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This study evaluates the tribological performance of Fe-based composite coatings for aerospace and automotive applications, focusing on wear resistance at elevated temperatures. The coatings, comprising 15% WC-Co and Cr3C2 in an SS316L matrix, were deposited onto maraging steel via HVOF spraying. Microstructural analysis and adhesive strength testing confirmed strong particle bonding, with the coatings achieving a hardness of 711 ± 14 HV. Dry sliding wear behaviour was assessed using a ball-on-disc tribometer with alumina as the counterface under 10 N and 30 N loads at 25 °C, 300 °C, and 600 °C. Results indicated a decrease in the coefficient of friction and specific wear rate with increasing load and temperature. At 600 °C, wear rates were reduced by ∼97.56% (10 N) and ∼97.12% (30 N) than uncoated steel. Abrasive wear dominated at room temperature, while adhesive and oxidative wear mechanisms emerged at 600 °C, attributed to protective glaze layer formation. [ABSTRACT FROM AUTHOR]

This paper provides a comparative evaluation of the mechanical properties, corrosion resistance, and gamma-ray shielding performance of four different types of tungsten carbide (WC)-NiCr coatings deposited on cold-rolled steel surfaces, which are used as materials for low- and intermediate-level radioactive waste (LILW) storage containers. The four types of coatings were classified as WC-85, WC-73, WC-66, and WC-39 according to their WC content and were applied to the cold-rolled steel surfaces using the High-Velocity Oxygen Fuel (HVOF) spraying process. The performance of the layered coatings was analyzed in terms of their microstructure, hardness, wear resistance, adhesion strength, corrosion properties, and gamma-ray shielding characteristics. Coatings with elevated WC contents showed enhanced mechanical properties and gamma-ray shielding effectiveness, whereas coatings with relatively lower WC contents and higher NiCr contents exhibited greater corrosion resistance. This paper discusses the performance of WC-NiCr coatings from the viewpoint of enhancing the durability and safety of commercial LILW storage containers. [ABSTRACT FROM AUTHOR]

The escalating demand for advanced structural materials with superior wear and corrosion resistance in aeronautical and military applications has spurred interest in amorphous alloys, particularly metallic glasses, due to their non-crystalline atomic configurations and exceptional mechanical properties. High-Velocity Oxygen Fuel (HVOF) spraying, a high-performance thermal spray technology, has emerged as a robust solution for enhancing the surface integrity of these materials by delivering dense, well-bonded coatings. This study investigates the integration of HVOF in reinforcing amorphous materials, with a specific focus on augmenting wear resistance under extreme mechanical stresses and improving corrosion protection in hostile environments. Key parameters such as particle velocity, flame temperature, and spray distance are analyzed to optimize coating quality while preserving the amorphous phase. The article delves into the microstructural evolution during deposition, assessing the resultant performance improvements through empirical data and computational models. Findings indicate that HVOF reinforcement significantly enhances the operational longevity of amorphous materials, positioning them as viable candidates for high-stress, corrosive conditions in military aviation, defense systems, and aerospace components.

The 316 stainless steel coatings with different thicknesses （SSC2， SSC4， SSC7， SSC10） were deposited on the magnesium alloy surface by using the HVOF method. The microstructures， deposition characteristics， residual stresses and immersion corrosion characteristics of the coating were investigated. The results reveal that due to the lower melting point and hardness of magnesium alloy， spray particles are prone to invade the substrate and melt its surface， causing particle escape or splashing， resulting in lower deposition efficiency； after depositing thinner coatings （SSC2 and SSC4）， the escape or splashing behavior of deposited particles reduces significantly， and the deposition efficiency increases； when the deposition thickness increases to SSC7 or above， the surface temperature of the deposition increases， particle splashing gradually increases， and the porosity and oxide content of the coating surface increase. Furthermore， as the coating thickness increases， the residual compressive stress of the coating decreases， the stress distribution becomes more uniform， and the number of penetrating pores in the coating decreases significantly， approaching zero. There are penetrating pores inside the SSC2 and SSC4 coatings， and the effective protection time is extremely short. The thick coatings （SSC7 and above） still have a protective effect after soaking in 3.5% （mass fraction） NaCl solution for 720 h.

