Fe-based Amorphous Coatings Research Articles

Evolution of Wear Mechanism Under Different Sliding Conditions of an Fe-Based Amorphous Coating Synthesized by Plasma Spraying

Evolution of Wear Mechanism Under Different Sliding Conditions of an Fe-Based Amorphous Coating Synthesized by Plasma Spraying

Significantly enhanced corrosion resistance for Fe-based amorphous coatings via sealing treatment: Based on hybridisation and superhydrophobicity strategy

Based on the synergistic effect of hybridisation-superhydrophobicity, a simple and facile spraying method was used to achieve efficient sealing of Fe-based amorphous metallic coatings. In this paper, we employed rare-earth neodymium salts as inorganic sealant raw materials and loaded low surface energy fluorosilanes into epoxy resins to act as organic sealant raw materials. The surface structure and chemical composition of the sealing coatings were systematically characterised. The sealing mechanism as well as the anti-corrosion mechanism of the coating were investigated intensively. The results indicate that the superior corrosion resistance and self-cleaning ability of the sealed coating stems from the inorganic–organic-complex trinity effect: the corrosion inhibition effect of Nd oxide deposited during the inorganic sealing process, the shielding effect of the resin in the organic sealing, and the cross-linking and superhydrophobicity behaviour (liquid repellency effect) of the FDTES-Nd3+-Fe2+ complexes formed on the surface of the coating. This work provides valuable guidelines and insights for the design of subsequent corrosion-resistant and sealing coating.

Cracking resistance behavior of HVAF-sprayed monolayer and hierarchical Fe-based amorphous coatings under bending stress

The bending strength and fracture toughness are two key indicators that determine the service performance of thermally sprayed Fe-based amorphous coatings (AMCs) in harsh environments. Unfortunately, due to the inherent heterogeneous porosity and limited thickness (typically <1 mm) of the coatings, obtaining these properties is constrained by traditional fracture analysis methods. To address this, a three-point bending combined with the digital image correlation (DIC) method, without prefabricating notch or removing substrate, was proposed in the current work, and the effect of hierarchical structures on the fracture performance of the coatings was successfully revealed. Excitingly, the results show that compared to monolayer coating, hierarchical structures comprising two layers with different porosities can realize the synergistic improvement in the fracture strength and fracture strain of the coatings by alleviating local stress concentration and inducing crack deflection. Further, a finite element method (FEM) was employed to gain insight into the intrinsic relationship between the coating microstructures and the crack evolution behavior. This work not only proposes a simple method for evaluating the fracture performance of Fe-based AMCs sprayed with high velocity air fuel (HVAF), but also presents an innovative idea for optimizing the coating's properties.

Multi-layer formation by oxidation and solid-state crystallization of cold sprayed amorphous coatings during dry sliding wear

Amorphous alloy coatings, known for the exceptional wear resistance, have emerged as a key solution for enhancing the wear performance of magnesium alloys under harsh environments. In this study, Fe-based amorphous alloy coatings were deposited on magnesium alloy by cold spraying technology, and the influence of microstructural evolution on the wear performance of coatings under dry sliding wear conditions was discussed. The results showed that a dense adherent oxide layer with a thickness of ∼700 nm comprising nanograins of less than 8 nm was formed at the outmost surface, which played a role of self-lubricating. Underneath, a 1 μm thick nanocrystalline-amorphous layer with nanograins of ∼20 nm dispersed in the amorphous alloy matrix was formed through in-situ crystallization induced by flash temperature. This composite structure prevented the formation of shear bands in amorphous alloys and enhanced the durability. Therefore, the transition from abrasive wear to adhesive wear was a consequence of the microstructural evolution from a dual-phase composite layer to a self-lubricating oxide layer.

