc oxidation processes were Al/Al2O3 composite and MgO-based ceramic, respectively. Sequential application of cold spray and micro arc oxidation processes induced dual layer coating upon synthesizing an external Al2O3–based layer over the Al/Al2O3 composite layer. Results of the wear tests conducted under the load of 2 N revealed the superior resistance of the dual layer coated sample against the rubbing action of the counterface compared to single layer coatings. Thus, the presence of a relatively hard and tough external Al2O3-based layer over the Al/Al2O3 composite layer sustained protection up to the temperature of 320 °C, where the dominant wear mechanism was fatigue wear. However, the increase in the test temperature to 350 °C caused detachment of the external Al2O3-based layer. Reduction of the wear test load from 2 to 1 N resulted in the remaining of external Al2O3-based layer intact with the underlying Al/Al2O3 composite layer even at a test temperature of 350 °C. It is therefore concluded that the combination of cold spray and micro-arc oxidation processes is promising to broaden the reliable use of WE43 and other Mg alloys in wear related applications at high service temperatures.

Microstructure and wear behavior of WC-reinforced AlCoCrFeNiSi high entropy alloy coatings prepared by high-velocity arc spraying

In this study, AlCoCrFeNiSi/WC (WC from 0 to 40 wt%) high entropy alloys (HEAs) coatings were deposited on Q235 steel substrates using high-velocity arc spraying technique. The coatings' phases, microstructure, microhardness, nano-hardness, wear properties, and the mechanisms of wear were examined. The results have shown that the WC reinforced HEA had faced-centered cubic, body-centered cubic solid solution and carbide phases, while faced-centered cubic solution and Cr3Si, Al2O3 phase were observed in AlCoCrFeNiSi coating. The coatings possess a dense, lamellar structure and strong adhesion to the substrates. With the addition of reinforced particles, the porosity of the coatings initially decreases and then increases. The average microhardness of the coatings is significantly improved as WC content increased, reaching a maximum of 530 HV0.1. The ratio of nano-hardness to reduced elastic modulus rises as more WC is introduced. The coatings with the WC particles exhibit good wear resistance with the optimum wear rate at WC content of 40 wt%. Under the same conditions, the coating with 40 wt% of WC displayed the lowest wear rate, which decreased by 60.5 % compared to the AlCoCrFeNiSi coating. The AlCoCrFeNiSi coating experienced a mix of adhesive, abrasive, oxidative, and fatigue wear mechanisms. The wear mechanism changed to more abrasive, adhesive, and oxidative in the reinforced coatings. The load-bearing capacity and secondary phase strengthening effects of WC reduce the wear rate of the coatings.

Study on Initial Corrosion Behavior of Arc-thermally Spray Zn, Zn–Al, and Al–Mg Coatings Exposed in Atmospheric Environment for One-Year

This paper presents the results of a study comparing the initial corrosion characteristics of thermal spray coatings on Zn, Zn-Al, and Al–Mg thermal spray coatings after one year atmospheric exposure tests at two atmospheric environment sites. The thermal spray coatings were obtained by electroric arc spraying of various metals onto a carbon steel substrate. Atmospheric exposure tests were also conducted for outdoor accelerated exposure tests in which test specimens were applied with artificial seawater. The corrosion properties of these spray coatings were evaluated by surface analysis, film thickness measurements, cross-sectional analysis and anodic/cathodic polarization measurement. After one year of atmospheric exposure testing, white, granular corrosion products were observed on the surface of the Zn and Zn-Al thermal spray coatings, while no significant changes were observed in the Al–Mg thermal spray coating. Similar results were obtained for the surfaces of test specimens in atmospheric exposure tests with artificial seawater. The thickness of the thermal spray coating increased for the Zn thermal spray coating, while no significant change was observed for the other thermal spray coatings. Thus, differences in corrosion behavior were observed due to the composition of the thermal spray coatings. The initial corrosion behavior of the thermal spray coatings was also investigated based on the results of coating morphology and cross-sectional elemental distribution of the coatings.