In this research investigation, the optimization of the high-velocity oxygen fuel spray process parameters for achieving maximum coating thickness and minimum porosity percentage in VC coatings has been systematically explored. The study delved into the interplay of critical parameters including oxygen flow rate, LPG flow rate, and air flow rate, employing a Face Centered response surface methodology approach. Through a comprehensive analysis of interactive effects, response surface plots, and validation processes, this study uncovers profound insights that challenge conventional paradigms of coating optimization. Validation of the optimization parameters through experimental verification reaffirms the efficacy of the proposed model. The alignment between predicted and experimental results underscores the reliability of the optimization model in guiding parameter selections. Minor deviations observed further illuminate the delicate balance between theoretical precision and practical execution. The implications of this research extend to industries reliant on coatings, such as aerospace and manufacturing. The insights gained provide a roadmap for achieving not only desirable coating characteristics but also enhanced process understanding. [ABSTRACT FROM AUTHOR]

The current investigation examines the wear performance of High-Velocity Oxygen Fuel coated Colmonoy-88 coating on SS 304. An L9 orthogonal array design based on the Taguchi fractional factorial method was used to create the erosive wear tests. The impact of three parameters, such as impact velocity (100, 120, and 140 m/s), angle of impact (30°, 60°, and 90°), and test duration (10, 15 and 20 min), on wear performance was investigated by analysis of variance. Results show that the impact angle is the most vital factor for mass loss in both SS 304 and Colmonoy-88, followed by impact velocity and time duration. It was revealed that the maximum wear takes place at 30° impact angle in both specimens. The outcomes of the XRD and EDS analysis show that the Colmonoy-88 has a high chromium content, which provides it with exceptional erosion resistance. The Colmonoy-88 wear mechanism involved inter-splat micro-cutting, lips, crack initiations, and craters caused by fly ash particles at varying impact angles. [ABSTRACT FROM AUTHOR]

The in-flight behavior of quasicrystal (QC) particles during the high-velocity oxygen fuel (HVOF) process across four distinct operational settings was analyzed using computational fluid dynamics (CFD) simulations. A three-dimensional two-way coupled Eulerian–Lagrangian approach was used to simulate the process. The gas phase was modeled by solving equations governing mass, momentum, energy, and species, alongside the shear stress transport (SST) k-ω turbulence model, while the oxygen-propylene premixed combustion was simulated using the eddy dissipation model. Following the gas flow modeling, the trajectory and thermal evolution of QC particles were tracked within the computational domain, utilizing accurate correlations for drag coefficient and Nusselt number that cover a wide range of Mach, Knudsen, and Reynolds numbers. The analysis revealed that large particles do not melt due to their mass and the low thermal conductivity of QC materials. These particles typically attain impact velocities around 400 m/s. In contrast, smaller particles with diameters less than 20-25 μm reach temperatures of 1200 °C or higher, transitioning into a molten state with impact velocities reaching approximately 600 m/s. Moreover, it was found that approaching stoichiometric conditions with reduced mass flow rates of QC powder resulted in elevated particle temperatures and velocities upon impact, consequently leading to a reduction in porosity. To verify this finding, experiments were conducted under varying oxygen-to-fuel ratios and powder loadings, with subsequent measurement of the coating porosity. An in-flight particle diagnostic system was also used to assess the particle velocity. The numerical study agrees closely with the experimental observations. [ABSTRACT FROM AUTHOR]

Two WC-10Co-4Cr and WC-12Co coatings were deposited on the surface of AZ91 magnesium alloy using high velocity oxygen fuel (HVOF) technology aiming to improve the wear resistance and corrosion resistance. The hardness and organization of the surface and cross section of the coating and substrate were compared. The differences in wear resistance and corrosion resistance between the coatings and the substrate were compared. The wear experiments showed that the wear volumes of WC-10Co4Cr, WC-12Co and AZ91 substrate were 2.7 × 10-3 mm3, 1.1 × 10-3 mm3 and 6.1 × 10-1 mm3, respectively. The coatings mainly exhibited abrasive wear and adhesive wear. The better wear resistance of the coatings than the AZ91 substrate is due to the high hardness of the coatings. The corrosion resistance of the coatings was better than that of the substrate, and the corrosion resistance of WC-10Co-4Cr was better than that of WC-12Co. The corrosion currents density of WC-10Co4Cr, WC-12Co and AZ91 substrates are 4.02 μA cm-2, 34.31 μA cm-2 and 46.79 μA cm-2, respectively. The Cr element is favorable for further improving the corrosion resistance. [ABSTRACT FROM AUTHOR]

