High-velocity Oxygen-fuel Spraying Research Articles

Comparative Study on the Microstructure and Properties of 304 Stainless Steel Coatings Prepared by High-Velocity Oxygen Fuel Spraying and Air Plasma Spraying

Comparative Study on the Microstructure and Properties of 304 Stainless Steel Coatings Prepared by High-Velocity Oxygen Fuel Spraying and Air Plasma Spraying

Influence of temperature on the nanomechanical characteristics and wear performance of FeCrMoNiBCuSiC coating

This paper introduced a metallic glass coating, Fe50.5Cr20Mo15Ni5B4.5Cu2.5Si1.8C0.6 (wt%), deposited via high velocity oxygen-fuel (HVOF) spraying. The phase composition, thermodynamic stability, microstructure, nanomechanical characteristics, and wear performance at different temperatures were investigated. The coating exhibited an amorphous/nanocrystalline structure and a crystallization temperature of 632 ℃. The hardness and creep displacements were (11.01 ± 1.24) GPa and 23 nm, respectively. After annealing at 300 ℃ and 600 ℃, the corresponding hardness increased to (15.12 ± 1.20) GPa and (17.24 ± 1.49) GPa, while the creep displacements decreased to 7 nm and 5 nm. The wear rate showed a positive correlation with temperature (T1/2), while the friction coefficient displayed a negative correlation. This study provided new insights into the elevated-temperature wear characteristics of Fe-based metallic glass coatings.

Corrosion behavior of HVOF sprayed 304 stainless steel coating on 6061 substrate in 3.5 wt% NaCl solution

This study aimed to improve the corrosion resistance of lightweight material surfaces by applying a 304 stainless steel coating (304SSC) onto 6061 aluminum alloy using high-velocity oxygen-fuel (HVOF) spraying. The phase composition, microhardness, microstructure, and long-term corrosion behavior of the HVOF-sprayed 304SSC in 3.5 wt% NaCl solutions were analyzed through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and an automated micro-hardness testing system. The findings indicated that the corrosion resistance of the coatings improved as the number of deposited layers increased. Moreover, the coatings that displayed the highest resistance to chloride ion attack in long-term immersion experiments also effectively prevented galvanic coupling. The enhanced corrosion resistance was attributed to reduced porosity, increased densification, and enhanced mechanical stability of the coatings.

Tribological performance of c-BN/TiC-enhanced NiCrBSi coatings prepared by high-velocity oxy-fuel spraying tested from room temperature to 1000 °C

The c-BN/TiC-enhanced NiCrBSi composite powder and coatings were prepared by spray-drying and high-velocity oxygen-fuel (HVOF) spraying, respectively. The phases, microstructures and tribological performance were studied from room temperature to 1000 °C, and the wear mechanisms of coatings were analyzed and discussed. The results showed that TiC and c-BN distributed evenly in NiCrBSi phase, but with the increase of temperature, c-BN showed a certain degree of aggregation, while TiC particles grew significantly. Therefore, the coating shows good wear resistance at room temperature. As the temperature increased, the wear rate of the coating increased, and the wear resistance decreased, so the maximum wear rate was obtained at 800 °C. However, when the temperature was increased to 1000 °C, a composite enamel layer of oxide and hard phase was generated on the surface of the abrasion marks, which improved the wear resistance of the coating, significantly reducing the wear rate.

Effect of HVOF spray coating on the tribological surface of onshore gate valves

Gate valve is one of the most common design concepts in onshore Oil & Gas installations. This equipment is composed of a wedge-shaped obturator that performs linear sliding movements during activation. Fluid sealing is achieved through metallic contact between the surfaces of the gate and seat components. Metal surfaces are commonly hardened by heat treatment or coated with Stellite 6 alloy by plasma-transferred arc welding (PTAW). The application of high-velocity oxygen fuel (HVOF) coatings on these surfaces for wedge-gate valves has not yet been foreseen. In addition, comparative studies on the tribological performance of technical surfaces used in onshore wedge-gate valves are also scarce. Therefore, this study presents the results of tests performed on specimens using a ball-on-flat tribometer with linear reciprocating sliding, simulating a gate valve tribosystem in operation: flat (gate) and ball (seat). Martensitic stainless steel 13Cr was used with the contact interfaces under the following conditions: (A) heat treated, (B) Stellite 6 coating by PTAW, (C) Stellite 6 coating by HVOF, and (D) tungsten carbide coating by HVOF. The flat/ball tribological pairs investigated were A/B (TRIM 8), B/B (TRIM 5), C/B, and D/B. The coefficient of friction (COF), surface wear, and wear mechanisms were comparatively evaluated. The results showed that the newly proposed surfaces (C and D) are promising alternatives to reduce material consumption and improve the performance of valves in operation according to the application requirements.