Microstructure evolution mechanism of WB-doped Fe-based amorphous composite coating under proton beam irradiation

Fe-based amorphous coatings exhibit exceptional irradiation resistance attributed to their distinct topologically disordered structure, rendering them highly attractive for advanced nuclear energy applications. The incorporation of WB secondary phase doping can notably alter the coating to enhance its operational safety. In this investigation, three different Fe-based composite coatings, with varying WB doping levels of 5 %, 10 %, and 15 % were fabricated through the High-Velocity Oxy-Fuel (HVOF) spraying technique. Irradiation tests were conducted at room temperature utilizing a proton beam with an energy of 1.52 MeV to simulate neutron irradiation environment in a nuclear reactor. The microstructure evolution before and after irradiation was systematically investigated with XRD, SEM, and TEM techniques. The results demonstrated that proton irradiation induced free volume, crystallization and H bubbles evolution. The doping of WB diminished the proton implantation dose threshold for segregation in irradiation plateaus while enhancing the growth of precipitates around the damage zone by inducing the production of M23C6 carbides and, at the same time, increasing the probability of H bubble nucleation and growth. These findings provide insights for iterative updates in Fe-based amorphous materials, informing their further development and application.

Fracture toughness and cavitation erosion behavior of Fe-based amorphous composite coatings with Ni-coated Al2O3 addition

Fe-based amorphous composite coatings were prepared on 304 stainless steel substrates using atmosphere plasma spraying (APS), aiming to investigate the effect of Ni-coated Al2O3 particles addition on fracture toughness and cavitation erosion behavior of Fe-based composite coatings. The microstructure, phase composition, elastic modulus, microhardness and fracture toughness of the coating were characterized using scanning electron microscopy with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness tester and nanoindentation. The cavitation erosion behavior of Fe-based coatings was investigated by ultrasonic vibration cavitation method. Fe-based amorphous composite coatings exhibit a characteristic lamellar microstructure and reveal the presence of amorphous phases along with α-(Fe, Cr), NiO, Ni and Al2O3 crystalline phases. When the content of Ni-coated Al2O3 in coating increases from 0 wt% to 3 wt%, there is slight deterioration in porosity from 3.64 % to 4.75 % and fracture toughness from 2.579 MPa·m1/2 to 2.392 MPa·m1/2, yet an increase in microhardness from 925.4 HV0.5 to 1090.3 HV0.5. The composite coating with 3 wt% Ni-coated Al2O3 demonstrates the peak cavitation resistance and its cumulative mass loss is significantly reduced by 36.4 % compared to the pure Fe-based coating. The cavitation erosion failure of Fe-based amorphous composite coatings is predominantly characterized by the brittle fracture mechanism. The fundamental process driving cavitation erosion damage involves the material peeling and coating delamination instigated by intense micro-jet impact and shock wave propagation. The proposed Fe-based amorphous composite coatings can be applied to improve the anti-cavitation performance of components in contact with high-speed fluids, such as ship propellers and centrifugal pump blades.

Effect of microstructure of overlapping regions on the wear/corrosion resistance performance of laser cladded Fe-based amorphous composite coatings

The issue of crystallization during the laser cladding process poses a significant challenge to the application of amorphous coatings. In order to explore the practical application of Fe41.5Co12.2Cr7.4Mo37.3C0.3B0.5Y0.4Al0.4 (at.%) amorphous composite coatings, this study fabricated coatings with different scanning speeds. The aim was to delve into their crystallization processes and assess the consequential effects on the coatings’ properties. The study revealed that crystallization predominantly occurs in the coatings’ overlapping region, which can be divided into two zones: the overlapping transition zone (OTZ) and the overlapping heat affected zone (OHAZ). The crystallization extent within the OHAZ is higher than in the OTZ, attributable to the disparate cooling rates characteristic of each region. With increasing scanning speed, the OHAZ gradually increases and the OTZ decreases. The coating prepared at 2000 mm/min has excellent corrosion resistance (polarization resistance 10,814.2 Ω·cm2) and wear resistance (wear rate (8.88±0.378)×10–6 mm3/N·m).

Corrosion-resistant Gd particles-doped Fe-based amorphous coatings with excellent neutron absorption properties

A kind of novel Gd particles-doped Fe-based amorphous metallic coating (Gd-AMC) was designed and produced by thermal spraying technique. The thermal neutron absorption cross-section for the coating containing 4.8 wt% Gd is 14.7 times higher than that of borated stainless steel (BSS) substrate. It is also worth noting that the localized corrosion resistance for Gd-AMCs is considerably superior to that for BSS substrate, which is closely attributed to the rapidly formed protective passive film on amorphous matrix through novel “dissolution-passivation” processes. This work provided a new strategy for the design of corrosion-resistant neutron absorbing materials.

