HVOF Spraying Research Articles

Excellent tribocorrosion resistance in artificial seawater of high entropy alloy FeCrNiCoAl coating prepared by HVOF

In marine environments, steel friction pairs undergo significant degradation due to the combined effects of wear and corrosion, known as tribocorrosion. This study investigates the tribocorrosion behavior and mechanisms under high loads of a High Entropy Alloy (HEA) FeCrNiCoAl coating applied by HVOF spraying, as well as cast ingot FeCrNiCoAl and 304SS samples, in artificial seawater. The investigations were conducted using electrochemical methods and in situ wear- electrochemical techniques. The tribocorrosion rate of the HVOF coating is approximately 1/5 that of the HEA cast ingot and 304SS samples. This is attributed to the coating's high hardness and the supporting and isolating effects of its oxide layers between splats. An intriguing finding is that the Open-Circuit Potential (OCP) trough value of the HVOF coating coincides with the peak Coefficient of Friction (COF) value during tribocorrosion in artificial seawater. This is due to the exposure of fresh surfaces following the local peeling off of flattened particles. Furthermore, the coating exhibits high re-passivation capabilities during wear because of high oxygen content in the coating. In comparison to corrosion, wear-induced material loss was identified as the primary contributor (≥ 99.8 %) to mass loss in both HEA cast ingot and coating samples. Optimizing the quantity and morphology of the HVOF coating has the potential to further enhance its tribocorrosion resistance. This study lays the foundation for developing advanced tribocorrosion-resistant coatings for use in seawater environments.

Research on microstructure, mechanical property and wear mechanism of AlCoCrFeNi/WC composite coating fabricated by HVOF

In this study, HVOF spraying technology was utilized to prepare AlCoCrFeNi/WC composite coatings with varying WC content on 40CrMnMoA steel substrate. The microstructure, elemental distribution, phase structure and chemical valence states of wear scratches of the composite coatings were analyzed using the SEM, EDS, XRD and XPS. Microhardness was measured using single-point digital microhardness tester, while nanohardness and elastic modulus were determined using a nano-indenter. The bonding strength of the composite coatings was evaluated using a tensile tester. Friction and wear tests were conducted to assess the wear behavior of the composite coatings. The results indicated that the microstructure, microhardness, nanohardness and elastic modulus of AlCoCrFeNi HEA coating increased with the addition of WC, attributed to the hard phase effects of WC. However, the bonding strength first decreased and then increased. Compared to the W 0 coating, the wear rates of the other composite coatings decreased by 30.5 %, 46.1 %, 65.3 %, and 82.1 %, respectively, which demonstrating that the effect strengthening of WC. After the friction and wear tests, the wear mechanism of the W 0 and W 1 coatings represents adhesive wear, abrasive wear and severe oxidation wear. In contrast, the W 2 and W 3 coatings exhibited slight adhesive wear, slight abrasive wear and slight oxidation wear, while the W 4 coating showed the slightest abrasive wear, the slightest adhesive wear and the slightest oxidation wear.

Thermally Sprayed Coatings for the Protection of Industrial Fan Blades.

This paper presents a study on thermally sprayed coatings. Coatings produced by high-velocity oxygen-fuel spraying HVOF and plasma spraying deposited on the A03590 aluminum casting alloy are tested. The subject of this research concerns coatings based on tungsten carbide WC, chromium carbide Cr3C2, composite coatings NiCrSiB + 2.5%Fe + 2.5%Cr, mixtures of tungsten and chromium powders WC-CrC-Ni, mixtures of carbide powders with the Cr3C2-NiCr + the composite 5% NiCrBSi and WC-Co + 5% NiCrBSi. The aim of this research is to find a coating most resistant to the erosive impact of particles contained in the medium centrifuged by industrial rotors. The suitability of the coating is determined by its high level of microhardness. The hardest coatings are selected from the coatings tested and subjected to abrasion tests against a sand particle impact jet and the centrifugation of a medium with corundum particles. It is found that the most favorable anti-erosion properties are demonstrated by a coating composed of a mixture of tungsten carbide and chromium carbide WC-CrC-Ni powders. It is concluded that the greatest resistance of this coating to the erosive impact of the particle jet results from the synergistic enhancement of the most favorable features of both cermets.

Enhancing Wear Resistance of Marine Steel with Fe Based Amorphous Coating Via HVOF Spraying

Mechanical friction in marine environments poses significant challenges, leading to resource depletion and energy consumption. Tribocorrosion, combining electrochemical corrosion and friction wear, jeopardizes metal components, necessitating robust protective measures. Despite minimal wear of marine equipment, even slight mass reductions can trigger catastrophic failures, resulting in substantial maintenance expenses. Steel structures in marine settings are vulnerable to corrosion from aggressive external and internal factors. ASTM AH36 steel, widely used in marine construction, faces wear challenges despite corrosion resistance, prompting the need for surface treatments and coatings to enhance longevity. Previous research emphasizes thermal spray methods, particularly HVOF-applied coatings, as eco-friendly solutions for improving wear resistance on marine steels. Fe-based coatings, characterized by improved hardness and corrosion resistance, offer promising solutions in abrasive marine environments, igniting fervent research efforts. This study conclusively demonstrates that AH36 steel samples coated with Fe-based amorphous layers exhibit substantially reduced wear rates.