The effect of WC-12Co and CrC-NiCr hard coatings applied by HVOF method on the microstructure, mechanical, and surface properties of steel

In today’s world, the use of metals is widespread across various industries, with St37 steel plying a significant role. However, over time, this metal undergoes significant deterioration in its mechanical and physical properties, mainly due to factors such as corrosion and wear. Rather than using expensive methods such as alloying to extend the life of the metal, a more economical and practical approach is to focus on improving the surface properties. Surface engineering techniques, particularly thermal spraying, offer a viable solution. Among thermal spray techniques, High Velocity Oxygen Fuel (HVOF) spraying stands out as an economical and time-saving method for producing materials, equipment or machine components with high resistance to damage mechanisms such as corrosion, erosion and wear. This study investigates the application of tungsten carbide and chromium carbide-nickel chromium coatings to St37 steel surfaces using the HVOF method. Microhardness measurements were carried out after coating to evaluate the mechanical properties, while scratch and wear tests were carried out to determine the tribological properties. In addition, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to assess the structural characteristics of the samples. The results indicate the formation of phases such as Cr3C2, NiCr and W2C on the low-alloy steel surface after the tungsten carbide and chromium carbide-nickel-chromium coating processes. Coating thicknesses of 204 and 239 µm were achieved for tungsten carbide and chromium carbide-nickel-chromium, respectively. These coatings contributed to improved mechanical and tribological properties. The WC-12Co coated sample exhibited the highest hardness value (1304 HV0.1), while the CrC-NiCr coated sample recorded the highest critical load value in the scratch test (48 N). The WC-12Co coated samples showed the best wear resistance.

Optimization of High-Velocity Oxygen Fuel Spray Process Parameters to Achieve Maximum Thickness and Minimum Porosity in Vanadium Carbide Coating

Optimization of High-Velocity Oxygen Fuel Spray Process Parameters to Achieve Maximum Thickness and Minimum Porosity in Vanadium Carbide Coating

Novel candidate of metal-based thermal barrier coatings: High-entropy alloy

To obtain compatible properties of low thermal conductivity and high thermal stability, Al0.6CoCrFeNiTi high-entropy alloy was designed as a novel candidate of metal-based thermal barrier coatings (MBTBCs). The corresponding high-entropy alloy coatings were fabricated by both high-velocity oxygen-fuel spraying (HVOF) and atmospheric plasma spraying (APS), and then the dependence of thermal insulation properties on microstructure was investigated. The both coatings exhibit a simple body-centered cubic (BCC) structure, but present obvious difference in microstructure and defect characters which relates to the evolution of in-flight particles. Benefit from the extremely low thermal conductivity, the APS-deposited coating can increase 13.24 °C of the surface temperature of piston crown and yield a temperature reduction of 19.00 °C along the thickness direction, which mean a positivity on enhancing the power efficiency of vehicle engines without sacrificing the strength of aluminum alloy components. In virtue of a decoupling method, the crucial effect of microstructure on thermal conductivity is disclosed, thus interpreting the excellent thermal insulation property of APS-deposited coating dominated by grain refinement and disordered BCC structure. The present results demonstrate a great potential of high-entropy alloy coatings as thermal barrier application and provide an inspiration for future works aiming to design these coatings to meet specific engineering needs.