This research investigates; ways to improve material resistance to cavitation erosion and corrosion by using surfaces coated with PTFE and TiC applied through HVOF spraying. Optimal conditions were identified by the application of response surface methodology, leading to a significant decrease in mass loss. In material-specific reactions, HVOF-sprayed TiC showed increased resistance to cavitation because of its inherent micro-hardness (1293 HV). The reactivity of samples sprayed with PTFE varied, suggesting a complicated interplay between the properties of PTFE and jet velocities. SEM images verified the effectiveness of the PTFE and TiC coatings sprayed by HVOF as shields against corrosive elements. Even after seven cycles in a cyclic corrosion test, PTFE demonstrated outstanding corrosion resistance and impermeability, while the TiC coating created a dense, stable oxide layer. Furthermore, the combination of laser texturing and TiC and PTFE coatings sprayed with HVOF caused surfaces to exhibit superhydrophobic behavior (water contact angle: WCA > 155°). Extensive mechanical analyses provided information on surface roughness, bond strength, porosity, and microhardness, which helped to explain TiC's resilient resistance to indentation and strong adhesion (71.2 MPa) to the substrate. These findings offer practical methods and coatings to increase material resistance in conditions where cavitation and corrosive environments are common. [ABSTRACT FROM AUTHOR]

In this work, the effect of high-entropy alloy powder preparation on the coatings deposited via high-velocity oxygen fuel sprayings was studied. The powders of FeNiCoCrMo0.5Al1.3 composition were prepared by milling and gas atomization. The structures, porosity, phase composition, and microhardness of the coatings produced from mechanically alloyed and gas-atomized powders were compared. The influence of milling parameters on the powder phase composition and morphology was studied. Milling at 600 rpm for 1.5 h allowed the production of mechanically alloyed powder with a homogeneous distribution of Fe, Ni, and Al and thin lamellas enriched with Co, Cr, and Mo. Despite the difference in the feedstock powders' phase compositions, the phase compositions of the coatings deposited from mechanically alloyed and gas-atomized powders are the same consisting of BCC, FCC solutions, and oxide. The amount of FCC solutions and oxide in the coating depends on the size distribution of the sprayed powder. It was found that the phase composition and the properties of the coatings deposited from the mechanically alloyed and gas-atomized powders of similar sizes are similar. [ABSTRACT FROM AUTHOR]

This research paper focuses on the development of additive-based erosion-resistant high-velocity oxy-fuel (HVOF) WC-10Co4Cr coating for pump steel. In this study, the WC-10Co4Cr cermet powder consists of yttria and zirconia, each with a concentration of 3 wt.%. The HVOF spraying method was utilised to develop the ceramics-added WC-10Co4Cr coatings. The study conducted erosion tests using a pot tester under mining conditions. The microstructure, crystalline phases and microhardness of the as-HVOF coatings were analysed and compared between the pure and ceramics-based WC-10Co4Cr coatings. The results revealed the effect of ceramics addition on surface erosion of WC-10Co4Cr coating. The results indicate that yttrium oxide enhances the performance of WC-10Co4Cr coating in terms of erosion resistance, while zirconium oxide is not suitable for use in WC-10Co4Cr coating in erosion wear environments. [ABSTRACT FROM AUTHOR]

