Search Results (54)

As a critical component of scraper conveyors, the middle trough operates under harsh conditions for extended periods, making it prone to failure and thus reducing the overall service life of the equipment. To address this issue and extend its service life, this study incorporated different amounts of CeO₂ into Cr₃C₂/Fe-based composite coatings. It investigated the effects of CeO₂ on the coating’s phase composition, microstructural evolution, wear resistance and corrosion resistance. Results show that CeO₂ addition did not alter the coating’s phase composition. The composition remained α-Fe, M₂₃C₆ (M: Fe, Cr) and vanadium carbides. However, CeO₂ promoted the transformation from columnar grains to equiaxed grains and refined the grains. With increasing CeO₂ content, the composite coating’s mechanical properties gradually improved. The Ce2 coating exhibited the highest microhardness (923.08 HV_0.5), the lowest friction coefficient (0.31) and the lowest wear rate (0.00217 mm³/N·m). Its dominant wear mechanisms were abrasive wear and mild adhesive wear. In 3.5% NaCl solution, the Ce2 coating showed the highest corrosion potential (−0.82 V) and the lowest corrosion current density (2.04 × 10⁻⁶ A/cm²), indicating excellent corrosion resistance. This study provides theoretical support for preparing high-performance Cr₃C₂/Fe-based composite coatings. It clarifies the key mechanism by which CeO₂ regulates coating properties. The developed composite coating has broad application potential due to its excellent combined wear and corrosion resistance. It can be widely used for surface strengthening of vulnerable components in mining machinery such as scraper conveyors, offering important theoretical and technical support for improving the service life of scraper conveyor middle troughs. Full article

Laser cladding is an effective surface engineering technique to enhance the high-temperature performance of metallic materials. In this work, a Cr-Al-C composite coating was in situ fabricated on H13 steel by laser cladding to alleviate the performance degradation of H13 steel under severe thermomechanical conditions, particularly in high-temperature piercing applications. The phase composition, microstructure, microhardness, high-temperature oxidation behavior, and tribological performance of the coating were systematically investigated. The coating is mainly composed of a B2-ordered Fe-Cr-Al phase reinforced by uniformly dispersed M₃C₂/M₇C₃-type carbides, which provides a synergistic combination of oxidation protection and mechanical strengthening, offering a microstructural design that differs from conventional Cr-Al or Cr₃C₂-based laser-clad coatings. Cyclic oxidation tests conducted at 800–1000 °C revealed that the oxidation behavior of the coating followed parabolic kinetics, with oxidation rate constants significantly lower than those of the H13 substrate, attributed to the formation of a dense and adherent Al₂O₃/Cr₂O₃ composite protective scale acting as an effective diffusion barrier. Benefiting from the stable oxide layer and the thermally stable carbide-reinforced microstructure, the wear rate of Cr-Al-C coating is significantly reduced compared to H13 steel. At room temperature, the wear rate of the coating is 6.563 × 10⁻⁶ mm³/(N·m), about two orders of magnitude lower than 8.175 × 10⁻⁴ mm³/(N·m) for the substrate. When the temperature was increased to 1000 °C, the wear rate of the coating remained as low as 5.202 × 10⁻⁶ mm³/(N·m), corresponding to only 1.9% of that of the substrate. This work demonstrates that the Cr-Al-C laser-cladded coating can effectively improve the high-temperature oxidation resistance and wear resistance of steel materials under extreme service conditions. Full article