Improved tribological and electrochemical behavior of concentrated chromite coatings developed by HVOF and plasma spray techniques

Mineral coatings have the ability to tackle the most common degradation processes (wear and corrosion) in industries at amazing ‘quality to cost’ ratio, as compared to synthetic ceramics. In the current study, concentrated natural chromite with 55 wt.% Chromium oxide (Cr2O3) is deposited on steel substrate through High Velocity Oxygen Fuel (HVOF) and Atmospheric plasma spray (APS) techniques. Effect of deposition processes and Cr2O3 enrichment on microstructure, hardness, tribological and electrochemical behavior of coatings is studied. Tribological tests were performed using pin-on-disc setup, coatings deposited with APS have shown excellent wear resistance behavior as compared to HVOF coating. Owing to the brittle nature of chromite coatings, they were worn by abrasive wear irrespective of the deposition process. Electrochemical behavior of coatings is evaluated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. APS and HVOF coatings have exhibited very high protective efficiency of 93 and 88% respectively, against steel substrate. Equivalent electrical circuit (EEC) based on EIS results has also been conceptualized and verified with ZSimpWin analysis software. Established EEC has illustrated capacitive behavior due to the protective oxide nature of coatings. Despite having relatively higher porosities in APS coatings, they display an excellent potential for wear and corrosion resistant applications. Results revealed that hardness, compactness, tribological and corrosion performance of chromite coatings have been substantially improved due to higher Cr2O3 content.

Effect of binder phases on the cavitation erosion behavior of HVOF sprayed WC-based coatings

In order to address the issue of cavitation erosion (CE) damage in marine mechanical components, WC-10Co4Cr (WCC), WC-10Co (WC1) and WC-17Co (WC2) coatings were prepared on the surface of 316L stainless steel using high-velocity oxygen-fuel (HVOF) spraying technique. The study investigated the microstructures, phases, mechanical properties and CE behavior of the coatings with different binder phases. The effects of the type and content of binder phase on the CE resistance and mechanism of the coatings were studied by compared the differences of volume loss rate (VLR) and eroded surface morphologies between the coatings. It was observed that all three coatings were dense and tightly bonded to the substrate. The primary phases identified in the coatings were WC, W2C and Co3W3C. Compared with the WC1 and WC2 coatings, the WCC coating demonstrated superior CE resistance with the lowest volume loss rate (VLR). The VLR of the WC1 and WC2 coatings was approximately four times higher than that of the WCC coating. The binder phase of Co-Cr improved the mechanical properties and the bonding strength of hard and binder phase, which reduces the brittle detachment of WC particles. In addition, the WCC coating had high microhardness and elastic modulus (E), H/E and H3/E2, which hindered the initiation and propagation of fatigue cracks. The initiation of CE damage occurred at the original defects, such as pores, cracks. The primary CE mechanism of the coatings was the interlinking of cavitation craters, lamellar spalling caused by the fatigue cracks propagation along the interlayer. The brittle detachment of WC hard particles also occurred significantly in WC1 and WC2 coatings due to loss of the binder phase. It was concluded that the binder phase markedly influenced the CE resistance and mechanism of the coatings, the addition of Cr showed the most pronounced effect.

Microstructure and tribological properties of ZrB2-enhanced NiCrBSi coatings prepared by high-velocity oxy-fuel spraying

This paper presented a novel study of the preparation of ZrB2-enhanced NiCrBSi coatings and its microstructure and tribological properties. NiCrBSi-ZrB2 composite powder and coatings with ZrB2 contents of 20 %, 40 %, and 50 % were prepared by spray-drying and high-velocity oxygen-fuel (HVOF) spraying, respectively. The microstructure and high-temperature wear performance at 700 °C were compared with those of an NiCrBSi coating. The results showed that the NiCrBSi and ZrB2 powder exhibited good wetting properties in the solid-liquid sintering zone and the CrB phase was formed in the liquid phase contact zone in composite coatings with ZrB2 contents of 20 % and 40 %, while the CrB phase disappeared in the 50 %ZrB2 coating due to the pinning effect caused by excessive ZrB2. The microhardness of composite coatings tended to increase, then decrease, and the 40%ZrB2 coating reached a maximum hardness of 874 HV. The NiCrBSi coating presented oxidative wear and adhesive wear. Although the fracture toughness of composite coatings was lower than that of the NiCrBSi coating, the wear resistance in the composite coating was significantly enhanced due to the evenly distributed ZrB2 and CrB phases. The 20%ZrB2 coating with low fracture toughness and the 50 %ZrB2 coating with hardness mismatch caused by the absence of CrB produced severe abrasive wear. The hardness gradient with the matrix, ZrB2 and CrB phases reduced abrasive wear caused by peeling in 40%ZrB2 coating, and the ceramic phases acted as skeletons reducing the deformation of the load contact area. The formation of Cr2O3 during the friction process further improved the wear resistance. The wear mechanism of 40%ZrB2 coating underwent light adhesive wear, mild abrasive wear and oxidative wear, and the coating exhibited the best wear resistance with the lowest wear rate of 1.16 × 10−13 m3/N·m (a decreased of 56 %).