An investigation was conducted to analyze the mechanical properties, wear behavior, and microstructure of coatings formed by high-velocity oxygen fuel spraying of CoMoCrSi powders. The effects of varying Cr concentration and particle sizes before and after heat treatment at 900 °C for 4 h were studied comparatively. The increase in Cr and Mo elements in the expanse of Co increased the structure's hardness before and after the heat treatment. As this increase was 10% in as-sprayed conditions, annealing raised the increase to 30%. Splat boundaries were the most vulnerable constituents against forces, creating a significant disadvantage in terms of structural integrity and affecting the overall performance. After annealing, the boundary strengths experienced a remarkable four-fold increase and cracks and fractures reduced significantly. The susceptibility of splat boundaries had a detrimental effect on room temperature wear behavior, and increased boundary densities led to a marked reduction in wear performance. Heat treatment induced improvements significantly increased the room temperature wear performance. At elevated temperature, the formation of oxide layers composed of CoMoO4, Co3O4, MoO3, and Cr2O3 overcame the weaknesses of the as-sprayed coating, reducing both the friction coefficient and wear losses. A reduced Co ratio led to the formation of an oxide blend with a higher concentration of Mo and Cr oxides on the surface, further improving the coating's wear behavior. [ABSTRACT FROM AUTHOR]

Considering the significant health risks posed by hard chrome plating during its application, thermally sprayed Cr3C2-NiCr cermet coatings represent a suitable alternative. Incorporating hexagonal boron nitride (hBN) as a dry lubricant into the feedstock powder can further enhance wear resistance and thermal conductivity, crucial for preventing premature failure caused by inadequate lubrication. In this study, the mass fraction of hBN was varied between 0 and 15 wt.% to assess its influence on the tribological performance of the coatings using pin-on-disk tests. The coating's hardness was measured via the Vickers method, and its cracking tendency at the coating/substrate interface was evaluated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to analyze the microstructure and phase composition, while thermal diffusivity was determined using the laser flash method. The findings revealed that the inclusion of hBN, at concentrations of up to 10 wt.%, leads to an improvement in thermal diffusivity and a reduction in the coefficient of friction. However, exceeding this threshold leads to a decrease in hardness and increased crack formation tendency, highlighting the trade-off between frictional and mechanical properties. [ABSTRACT FROM AUTHOR]

Superalloys go through cyclic oxidation which refers to the progression of reputed exposure of materials to alternating oxidizing and non-oxidizing environments at high temperatures. The oxidation behavior of cobalt-based superalloy coatings depends on several variables, including the environment, surface roughness, manufacturing conditions, & coating composition. Because of their higher temperatures and protective oxide layer, coatings with a greater cobalt concentration are more oxidation-resistant. The behavior of oxidation is influenced by surface roughness, where rough surfaces offer greater surface area to oxidation while smooth surfaces decrease interaction with the environment. The microstructure and porosity of the coating are further impacted by processing variables used in thermal spraying, including temperature, particles velocity, and spray distance. Adding reactive components to the coating composition, such as silicon and aluminum, and applying post-treatments like nitriding or sealing are two ways to increase oxidation resistance. A greater temperature and particle speed can lead to a denser with less porous covering, improving the oxidation process resistance. The two typically used heat spraying techniques are high-velocity oxy-fuel (HVOF) and plasma spraying. To increase the resistance to oxidation of thermal spray cobalt-based superalloy coating, some strategies have been devised, such as inclusion of reactive materials, such as aluminum and silicon, which is the coating composition. These elements may establish an oxide layer protecting the coating's appearance, preventing further oxidation. [ABSTRACT FROM AUTHOR]

We studied a candidate TPS (thermal protection system) material for reusable re-entry space vehicle applications. The material was based on a high-temperature-resistant material called Cerakwool. A total of six specimens were fabricated with substrate densities of 0.45 g/cm3, 0.40 g/cm3, and 0.35 g/cm3, with two specimens for each density. All specimens were coated with high-emissivity TUFI (toughened unpiece fibrous insulation), with coating thicknesses ranging from 445 to 1606 µm. The specimens were tested using an HVOF (high-velocity oxygen fuel) material ablation test facility. For each density specimen pair, one specimen was tested at 1 MW/m2 and the remaining one was tested at 0.65 MW/m2. The average stagnation point temperature for specimens tested at 1 MW/m2 was ~893 °C, approximately 200 °C higher than those tested at 0.65 MW/m2. This suggests a ~200 °C increase in stagnation point temperature for a 0.35 MW/m2 rise in incident heat flux. During the tests, internal temperatures were measured at three locations. For all tested specimens, regardless of heat flux test conditions and density, the temperature at ~40 mm from each specimen's stagnation point remained around or below 50 °C, well within the 180 °C design limit set for the TPS back face temperature. Post-test visual inspections revealed no signs of ablation or internal damage, confirming the material's reusability. [ABSTRACT FROM AUTHOR]