Study on Combustion Characteristics and Flame Flow Behavior with Ethanol-Kerosene Mixed Fuel in HVOF Spraying

Study on Combustion Characteristics and Flame Flow Behavior with Ethanol-Kerosene Mixed Fuel in HVOF Spraying

Artificial Neural Networks in Spray Coatings for Protection of Hydroturbines in Silt Conditions

Background: Artificial intelligence techniques are able to predict the erosion in various coatings. In recent times, the erosion of the coating was successfully predicted using artificial neural networks (ANN). Aim: This patent aims to present the critical findings in the area of spray coatings used for the protection of hydroturbines. This critical review explores the surface erosion of numerous hydroturbine materials and coatings. Moreover, it covers the evolution of coating techniques used in different industries such as hydropower plants and materials handling industry. Objective: The objective of this patent is to present the critical finding in the field of erosion wear in coatings utilizing an artificial neural networks (ANN) technique. Methods: The effect of influencing factors on silt erosion was assessed. However, the evolution of various coating processes was explored comprehensively. Furthermore, the properties of various coatings, namely WC, Cr2C3, and Ni/Co coatings, were reported. A number of comparative analyses were carried out that can help in the selection of coatings on the basis of their mechanical as well as chemical properties. The applications of ANN in the spray industry were explained extensively. Results: The results show that the HVOF coating is the most widely used deposition method. HVOF is an appropriate technique for both ceramics and pure metals. Ceramics, as well as cermet, are deposited to enhance the wear and tear resistance of hydroturbine materials. As a result, the HVOF, laser cladding, D-Gun, and plasma spray technique are optimal in these circumstances. Coatings based on WC have been employed by several researchers to increase stainless steels' resistance to erosion and wear. Conclusion: With the application of appropriate models and ML methods, it is expected that coatings with specific desired properties can be manufactured with fewer experiments. There is no surprise that WC-10Co-4Cr finds widespread usage in a variety of industrial contexts. Ni- and Cobased coatings show promise for use in tribological settings. Stellite is suggested by several researchers for high-erosion duty conditions in hydroturbines. Co-based coatings are more erosion resistant as compared to No-based coatings. Coatings formulated with chromium (Cr) are resistant to erosion and wear in harsh mining environments.

Study of Turbulent Behavior and Particle Flight Characteristics Based on Different Turbulence Models During HVOF Spraying

Study of Turbulent Behavior and Particle Flight Characteristics Based on Different Turbulence Models During HVOF Spraying

Effect of heat treatment on microstructure and cavitation resistance of multi-dimensional WC-10Co4Cr coating

The multi-dimensional WC-10Co4Cr coating was prepared on 316 stainless steel by using HVOF spraying, and the impact of heat treatment temperature on the microstructure, cavitation resistance, and mechanical properties of the multi-dimensional WC-10Co4Cr coating was studied. Heat treatment at higher temperatures leads to lower porosity and upper hardness of the coating. Meanwhile, oxidation products such as CoWO4 and Cr2O3 were produced at 500°C. The coating has the best anti-cavitation performance after heat treatment at 300°C.

The Effect of HVOF Spray Distance on Solid Particle Erosion Resistance of WC-based Cermets Bonded by Co, Co-Cr and Ni Deposited on Mg-alloy Substrate

The Effect of HVOF Spray Distance on Solid Particle Erosion Resistance of WC-based Cermets Bonded by Co, Co-Cr and Ni Deposited on Mg-alloy Substrate

Characteristic Analysis and Coating Application of the Innovative HVOF System Based on the Digital Model

In view of the poor working conditions, high cost and time-consuming parameter design of the traditional spray process, an innovative HVOF thermal spray system based on the digital model has been established by this study to improve coating performance and optimize scheme design rapidly. In particular, the digital model of the oxygen/kerosene HVOF spray system is designed on the AMESim multidisciplinary simulation platform for the first time, and the engineering prototype has been successfully developed. Thus, an efficient design method based on the digital model was proposed, according to which the spray control parameters such as oxygen and kerosene flow are obtained conveniently under a combustion chamber pressure of 1.0 MPa and 2.0 MPa, respectively. The error between the simulation and experiment results was generally less than 5%, and the dynamic characteristics of the key components in the actual spray system were well predicted, suggesting that the dynamic response time of the system would generally less than 0.7 s. Additionally, the WC-12Co coatings were deposited under the working conditions of W1.0 and W2.0, respectively, the microhardness of the coating increased about 23% and the corresponding volume wear rate decreased about 18%. The results show that the increase of the pressure of the combustion chamber can further improve the coating performance, which also verifies the feasibility and reliability of the design method. It was concluded that the innovative HVOF system based on the digital model is of great theoretical value and application significance for predicting spray process parameters conveniently and providing excellent coating performance.