In this study, the effects of different Mn content and heat treatment on the microstructure and properties of CoCrFeNiTi coatings by laser cladding technology were investigated. Scanning electron microscopy, energy-dispersive spectrometry, and X-ray diffraction were used to analyze the structure and composition. The hardness and wear resistance were tested by a microhardness tester and a friction-wear tester. The results show that there are many intermetallic compounds rich in Ti and Ni between the grains. As the Mn content increases, the coating gradually transitions from a dual-phase structure of BCC and FCC to a single FCC structure. The hardness of the coating decreases gradually with the increase in Mn content due to the change in the phase structure, while the friction coefficient decreases slightly at first and then increases significantly. The main wear mechanisms of the coating are adhesive wear and abrasive wear. After heat treatment at 600 °C, petal-like Laves precipitates appear. The average microhardness of CoCrFeNiTi coatings after heat treatment is lower than before treatment, and the friction coefficient is higher than before treatment. The average microhardness of the coating increases slightly with the increase in the treatment temperature. The average friction coefficient of the coating obtained after heat treatment at 600 °C is only 0.5941 because of its uniform microstructure. Therefore, it is reduced by approximately 15% compared with the base metal. Full article

Coatings based on the eutectic alloy Fe–TiB₂–CrB₂ were obtained by detonation spraying and subjected to pulsed plasma treatment. Comprehensive studies of the microstructure, phase composition, and mechanical and electrochemical properties of the coatings were carried out using SEM, TEM, and XRD methods. The initial coatings are characterized by a typical lamellar structure with interlamellar pores and defects. After pulsed plasma treatment, pronounced compaction of the surface layer, grain refinement, and sealing of interlamellar voids and cracks are observed. The thickness of the modified zone is about 15–30 μm, and the structure becomes fine-grained and more uniform. According to XRD and TEM data, the main boride phases (TiB₂, CrB₂) remain stable, while the intensity of γ-Fe decreases and weak Cr₂₃C₆ peaks appear, indicating phase stabilization and diffusion hardening. After treatment, the microhardness of the near-surface zone increases from ~14 GPa to 17–18 GPa, confirming the strengthening effect. Electrochemical tests showed an increase in corrosion resistance: the corrosion potential shifts to the positive side by approximately 0.15 V, and the corrosion current density decreases by almost two times. Thus, the use of pulsed plasma treatment significantly improves the density, phase stability, hardness, and corrosion resistance of Fe–TiB₂–CrB₂ detonation coatings, making this duplex approach promising for use in conditions of intense wear and exposure to aggressive environments. Full article

In order to enhance the performance of 20# steel, this study successfully fabricated AlCoCrFeNi high-entropy alloy coatings with different WC contents (x = 0, 10, 20, 30 wt%) on its surface using plasma cladding technology. The effects of WC content on the microstructure, mechanical properties, and corrosion resistance of the coatings were systematically investigated. The results indicate that without WC addition, the coating consists of a dual-phase structure comprising BCC and FCC phases. With the incorporation of WC, the FCC phase disappears, and the coating evolves into a composite structure based on the BCC matrix, embedded with multiple carbide phases such as W₂C, M₇C₃, M_xC_γ, and Co₆W₆C. These carbides are predominantly distributed along grain boundaries. As the WC content increases, significant grain refinement occurs and the volume fraction of carbides rises. The coating exhibits a mixed microstructure of equiaxed and columnar crystals, with excellent metallurgical bonding to the substrate. The microhardness of the coating increases markedly with higher WC content; however, the rate of enhancement slows when WC exceeds 20 wt%. The hardness of 1066.36 HV is achieved at 30 wt% WC. Wear test results show that both the friction coefficient and wear rate first decrease and then increase with increasing WC content. The optimal wear resistance is observed at 20 wt% WC, with a friction coefficient of 0.549 and a wear mass loss of only 0.25 mg, representing an approximately 40% reduction compared to the WC-free coating. Electrochemical tests demonstrate that the coating with 20 wt% WC facilitates the formation of a dense and stable passive film in NaCl solution, effectively inhibiting Cl⁻ ion penetration. This coating exhibits the best corrosion resistance, characterized by the lowest corrosion current density of 1.349 × 10⁻⁶ A·cm⁻² and the highest passive film resistance of 2764 Ω·cm². Full article