Development and Research of New Hybrid Composites in Order to Increase Reliability and Durability of Structural Elements

Hybrid composite materials can successfully solve the problems of reliability, durability, and extended functionality of products, components, and details, which operate under conditions of multifactorial influences (temperature, force, and deformation). The authors have developed a hybrid composite high-entropy AlCoCrCuFeNi material and ceramic cBNCoMo(B4CCoMo) layer. The formation of hybrid composites was carried out using new technology. This technology includes high-energy machining, high-velocity oxygen-fuel spraying in a protective environment, high-temperature thermomechanical treatment, and heat treatment. The use of the developed technology made it possible to increase the adhesive strength of the composite layers from 68 to 192 MPa. The authors performed an assessment of the structural parameters of the composite layers. The assessment showed that the composite layers had a nanocrystalline structure. The research included mechanical tests of the hybrid composites Hastelloy X (NiCrFeMo)—AlCoCrCuFeNi—cBNCoMo and Hastelloy X (NiCrFeMo)—AlCoCrCuFeNi—B4CCoMo for cyclic durability (fatigue mechanical tests) and friction wear. The use of surface-layered materials AlCoCrCuFeNi—cBNCoMo and AlCoCrCuFeNi—B4CCoMo in the composition of hybrid composites significantly increased cyclic durability. The use of surface-layered materials in the composition of hybrid composites made it possible to reduce wear intensity. The test results show that the developed composites are promising for use in various industries (including oil and gas), where high strength and wear resistance of materials are required.

The coupling effect of cavitation-erosion and corrosion for HVOF sprayed Cu-based medium-entropy alloy coating in 3.5 wt.% NaCl solution

Ship propellers suffered from serious coupling damage of cavitation-erosion (CE) and corrosion when operated with high-speed in the marine environment. To improve the CE-corrosion resistance of the Ni–Al bronze (NAB) propeller alloy, a novel Cu-based medium-entropy alloy coating (Cu55Al20Ni12Ti8Si5, at.%) was prepared by high-velocity oxygen-fuel spraying technology in this study. The characteristics and CE behavior of coating and NAB were comparatively investigated, then the CE damage mechanism was discussed by analyzing CE damage morphologies. The influence of CE on corrosion behavior and the coupling effect between CE and corrosion were further elucidated by electrochemical corrosion experiments. The results indicated that the as-sprayed coating mainly comprised of BCC solid solution phase and NiTi-rich precipitates, which possessed higher hardness (6.73 ± 1.23 GPa) and superior resilience (27.0%) than the NAB. The cumulative mass loss rate for the coating after 18 h CE in distilled water and 3.5 wt.% NaCl solution was only 38.7% and 80.6% that for the NAB, revealing the better anti-CE performance of the coating. The preferential CE of the BCC matrix around the NiTi-rich precipitates, fatigue fracture and lamellar spalling were summarized as the main CE damage mechanism for the coating in 3.5 wt.% NaCl solution. CE had a significant influence on corrosion behavior of coating and NAB, which resulted in corrosion performance degradation of both two materials. The CE-corrosion coupling effect led to the remarkable mass loss, and mechanical effect rather than corrosion effect was ascribed to be the dominated factor for the damage of coating and NAB.