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The focus of this research is to examine the feasibility of using laser texturing as a method for surface preparation prior to thermal spraying. The experimental part includes the thermal spraying of a Stellite 6 coating by High Velocity Oxygen Fuel (HVOF) technology on laser-textured substrates. The thermal spraying of this coating was deposited both on conventional substrate material (low carbon steel) and on substrates that had been previously heat treated (nitrided steel). The properties of the coatings were analysed using scanning electron microscopy (SEM), optical microscopy (OM) and Raman spectroscopy. Adhesion was assessed through a tensile adhesion test. The results showed the usability of laser texturing in the case of carbon steel, which was comparable or even better than traditional grit blasting. For nitrided steel, the problem remains with the hardness and brittleness of the nitrided layer, which allows for the propagation of brittle cracks near the interface and thus reduces the adhesion strength. [ABSTRACT FROM AUTHOR]

This study investigated the performance of High-Velocity Oxygen Fuel (HVOF)-sprayed Titanium Carbide (TiC) and TiC + 50C (50%TiC + 50%CoNi) coatings on SS316 steel under three-body abrasion conditions. The microstructural analysis revealed a homogeneous distribution of TiC particles within the TiC coatings, while the TiC + 50C coatings exhibited a more complex microstructure due to the presence of Co-Ni alloy. Mechanical testing demonstrated the superior microhardness of TiC coatings compared to the SS316 substrate, suggesting enhanced wear resistance. Slurry abrasion tests indicated reduced mass loss rates for both TiC and TiC + 50C coatings compared to uncoated SS316 steel, with TiC coatings exhibiting superior resistance to abrasive wear. Post-abrasion examination revealed distinct wear patterns, including abrasive chipping, plowing marks, crater formation, wear traces, and surface ruggedness. [ABSTRACT FROM AUTHOR]

The escalating demand for advanced structural materials with superior wear and corrosion resistance in aeronautical and military applications has spurred interest in amorphous alloys, particularly metallic glasses, due to their non-crystalline atomic configurations and exceptional mechanical properties. High-Velocity Oxygen Fuel (HVOF) spraying, a high-performance thermal spray technology, has emerged as a robust solution for enhancing the surface integrity of these materials by delivering dense, well-bonded coatings. This study investigates the integration of HVOF in reinforcing amorphous materials, with a specific focus on augmenting wear resistance under extreme mechanical stresses and improving corrosion protection in hostile environments. Key parameters such as particle velocity, flame temperature, and spray distance are analyzed to optimize coating quality while preserving the amorphous phase. The article delves into the microstructural evolution during deposition, assessing the resultant performance improvements through empirical data and computational models. Findings indicate that HVOF reinforcement significantly enhances the operational longevity of amorphous materials, positioning them as viable candidates for high-stress, corrosive conditions in military aviation, defense systems, and aerospace components. [ABSTRACT FROM AUTHOR]

High velocity oxy-fuel (HVOF) coating is a widely used thermal spray technique for applying wear-resistant coatings on metallic surfaces. The primary objective of this review is to provide an overview of the tribological properties of HVOF coatings. The review starts with a brief introduction to HVOF coatings, followed by a discussion of the various types of HVOF coatings and their microstructural characteristics. The tribological properties of HVOF coatings, including hardness, wear resistance, friction coefficient, and adhesion, are then discussed in detail. The influence of various parameters, such as coating material, substrate material, and testing conditions, on the tribological behaviour of HVOF coatings is also reviewed. A review of HVOF coatings tribology would cover the latest research on the subject, including the types of coatings available, their properties, and the methods used to evaluate their performance. It would also examine the challenges and opportunities in the field, such as developing new coatings for extreme environments or improving the coating-substrate adhesion. Finally, the review concludes with a summary of the key findings and suggestions for future research directions. Overall, this review highlights the potential of HVOF coatings to improve the tribological performance of metallic components in various industrial applications.