This work investigated the effect of high-nitrogen/low-hydrogen mixed atmosphere heat treatment on the electrochemical corrosion and wear resistance of plasma-sprayed FeCoNiCrAl high-entropy alloy (HEA) coatings. The HEA coatings were sequentially prepared through annealing at 400, 600, and 800 °C for 6 h. The heat treatment method was conducted in a vacuum tube furnace under 0.1 MPa total pressure, with gas flow rates set to 300 sccm N₂ and 100 sccm H₂. The XRD results indicated that the as-deposited coating exhibited α-Fe (BBC) and Al_0.9Ni_4.22 (FCC) phases, with an Fe_0.64N_0.36 nitride phase generated after 800 °C annealing. The electrochemical measurements suggested that an exceptional corrosion performance with higher thicknesses of passive film and double-layer capacitance can be detected based on the point defect model (PDM) and effective capacitance model. Wear tests revealed that the friction coefficient at 800 °C decreased by 3.84% compared to that in the as-sprayed state due to the formation of a dense nitride layer. Molecular orbital theory pointed out that the formation of bonding molecular orbitals, resulting from the overlap of valence electron orbitals of different atomic species in the HEA coating system, stabilized the structure by promoting atomic interactions. The wear mechanism associated with stress redistribution and energy balance from compositional synergy is proposed in this work. Full article

The development of power engineering requires the introduction of new materials and technologies to improve the quality and durability of products. One promising direction is the creation of heat-protective coatings for the protection of working surfaces of turbine blades of gas turbine engines operating at temperatures up to 1000–1200 °C. Intermetallic coatings based on iron aluminides (Fe₃Al, FeAl) have high resistance to oxidation due to the formation of an oxide layer: Al₂O₃. However, their application is limited by brittleness due to the so-called third element effect, which can be reduced through alloying with chromium. In this study the processes of formation of Fe–Al–Cr intermetallic coatings produced by air plasma spraying and the mechanisms affecting their stability at high temperatures were investigated. Experimental studies included the analysis of the microhardness, wear resistance, and corrosion resistance of coatings, as well as their phase composition and microstructure. The results showed that the optimization of sputtering parameters, especially in the FrCrAl (30_33) mode, promotes the formation of a coating with improved tribological and anticorrosion characteristics, which is associated with its dense and uniform structure. These data have an important practical significance for the creation of wear-resistant and corrosion-resistant coatings applicable in power engineering. Full article

CoCrFeNiMn high-entropy alloy (HEA) composite coatings with 0, 10, and 20 wt% TiC are synthesized through laser cladding technology, and their corrosion and wear resistance are systematically investigated. The X-ray diffraction (XRD) results show that with the addition of TiC, the phases of TiC and M₂₃C₆ are introduced, and lattice distortion occurs simultaneously (accompanied by the broadening and leftward shift of the main Face-Centered Cubic (FCC) peak). Scanning electron microscopy (SEM) reveals that the incompletely melted TiC particles in the coating (S2) are uniformly distributed in the matrix with 20 wt% TiC, while in the coating (S1) with 10 wt% TiC, due to gravitational sedimentation and decomposition during laser processing, the distribution of the reinforcing phase is insufficient. When rubbed against Si₃N₄, with the addition of TiC, S2 exhibits the lowest friction coefficient of 0.699 and wear volume of 0.0398 mm³. The corrosion resistance of S2 is more prominent in the simulated seawater (3.5 wt% NaCl). S2 shows the best corrosion resistance: it has the largest self-corrosion voltage (−0.425 V vs. SCE), the lowest self-corrosion current density (1.119 × 10⁻⁷ A/cm²), and exhibits stable passivation behavior with a wide passivation region. Electrochemical impedance spectroscopy (EIS) confirms that its passivation film is denser. This study shows that the addition of 20 wt% TiC optimizes the microstructural homogeneity and synergistically enhances the mechanical strengthening and electrochemical stability of the coating, providing a new strategy for the making of HEA-based layers in harsh wear-corrosion coupling environments. Full article