Evaluation of corrosion and wear performance of Fe-based coating and hastelloy C276 in H2S environment on 304 stainless steel substrate

In order to improve the performance of 304 stainless steel for use in oil and gas field applications and broaden its applicability, Fe-based coatings with small amounts of amorphous structures were prepared by high-velocity oxygen-fuel spraying onto stainless steel substrates. The wear resistance and hydrogen sulfide corrosion resistance of the coatings were tested and compared to the preferred corrosion resistance of Hastelloy C276 coatings. Samples with two kinds of coatings were subjected to 720 h of corrosion in a 40 °C H2S solution. The effects of corrosion on the microstructure and phase composition of the sprayed coatings were analyzed using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The mechanical properties of the materials were characterized using nano-indentation, a friction-abrasion testing machine, and confocal laser microscopy. The results showed that both coatings provided excellent resistance to H2S corrosion (0.14, 0.15 mm/y), but the Fe-based coating was more effective at enhancing the hardness (twice as much as C276 coating), Young's modulus, and wear resistance of the stainless steel. Given its higher wear resistance and lower cost, the Fe-based coating was concluded to be more effective in protecting 304 stainless steel for use in oil and gas applications.

Effect of High-Energy Shot Peening on Properties of High-Velocity Oxygen-Fuel Spraying

A Cr3C2-Al2O3-NiCr composite coating was prepared on an INCONEL600 alloy surface through high-velocity oxygen-fuel spraying followed by further processing through high-energy shot peening to create the composite coating. The microhardness and friction properties of the composite coating are analyzed by a microhardness tester and reciprocating friction tester. The microscopic structure and wear trace of the composite coating were analyzed by scanning electron microscope (SEM). The element distribution of the coating was analyzed by energy-dispersive spectroscopy (EDS). The porosity of the coating was detected by industrial CT. The phase and residual stress of the coating were tested by X-ray diffraction (XRD). The electrochemical corrosion and friction wear performance of the samples under different surface states were discussed. The results showed that the compactness of the coating was improved and the porosity was significantly reduced after high-energy shot peening. The high-energy shot peening did not alter the phase composition of the coating but introduced residual compressive stress. The microhardness of theCr3C2-Al2O3-NiCr high-velocity oxygen-fuel coating can reach 2.9 times that of the INCONEL600 substrate, and the hardness of the coating after high-energy shot peening can reach 3.9 times of that of the substrate. After high-energy shot peening, the corrosion resistance of the coating in HCl solution is improved. Compared with the INCONEL600 substrate, the friction coefficient and calculated wear rate of the Cr3C2-Al2O3-NiCr high-velocity oxygen-fuel coating decrease by 62.5% and 79.6%, respectively. After high-energy shot peening, the friction coefficient and calculated wear rate of the coating decrease by 75% and 98.7%, respectively.

Cavitation-silt erosion behavior and mechanism in simulated sea water slurries of cermet coatings manufactured by HVOF spraying

Understanding the interaction between the sea water slurries and flow-handling components is important for enhancing the cavitation-silt erosion (CSE) resistance of the ocean power generation systems. In this manuscript, two cermet coatings (i.e., Cr3C2-25(NiCr) coating and WC-10(Ni) coating) were manufactured via a high-velocity oxygen fuel (HVOF) spraying method, and influences of sand concentrations (SCs) as well as flow velocities (FVs) on their CSE characteristics in simulated sea water slurries (SSWS) were investigated. Results indicated that the Cr3C2-25(NiCr) coating exhibited larger porosity, lower hardness (H) and elastic modulus (E), stronger ability to resist corrosion in 3.5 wt.% saline solution as well as worse CSE resistance in SSWS, and its CSE resistance was more affected by both the SC and FV by comparison to the WC-10(Ni) coating. Both SC and FV had a positive effect on the CSE damage for the Cr3C2-25(NiCr) and WC-10(Ni) coatings, while SC had more influence on their CSE resistances than FV. The CSE deterioration mechanisms in SSWS under different SCs and FVs of the Cr3C2-25(NiCr) and WC-10(Ni) coatings were also compared and revealed.

APPLICATION OF HVOF TECHNOLOGY FOR WC-BASED WEAR-RESISTANT COATINGS – AN OVERVIEW

The article presents the main problems of wear and service life of slide gate valves for trunk pipeline transport of oil and gas industry. One of the possible ways to solve these problems is the application of a thin layer of wear-resistant and corrosion-resistant coatings. Due to the ever-increasing cost of materials, as well as the increased requirements for materials, coating methods have recently become increasingly important. Among the gas-thermal coating methods, the High Velocity Oxygen-Fuel Spray (HVOF) technology is a new and rapidly developing technology that produces high density coatings with porosity less than 1%, with improved hardness and adhesion as well as improved erosion, corrosion and wear resistance properties. This overview article provides a comparative review of the characteristics of carbide coatings produced using different spraying technologies.