Parametric optimization corrosion erosive wear and XPS response of FeCrCoAlTiB and FeCrCoNiSiB coatings on Q235 steel substrate by HVOF spraying using taguchi method

In the study high-velocity oxy-fuel thermal spraying to create Fe32Cr21Co21Al16Ti5B5 and Fe43Cr16Co12Al14Ti5B10, Fe32Cr21Co21Ni16Si5B5 and Fe43Cr16Co12Ni14Si5B10 coatings on Q235 steel substrates. Jet-type testing is used to examine the coatings’ resistance to slurry wear. Researchers examined the surface to learn more about the erosion process. Taguchi analysis and a wear model confirm the significance of the selected important factors. The wear model’s proposed mechanism shows remarkable agreement with the data. Coating loss may be attributed to several causes, including mixed ploughing, and cutting, platelet development, abrasion grooves, and cracking. The outcomes showed that the effect speed was the main contributing variable, the contribution ratio reached 65% to 70%, for the impact velocity of coating no 1 to 4. In contrast, it is recognized that impact velocity > impingement angle > erodent feed rate > erodent size is the most important sequence. Micro-cutting, mixed cutting, and ploughing were the essential disintegration systems for all coatings at low impingement points. In contrast, platelets were detected under normal impingement angles, as confirmed by SEM analysis. Both coatings seem to form passivation films, as shown by their greater Ecorr values relative to the substrate. Fe, Co, Cr, Al, and O all show up as peaks in XPS analyses.

Influence of HVOF spraying parameters on microstructure and mechanical properties of FeCrMnCoNi high-entropy coatings (HECs)

Influence of HVOF spraying parameters on microstructure and mechanical properties of FeCrMnCoNi high-entropy coatings (HECs)

High Temperature Corrosion in Water Vapor of Fe–2.25Cr–0.54Mo Coated with Ni-Based Alloy Containing WC–Co Using an HVOF Spraying Technique

High Temperature Corrosion in Water Vapor of Fe–2.25Cr–0.54Mo Coated with Ni-Based Alloy Containing WC–Co Using an HVOF Spraying Technique

SPRAYING PROCESS FOR Cr<sub>3</sub>C<sub>2</sub>-NiCr COATING

In this paper, the theoretical research of Cr3C2-NiCr coating for zirconia substrate is discussed. To obtain this coating, one of the multi-efficiency methods high velocity oxygen-fuel thermal spraying (HVOF) was investigated. The coatings were processed by different thicknesses of zirconia substrate sample of 3–5 mm also with length of 20 mm and width of 30 mm, at spraying speed of 600–700 m/s. The temperature during HVOF spraying is about 3000 ºC and the cooling temperature is 27 ºC. Investigating the theoretical data of Cr3C2-NiCr coatings, the development and thermal stresses after HVOF treatment were determined using Stone's method and Brenner-Senderoff equations with a coating thickness not exceeding 0.6 mm for carbide coatings. According to the results of theoretical research, the deposition efficiency values were found by the method proposed by Kosaku Shinoda. According to the theoretical and mathematical calculations, the deposition efficiency for Cr3C2-NiCr coating with zirconia substrate is in the range of 59.5%–69.4%. Thus, it was found that the deposition efficiency for the coatings depends on the thickness of the substrate, the powder feed rate, and the mass of the applied material and consequently the number of spraying passes.

Effect of 3.5 % NaCl solution with different Na2S concentrations on ultrasonic cavitation erosion behaviors of HVOF sprayed WC-Ni coatings

In this article, the WC-10Ni coatings were fabricated by HVOF spray, then the ultrasonic cavitation erosion performances of the coatings in distilled water and 3.5 wt% NaCl solution with various Na2S concentrations (0, 20 and 200 ppm) were investigated. The results of the cumulative volume loss of the coating in different mediums showed that the coating exhibited enhanced cavitation erosion resistance with the increase of Na2S concentrations in medium. The reason for the improvement on the cavitation erosion performance was the growth of corrosion product films containing sulphide. In comparison with the coating after cavitation erosion in medium without Na2S, no large craters and deep grooves were observed on the eroded coating surface in medium with Na2S. The ultrasonic cavitation damage of the coating manifests as the spall of the metal binder phase (Ni) and exposure of the hard phase (WC).