Study on corrosion resistance of arc sprayed Zn–xAl (x = 19, 27, and 37) pseudo alloy coatings in salt spray environment

AbstractTo study the corrosion behavior of Zn–Al pseudo alloy coatings with different Al contents, Zn–xAl (x = 19, 27, and 37) pseudo alloy coatings were prepared by the wire arc spraying technique using Zn and Al wires with different diameters. This study investigated the microstructure, electrochemical corrosion behavior, and corrosion morphology and products of the as‐sprayed coatings after the salt spray test in 5 wt% NaCl solution. The results exhibited that the Zn–Al pseudo alloy coatings with higher Al content form denser corrosion products (Zn5(OH)8Cl2·H2O and Zn–Al layered double hydroxide) with stronger self‐shielding effect against corrosive media, thus provide better long‐term corrosion protection. Besides, electrochemical reactions are controlled by mass transfer until corrosion for 24 h, and then by a combination of mass transfer and diffusion for 96 h. Overall, it can be concluded that the Zn–37Al pseudo alloy coating in this study shows great potential to protect steel substrates from corrosion.

Influencing Factors and Process Optimization of Al/SiC Powder-cored Wires by Plasma Transferred Wire Arc Spraying

Influencing Factors and Process Optimization of Al/SiC Powder-cored Wires by Plasma Transferred Wire Arc Spraying

Research on Exposure to Salt Water Environment of Fe-based Amorphous Alloy Coating Fabricated by Twin Wire Arc Spray

Research on Exposure to Salt Water Environment of Fe-based Amorphous Alloy Coating Fabricated by Twin Wire Arc Spray

Effects of Al2O3 powder characteristics on microstructure, mechanical and tribological properties of Inconel 625-Al2O3 non-skid coatings prepared by plasma enhanced high-velocity arc spraying

The effects of the Al2O3 powder characteristics on the microstructure and properties of Inconel 625-Al2O3 non-skid coatings were investigated. The friction coefficient of the coatings increased with the size of the Al2O3 powder, which is beneficial for non-skid performance. However, the porosity and microdefects increased accordingly, degrading the mechanical properties and wear resistance. Among them, 25 wt% nano/micro Al2O3 powder is a better solution. m-Al2O3 with large size provided a high and stable friction coefficient, and the diffuse n-Al2O3 could repair and optimise the structural homogeneity. Meanwhile, n-Al2O3 enrichment areas on the wear scar result in excellent wear resistance. The in-flight sprayed particle size distribution could be adjusted by changing the Al2O3 powder particle size, enabling effective friction coefficient control.

INFLUENCE OF WIRE FEED RATE OF HIGH-SPEED ELECTRIC ARC METALLISATION ON STRUCTURE AND CORROSION PROPERTIES OF 30HGSA STEEL COATINGS

The study examines the porosity characteristics, corrosion analysis, and microstructure of iron-based coatings sprayed by supersonic arc metallisation in order to understand the regularity of the influence of the parameters by wire feed rate dependence. The performance of iron-based coatings depends on the integrity of the coating structure. Optimisation of arc spraying parameters allows minimising defects (pores, grain boundaries, unmelted particles, oxides and microcracks) that deteriorate coating properties. At high current levels, the microstructure of the coatings becomes more dense and the particle size decreases, also the average pore size decreases. As the wire feed rate increases, the value of current increases, which leads to the release of more heat energy at the arc to melt the wire and consequently favours the formation of dense coatings with low porosity.

Microstructure and properties of WC-reinforced AlCoCrFeNiSi high entropy alloy coatings prepared via high-velocity arc spraying

In this research, (AlCoCrFeNiSi)100-x(WC)x (x=0, 20 and 40 wt%) high entropy alloy (HEA) coatings were successfully deposited on the surface of Q235 steel substrate using high-velocity arc spraying method. The study investigated the presence of WC particles on the phase composition, microstructure, tensile bonding strength, and corrosion behavior of the HEA coatings. X-ray diffraction analysis revealed that without WC particles, the predominant phase in the coating was a face-centered cubic (FCC). However, when 20 wt% and 40 wt% of WC particles were added, the phase composition shifted to include FCC, body-centered cubic (BCC), W3C, Cr7C3, and other carbides. The WC particles also reduced the crystalline grain size of the coatings from 14.75 nm to 10.34 nm. The microhardness value increased from 252.5 HV0.1 to a peak of 529.9 HV0.1, as the content of WC increased representing a microhardness improvement factor ranging from 1.4 to 3 times that of the substrate. The tensile bonding strength of the coatings was also enhanced with WC content. The coating with 40 wt% WC particles demonstrated the highest tensile bonding strength of 40.23 MPa. The cohesion, adhesion, and glue failures occurred after the tensile test, with adhesion failure being more prominent in the coatings without WC particles and glue failure being more prominent in the WC-reinforced coatings. Compared to the Q235 steel substrate, the coated samples showed enhanced resistance against corrosion due to the formation of the passive oxide layers. The effective resistance against corrosion was attained when the proportion of WC particles was 20 wt%, displaying the least values for corrosion current density and corrosion rate in 3.5 wt% NaCl solution. Examination through SEM and XPS analysis indicated that the coatings’ structures and the formation of protective passive layers enhanced the corrosion resistance.