Application of Kaplan turbines is widespread in low-water-head and large-capacity hydropower plants. An understanding of the failure mechanism of Kaplan Turbines is a key factor to provide useful solutions for their prevention or early treatment and to guarantee their workability. The long-term performance of Kaplan turbines depends on many factors such as cavitation, erosion, fatigue, and material defects. Cavitation in Kaplan turbines leads to flow instability, vibrations, surface damage, and reduce the machine performance. Therefore, this paper investigates the factors leading to cavitation in Kaplan turbine and presents practical solutions for it. Thermal-sprayed coatings are frequently applied due to their high wear resistance, cost effectiveness, weight reduction, and less negative impacts on base metal. Moreover, HVOF is used to create coatings with a high density and bonding strength. At high temperatures, cermet coatings, including nanoparticles, exhibit exceptional wear resistance. WC-based nanostructured and multifaceted coatings are utilized due to their high wear resistance. In addition, chromium carbide in WC-based coatings increases their oxidation and wear resistance.

The current study aims to improve the mechanical and tribological properties of the thrust plate of the gear pump using High Velocity Oxy-fuel (HVOF) surface treatment. Further, this research focuses on the effects of different cooling mediums (Air, Water, Kerosene oil, Olive oil, and Hydraulic oil) on HVOF-treated samples of the thrust plate. The result shows that the micro-hardness of HVOF-treated samples has increased significantly by 142% (maximum ∼ 188 HV0.2) for water-cooled sample as compared to untreated sample (78 HV0.2). The coefficient of friction for the untreated sample was 0.44, whereas it was found to be 0.39, 0.27, 0.20, 0.06, and 0.04 for the HVOF-treated samples quenched in Water, Air, Kerosene, Olive oil, and Hydraulic oil, respectively. A significant increment in water contact angle (WCA) was observed for the HVOF-treated sample (hydraulic oil cooled - 111°) as compared to the untreated thrust plate sample (WCA - 61.8°). [ABSTRACT FROM AUTHOR]

Wear is a major issue in industry, particularly with metal components. Therefore, it is crucial to investigate methods that offer increased resistance to this phenomenon. In this research, three coating systems (pure WC-CoCr and WC-CoCr/NiCrFeSiBC+Mo, 88:12 and 83:17 wt.%) were thermally sprayed on an AISI 1018 steel substrate through the High-Velocity Oxygen Fuel (HVOF) process. The coatings were characterized using a field emission scanning electron microscope (FESEM) equipped with the energy dispersive spectroscope (EDS) and X-ray diffractometry (XRD). An analysis of the wear rate for ball-on-flat linear reciprocating sliding tribological tests for the coatings was also carried out. The coating microstructure presents well-dispersed NiCrFeSiBC splats. The WC-CoCr/NiCrFeSiBC+Mo, 88:12, system has the highest wear resistance, decreasing by 30.2% at high loads compared to commercial WC-CoCr CERMETs, and also exhibits the highest fracture toughness. Analysis of wear tracks shows that the material removal at all charges occurred mainly by an abrasive wear mechanism. [ABSTRACT FROM AUTHOR]

This paper presents and demonstrates the development of a new lightweight coating for aluminum alloy from a novel multicomponent alloy based on the AlSiMgCu system. The coating was applied using a newly designed approach that combined high velocity oxy-fuel (HVOF) and plasma spraying processes. This hybrid technique enables the deposition of coatings with enhanced performance characteristics. The optical microscopy (OM) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM + EDS) revealed a strong adhesion and compaction between the multicomponent coating and the A6061 substrate. The new coating improved hardness by 50% and increased electrical conductivity by approximately 3.3 times compared to the as-cast alloy. Corrosion tests showed a lower corrosion rate, comparable to thermally treated A6061 alloy. Tribological tests indicated over 20% reduction in friction and over 50% reduction in wear rate. This suggests that multicomponent aluminum coatings could improve automotive and parts in contact with hydrogen by enhancing hydrogen fragilization resistance, corrosion resistance, electrical conductivity, and wear properties, with further optimization of thermal spraying potentially boosting performance even further. [ABSTRACT FROM AUTHOR]