HVOF Spray Performance Optimization Analysis and Experimental Research of WC–12Co Coating on Ti Alloy

HVOF Spray Performance Optimization Analysis and Experimental Research of WC–12Co Coating on Ti Alloy

Effect of Cr3C2 content on microstructure, mechanical and tribological properties of Ni3Al-based coatings

To broaden the applicability of Cr3C2 -reinforced Ni3Al-based coatings, which possess exceptional high-temperature strength and anti-friction properties for high-temperature solid lubrication, this study examined the influence of varying Cr3C2 concentrations (0 wt%, 10 wt%, 15 wt%, and 20 wt%) on the phase composition, microstructure, mechanical performance, and friction and wear behaviors of Ni3Al-based coatings from 25 °C to 800 °C. The findings indicated that decarburization of Cr3C2 took place during HVOF spraying, forming Cr7C3. The remarkable high-temperature lubricity of all coatings can be attributed to the synergistic lubrication effect resulting from the precipitation of soft metal Ag, the brittle-plastic transformation of MoO3, and high-temperature solid lubricants such as NiCr2O4 and Ag2MoO4, which are induced by high-temperature friction. The second phase strengthening of Cr3C2 and the solute effect in the Ni3Al matrix phase significantly improved the hardness and toughness of the coatings, thereby enhancing their wear resistance. Notably, the coating containing 15 wt% Cr3C2 exhibited the lowest coefficients of friction (COFs) and wear rates (WRs) (10−5 mm3·(N·m)−1), ranging from 0.60 to 0.26 and 14.48 to 2.01 at 25 °C to 800 °C, which can be ascribed to the coordination between lubricity and mechanical strength.

Tribological Properties and Corrosion Resistance of Stellite 20 Alloy Coating Prepared by HVOF and HVAF

This study examines the tribological and corrosion properties of Stellite 20 alloy coatings on F310H heat-resistant stainless steel that were prepared using HVOF and HVAF supersonic flame spraying techniques. To investigate the coatings’ microstructure, phase, microhardness, wear, and corrosion resistance, a range of characterization techniques, including SEM, EDS, XRD, microhardness, and friction wear-testers, weas employed. The results indicate that both HVOF and HVAF-prepared coatings exhibit a dense structure with porosity of 0.41% and 0.32%, respectively. The coatings are composed of γ-Co solid solution, ε-Co solid solution, Cr-rich solid solution, Cr7C3, WC, and CoCr2O4 phases. The microhardness of the Stellite 20 coatings prepared by HVOF and HVAF methods was 610 HV0.3 and 690 HV0.3, respectively, which is three times higher than that of the F310H stainless steel substrate. The wear mechanism of the HVAF coating is abrasive wear, while the wear mechanism of the HVOF coating is mainly fatigue wear with slight abrasive wear. The HVAF coating demonstrates superior wear resistance due to its higher flame velocity, denser coating, and higher average microhardness. In contrast, the HVOF coating shows a higher friction coefficient stability due to its lower hardness dispersion. The corrosion potentials of the HVOF and HVAF coatings are −0.532 V and −0.376 V, respectively, with corresponding corrosion current densities of 1.692 × 10−7 A·cm−2 and 6.268 × 10−7 A·cm−2, respectively. Compared to the HVOF coating, the Stellite 20 coating prepared using HVAF technology exhibits better wear and corrosion resistance.

Properties of Al-Based Amorphous Coatings Prepared by Low-temperature HVOF Spraying

Properties of Al-Based Amorphous Coatings Prepared by Low-temperature HVOF Spraying

Corrosion and wear of coatings fabricated by HVOF-spraying of nanostructured and conventional WC–10Co-4Cr powders on Al7075-T6

The present work compares WC-10Co-4Cr coatings fabricated by HVOF spraying of a conventional powder (1.33 ± 0.67 μm) and a nanostructured powder (0.17 ± 0.06 μm) on Al7075-T6, in terms of microstructure and phase composition, microhardness and fracture toughness, corrosion performance in 3.5 wt% NaCl (potentiodynamic polarization, chronoamperometry, galvanic effect measurements and salt spraying) and sliding wear performance under lubrication. Τhe nanocoating, despite its greater microporosity and decarburization, displayed higher microhardness, fracture toughness and surface roughness compared to its conventional counterpart. A superiority of the corrosion behaviour and sliding wear behaviour of the nanocoating as compared to its conventional analogue was observed in terms of a higher resistance to general/localized corrosion, lower passive film conductivity, lower wear rate, subtler wear scars and greater occurrence of islands of tribofilms. The reasons for such superiority are being clarified. A good galvanic compatibility between the nanocoating and its substrate was manifested. Both coatings exhibited high corrosion resistance during salt spraying for 45 days. The mechanisms of corrosion and wear degradation are being proposed.