Objective: This study was conducted to address the harsh working environment of agricultural machinery and improve the wear resistance of soil-contacting components such as rotary tiller blades, thereby extending their service life. Method: Plasma-cladding technology was employed to prepare an iron-based wear-resistant coating on the surface of rotary tiller blades. The following parameter combination was optimized using response surface methodology (RSM): a cladding current of 144A, a cladding speed of 23 mm/s, a powder feeding rate of 23 g/min, and a cladding distance of 12 mm. The microstructure morphology, phase composition, microhardness, and wear resistance of the wear-resistant cladding layer were investigated. Results: The results indicate that the interface of the cladding layer is clean and free from significant porosity or defects, exhibiting good metallurgical bonding with the substrate. The primary phases identified in the cladding layer include α-Fe, Cr₇C₃, Cr₂Fe₁₄C, and Cr-Ni-Fe-C solid solutions. The average hardness of the cladding layer is 1171 Hv0.5, approximately 2.9 times that of the substrate. In wet sand–rubber wheel wear tests under identical conditions, the weight loss of the cladding layer is only 1/21 that of 65Mn steel, with minimal wear morphology. Field trials showed that the wear of the cladding layer rotary tiller blade was reduced by 24.5% compared with the unclad blade. The presence of the cladding layer significantly protected the integrity of the cutting edge, ensuring the functionality of the rotary tiller blade in cutting and throwing soil; thus, its original appearance was maintained even after prolonged wear. The findings of this study can provide a valuable reference for the enhancement of wear resistance for other soil-contacting components. Full article

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. Full article

An Fe-based amorphous coating, with the composition Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂, was synthesized by the high-velocity oxygen fuel spray (HVOF) process on a substrate of AISI 1035. The effect of crystallization on the electrochemical and tribological properties of the HVOF-sprayed Fe-based coating was systematically studied. The XRD results validated the fully amorphous nature of the as-sprayed coating by showing a broad peak at 43.44° and crystallization of this coating after heat-treatment at 700 °C by demonstrating sharp peaks of Fe-, Mo-, and Cr-based carbides. After crystallization, an increase in the corrosion current density from 4.95 μAcm⁻² to 11.57 μAcm⁻² and in the corrosion rate from 4.28 mpy to 9.99 mpy, as well as a decrease in the polarization resistance from 120 Ωcm² to 65.12 Ωcm², were observed, indicating the deterioration of the corrosion resistance of the as-sprayed Fe-based coating. This can be attributed to the formation of porous ferrous oxide, providing an easy channel for charge transfer and promoting pit formation. However, a decrease in the coefficient of friction from 0.1 to 0.05 was observed, highlighting the significant improvement in the wear resistance of the Fe-based coating after crystallization. This can be associated with the precipitation of hard carbides (MxCy) at the boundaries of the crystallized regions. Full article

This study focuses on Fe-based laser cladding coatings containing varying levels of four elements, and the objective is to investigate the influence of TiC addition on the microstructural evolution, microhardness, wear resistance, and corrosion resistance of these Fe-based composite coatings. Fe/TiC composite coatings were prepared by incorporating 20 wt.% TiC into four types of Fe-based coatings. The coatings were characterized using X-ray diffraction (XRD), optical microscopy for microstructural observation, microhardness testing, friction and wear tests, and electrochemical analysis. The results indicate that the phases of the coatings are primarily composed of α-Fe and Cr₇C₃. Upon the addition of TiC, the TiC and Ni₃Ti phases were observed in the coatings. The coatings mainly consist of columnar crystals, dendritic structures, equiaxed grains, and cellular structures, with petal-shaped TiC particles distributed within the coating matrix. TiC effectively enhances the microhardness and wear resistance of the coatings. The average microhardness of the coatings increased from 455.8 ± 20.8 HV_0.2 to 802.8 ± 41.6 HV_0.2 with TiC addition. Simultaneously, the wear rate of coating A2 decreased from 1.51 × 10⁻⁶ g/(N·m) to 1.02 × 10⁻⁷ g/(N·m), indicating an order of magnitude improvement in wear resistance. However, TiC destroys the denseness of the Fe coating, the current corrosion density increases by 28% on average, and the corrosion resistance decreases significantly. Full article