Numerical and Experimental Investigations of CoNiCrAlY Particle Suspension Dynamics in Kerosene-Oxygen High Velocity Oxygen Fuel Spraying

Three-dimensional computational fluid dynamics (CFD) modelling is employed to simulate a typical high velocity oxygen fuel process (HVOF) under laboratory operating conditions. Two different modelling approaches, viz., the continuum and discrete models, are engaged to model the liquid fuel kerosene, and their influence on the resulting primary gas dynamics is investigated. Numerical results of the primary gas dynamics are validated against the available measurements and found to be in good agreement. It is observed that the fuel droplets less than 5 μm react completely inside the combustion chamber, whereas the larger droplets do not. With increasing fuel droplet size, the chemical reaction gets extended to the downstream of the combustion chamber, resulting in decreased flame temperature. Thus, it is inferred that a fuel droplet size of up to 5 μm yields better combustion characteristics. Discrete solid CoNiCrAlY particles are then injected into the high velocity primary gas stream, and their inflight dynamics are simulated. Results reveal that a maximum mean particle velocity of 700 m/s and a maximum particle temperature of 1350 K may be achieved under the given operating conditions. Particle deposit shape and size are determined both numerically and experimentally and found to be in good agreement. The influence of substrate stand-off distance on the particle deposit characteristics is investigated and reported in detail.

Crack Evolution and Computational Model Based Thermal Stress Evaluation of Laser Cladding Based on HVOF Sprayed WC/Co Deposits

A comprehensive experimental study on the high-velocity oxygen-fuel (HVOF) sprayed tungsten carbide/cobalt (WC/Co) deposits using laser cladding was conducted. A response surface methodology based on a central composite design was used to analyze, predict and optimize the WC/Co deposits of the laser-based HVOF sprayed coatings. The morphologies and microstructures of the laser clads were characterized using optical microscope, scanning electron microscope and X-ray diffraction techniques. The crack behavior and residual stress-based fractures were explored. In addition, the relationships between the residual stress of the laser clad and three factors: laser power, scanning speed and stand-off distance were examined. Further, optimization of the control factors: laser power, scanning speed and stand-off distance to minimize the residual stress was attained using a response surface methodology. The resulting lower residual stress has decreased the fracture crack activities and did not easily induce delamination in the laser clads. Findings from this study would greatly contribute to optimizing the experiments and achieve an enhanced structural evolution in the protective coating of traditional handicraft products by laser cladding.

Thermal transport property correlated with microstructure transformation and structure evolution of Fe-based amorphous coating

The correlation between the thermal transport properties and microstructure features of amorphous coatings is crucial for reliable thermal insulation applications. In this work, an Fe48Cr15Mo14C15B6Y2 amorphous coating prepared by high-velocity oxygen-fuel spraying (HVOF) was employed to reveal this relationship under long-term heating. From the combined effects of the amorphous phase and unique coating structure, the proposed coating exhibits an extremely low thermal conductivity of 1.92 W/(m∙K), granting a significant potential for being as metal-based thermal barrier coatings. Isothermal annealing experiments below the glass transition temperature demonstrate that the thermal insulation property can maintain stability with prolonged annealing time, despite a slight degradation relative to the as-sprayed coating which is ascribed to structural relaxation. Although nearly full crystallization can be slowly induced by annealing at the critical temperature of 600 °C, the thermal conductivity displays a distinct two-stage variation with annealing time, which is primarily attributed to the sluggish sintering of the coating structure. Moreover, grain growth and rapid structural sintering result in a drastic degradation of thermal insulation in the early stage of annealing at 850 °C, whereas grain growth upon prolonged annealing governs further variation of thermal conductivity. The results of this study not only provide important insights into the degeneration mechanism of thermal insulation of Fe-based amorphous coating, but also present an inspiration for exploring the degeneration mechanism of the most metallic coatings serving at high temperatures.