Thermal spray coating is a procedure that deposits many particles on the coating layer. This paper reviews thermal spray process numerical models. These models have both benefits and drawbacks. The future in the thermal coating process numerical simulation trends have been addressed in this article. The research closes with a numerical model analysis and development possibilities. FGCs solve traditional coatings' problems. It involves mathematical and computer simulations of FGC behaviour. To verify model accuracy, experimental data is compared to numerical model output. The numerical model shows stress distribution, thermal behaviour, and diffusion processes, allowing design optimisation. It also simplifies physics. FGC and numerical modelling can improve advanced engineering coating performance, durability, and functionality. Coatings can improve energy conversion, storage, and other applications. Future work includes using advanced numerical methods to increase model accuracy and creating new models for specialised purposes. [ABSTRACT FROM AUTHOR]

The materials used in concentrating solar power (CSP) systems are becoming of interest because of the high energy efficiency of energy storage. Molten salts can be used as both heat-storage media and heat-transfer fluid in a CSP system. In molten salts, steel alloys used in vessels and pipelines are highly vulnerable to hot corrosion. To protect steel alloys, applying a coating is an excellent strategy to extend the life of the alloy. NiCrAl coatings are well-suited for high-temperature environments. The purpose of this study was to investigate the corrosion behavior of NiCrAl with Si addition coatings on AISI304 in molten salt. NiCrAl coatings with and without Si addition were deposited using the high-velocity oxygen fuel (HVOF) technique. The corrosion test was performed using an immersion test in modified solar salt with 0.5% NaCl at 400–600 °C. Gravimetric methods evaluate the weight change for immersion tests. At 400 °C, an increased amount of weight gain due to the oxidation reaction and molten salt infiltration was observed. At 600 °C, the corrosion reaction was more dominant, and apparent oxidation was decreased; however, oxidation products NiO and sodium aluminum silicate were detected. Si addition supports the formation of the protective oxide sodium aluminum silicate, which inhibits molten salt oxidation reaction and molten salt infiltration. [ABSTRACT FROM AUTHOR]

Composite coatings based on chromium carbide (Cr3C2) and nickel–chromium alloys (NiCr) are widely used due to their unique properties, including high heat resistance, wear resistance and corrosion resistance. This article studies the structural–phase and physical–mechanical characteristics of Cr3C2-NiCr composite coatings applied by high-velocity oxygen fuel to E110 zirconium alloy. The HVOF method was chosen to create coatings with high adhesion to the substrate and excellent performance properties. Analysis of the microstructure of the cross-section showed the thickness of the modified surface layer from 75 to 110 μm, depending on the processing modes. Energy dispersive X-ray spectral analysis revealed the presence of elements Cr, Ni, C and O in the coating composition. Structural–phase analysis confirmed the formation of coatings with a high concentration of Cr3C2 carbide particles and NiCr (nickel–chromium) phases. The resulting composite coatings based on Cr3C2-NiCr had a significantly high microhardness, ranging from HV 1190 to HV 1280, and the friction coefficient varied in a significant range from 0.679 to 0.502 depending on the processing conditions. The maximum adhesion strength was 9.19 MPa per square centimeter. [ABSTRACT FROM AUTHOR]

High velocity oxy-fuel (HVOF) coating is a widely used thermal spray technique for applying wear-resistant coatings on metallic surfaces. The primary objective of this review is to provide an overview of the tribological properties of HVOF coatings. The review starts with a brief introduction to HVOF coatings, followed by a discussion of the various types of HVOF coatings and their microstructural characteristics. The tribological properties of HVOF coatings, including hardness, wear resistance, friction coefficient, and adhesion, are then discussed in detail. The influence of various parameters, such as coating material, substrate material, and testing conditions, on the tribological behaviour of HVOF coatings is also reviewed. A review of HVOF coatings tribology would cover the latest research on the subject, including the types of coatings available, their properties, and the methods used to evaluate their performance. It would also examine the challenges and opportunities in the field, such as developing new coatings for extreme environments or improving the coatingsubstrate adhesion. Finally, the review concludes with a summary of the key findings and suggestions for future research directions. Overall, this review highlights the potential of HVOF coatings to improve the tribological performance of metallic components in various industrial applications. [ABSTRACT FROM AUTHOR]