Microhardness and Elastic Properties Evaluation of WC-TiC Coatings Obtained by Arc Spraying Process

Fulfilling the basic role of hard thermal sprayied coatings is closely related to the value of its microhardness. The quality of such a layer depends on several variables, the main categories being: spray method (flame spray, electric arc, plasma spray, cold spray, etc.), spray parameters (spray distance, voltage and intensity, working atmosphere, direction of the spray jet, etc.) and the materials used (chemical composition of the coating materials, quality and texture of the substrate). In this study, the microhardness, elastic properties and cohesion of a coating made of hard cored wire (Praxair – Tafa) by electric arc spraying process on a low alloy steel substrate, were analyzed. The cored wire has as main hard elements WC (about 26%) and TiC (about 6%), the rest of the chemical elements present being: Cr (14%), Ni (4.5%), B (1.87%), Si (1.25%) and the Fe balance. The micro-hardness was evaluated onto the surface of the coating, previously prepared by grinding to reduce the as-coated roughness. The method based on recording the forcess generated during the indentation with simultaneous measurement of the load – depth curve (with UMT 2MCETR microtribometer) were used for the microhardness evaluation. In order to analyse the cohesion of the coated layer, scratch tests with progressive loading (10N, 15N and 20N) were performed on the same microtribometer. Tests have shown that the metal matrix uniformly includes the hard particles arised from the core of the wire, and at the microstructural level, the microhardness varies significantly, depending on the hardness of the particles on which the indentor tip applies the loading forces. However, the overall behavior of the coatings thus realized is a satisfactory one, being, as a general behavior, in the average required by the applications of such a layer.

Influence of factors of the electric arc spraying process on the properties of coatings

Influence of factors of the electric arc spraying process on the properties of coatings

Influence of Cu distribution in thermally sprayed Cu-bearing coatings on the prevention of Desulfovibrio vulgaris corrosion

Thermally sprayed Cu-based coatings show promise for combating microbiologically influenced corrosion (MIC) within natural gas pipelines. However, the efficacy of Cu-bearing coatings against MIC over prolonged exposure to bacterial fluids remains unclear. To examine the effect of Cu distribution on the prevention of MIC, two types of Cu-containing coatings were prepared: stainless steel (SS)-Cu composite coatings and Monel 400 coatings with Cu in solid solution. These coatings were deposited using high velocity oxy-fuel (HVOF) and wire arc spray (WAS) techniques. Dynamic flow corrosion testing was utilized to examine the influence of Cu concentration and distribution on biofilm attachment and pit formation. The results show that SS-Cu composite coatings exhibit preferential Cu dissolution when exposed to Desulfovibrio vulgaris solution, significantly reducing biofilm attachment over the short-term period (7 days) which correlated with the release rate of Cu ions. However, accelerated Cu ion release led to Cu2S deposition on sample surfaces, diminishing anti-biofilm properties with prolonged exposure (28 days). Pit depth measurements indicated a correlation between pit formation and Cu ion release throughout the exposure period, with bio-generic H2S likely contributing to increased pit corrosion. Utilizing the Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE), the anti-MIC performance of coatings were ranked based on biofilm thickness, biofilm coverage, pit depth, antimicrobial effect, and splat thickness. The ranking placed WAS Monel with Cu in solid solution as the most effective coating, attributed to its thin laminar structure, enhanced corrosion resistance, and antimicrobial properties. Cu in solid solution was concluded to be more effective in resisting MIC of Desulfovibrio vulgaris under dynamic flow conditions compared to Cu existing as segregated phase within composite coatings.

Influence of Post-Heat Treatment on the Characteristics of FeCrBMnSi Coating on Stainless Steel 304 Substrate Prepared by Twin Wire Arc Spray (TWAS) Method at Various Stand-off Distance

Influence of Post-Heat Treatment on the Characteristics of FeCrBMnSi Coating on Stainless Steel 304 Substrate Prepared by Twin Wire Arc Spray (TWAS) Method at Various Stand-off Distance