To prepare a soft magnetic powder core, the magnetic powder surface has to be insulated by phosphating treatment. Organic chemicals such as ethanol and acetone are generally used as solvents for phosphoric acid, which may cause serious environmental problems. This work proposed deionized water as the environmentally friendly phosphating solvent for FeSiCr powder. The soft magnetic composites (SMCs) were prepared using phosphoric acid for inorganic coating and modified silicon polymer for organic coating. The effect of different phosphating solvents, including deionized water, ethanol, and acetone, on the structure and magnetic properties of SMCs were investigated. It is found that the solvent affects the phosphating solution’s stability and the phosphoric acid’s ionization. The phosphoric acid is more stable in deionized water than in ethanol and acetone. The phosphating reaction in deionized water is also more stable in deionized water, resulting in a dense phosphate coating on the particle surface. The effects of phosphoric acid concentration and temperature on the magnetic properties of FeSiCr-based SMCs were further studied. With the increase in phosphoric acid concentration and temperature, the magnetic permeability and saturation magnetization of the powder core decrease, and the core loss decreases, followed by an increase. The optimized combination of properties was obtained for the SMCs phosphated with 0.2 wt.% phosphoric acid in deionized water at 35 °C, including a high effective permeability μ_e of 25.7, high quality factor Q of 80.2, low core loss P_cv of 709.5 mW/cm³ measured at 0.05 T @ 100 kHz, and high withstanding voltage of 276 V, due to the formation of uniform and dense insulating coating layers. In addition, the SMCs prepared with phosphated powder show good corrosion resistance. The anti-corrosion properties of the SMCs using deionized water as a phosphating solvent are better than those using ethanol and acetone. Full article

In this paper, a brake cylinder coating comprising a composite material of an Fe₃Al and Cr₃C₂ mixed powder was prepared by adding laser cladding onto carbon structural steel. We studied the influence of process parameters on the microstructure and tribological properties of the cladding materials using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and 3D white light interferometer and wear tests. The influence of different processes on the morphology of the carbide strengthening phase was found to be relatively small with a Cr₃C₂ content of 15 wt.%. The carbides mainly exhibited a network structure in each group of cladding layers. The area of the network strengthening phase varied under different processes. Of the cladding layers formed with different processes, the scanning speed of the 0.003 m/s cladding layer had the lowest wear rate. When the laser power was too low or the powder feed rate was too high, unmelted Cr₃C₂ particles could be found in the cladding layer. During the wear process, the particles peeled off, causing severe abrasive wear. When the powder feeding rate was too low, more materials in the base material entered the cladding layer. This made the composition of the cladding layer similar to that of the grinding material, resulting in severe adhesive wear. Full article

A novel graphene-coated nanocrystalline ceramic particle, iron-based composite inoculant was developed in this study to optimize the as-cast microstructure and mechanical properties of W18Cr4V high-speed steel (HSS). The effects of the composite inoculant on the microstructure, crystal structure, and mechanical properties of HSS were analyzed using transmission electron microscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The (00$\stackrel{\mathrm{-}}{2}$) and (020) crystal planes of the Fe₃C and Cr₇C₃ phases, respectively, were collinear at two points in the reciprocal space, indicating a coherent relationship between the Fe₃C and Cr₇C₃ phases in the tempered modified HSS. This contributed to an improved non-uniform nucleation rate and refining of the HSS grains. The mechanical properties of the modified steel exhibited a general improvement. Specifically, the modification treatment enhanced the hardness of HSS from HRC 63.2 to 66.4 and the impact toughness by 48.3%. Full article