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

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

Effects of Cr and Mo content on the microstructure and properties of Fe-based amorphous composite coatings by laser cladding

In this study, we successfully produced Fe-based amorphous composite coatings on the surface of 45 steel using laser cladding technology, and the impact of the relative content of Cr and Mo elements on the microstructure, hardness, and wear resistance of composite coatings has been investigated. The results show that the microstructure of the coating changes from dendrite to amorphous nanocrystalline when the content of Cr and Mo is 20 and 15 wt. %, respectively. However, when the Mo element continues to be added, elemental segregation will be caused, resulting in a large number of brittle Fe–Cr–Mo intermetallic compounds and MoSi2 ceramic phases in the coating. Therefore, the appropriate element ratio can not only increase the amorphous phase content in the coating but also prevent elemental segregation. Among the three types of amorphous composite coatings studied, the Fe45Cr20Mo15B10Si10 (wt. %) composite coating exhibited the most favorable performance, primarily due to its highest amorphous content (43.33%). Through the interaction of the amorphous phase, α-Fe, Fe–Cr solid solution, and a small proportion of intermetallic compounds, this coating achieved a hardness of 1282.8 HV0.2, approximately five times that of the 45 steel substrate, and demonstrated superior wear resistance.

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.

Optimization of HVOF spraying parameters for enhanced Fe-based amorphous coatings: A taguchi approach

In this work, Fe57Cr15Mo8P10C7B3 amorphous coatings (ACs) were fabricated on 316L stainless steel (316L SS) substrate using high-velocity oxygen-fuel (HVOF) spraying technique. The Taguchi's method guided the design of L16 (43) orthogonal experiments to optimize the process parameters, including spraying distance, oxygen flow rate, and kerosene flow rate. Through statistical analyses, including signal-to-noise ratio analysis, analysis of variance (ANOVA), and response surface methodology (RSM), empirical relationships for evaluating the influence of these parameters on coating quality were established, with porosity as the primary metric. Our findings indicate a pronounced sensitivity of the porosity of the ACs to spraying conditions, in which oxygen flow rate has the most significant effect on the porosity of the ACs, while kerosene flow rate has the smallest impact. Meanwhile, it is predicted that a minimum coating porosity of 0.75 % can be achieved under the optimal deposition conditions of the spraying distance of 330 mm, the kerosene flow rate of 6.0 GPH, and an oxygen flow rate of 1900 SCF. Experimental validation confirmed these conditions, yielding coatings with superior coating quality and performance with a minimum coating porosity of 0.68 %, a microhardness of 826 ± 65 HV0.1, improved corrosion resistance in 3.5 wt% NaCl solution with a high self-corrosion potential of −0.37 V, a low self-corrosion current density of 1.08 × 10−6 A/cm2, and a low passivation current density of 1.16 × 10−5 A/cm2, and enhanced wear performance with a wear volume loss of only 4.00 × 10−5 mm3 N−1 m−1 and a friction coefficient of as low as 0.42 ± 0.022. The present study confirms the reliability of Taguchi's method in determining optimal HVOF processing parameters, evidenced by the consistency between theoretical predictions and experimental results.

Impact of cyclic thermal shocks on the electrochemical and tribological properties of Fe-based amorphous coating

Fe-based amorphous coatings hold immense potential for marine industries due to their remarkable properties, including high hardness, exceptional corrosion resistance, and outstanding wear resistance. However, their performance under thermal shock conditions, particularly in high-temperature applications, remains a topic requiring further investigation. In this work, a Fe-based amorphous coating with a composition of Fe48Mo14Cr15Y2C15B6 was successfully developed using High-velocity oxygen fuel thermal spraying. To assess the thermal shock resistance of the amorphous coating, we subjected them to thermal cycles at 300 °C for 150 times, followed by cooling in two different mediums: saltwater quenching and air cooling. The results revealed that the coating maintained excellent contact with the substrate and preserved mainly amorphous structure both in the as-sprayed condition and after thermal shocks. Interestingly, the differential scanning calorimetry (DSC) results indicated that the air-cooled samples exhibited greater structural relaxation and crystallization compared to the brine-quenched samples. This microstructure changes in the air-cooled samples resulted in inferior mechanical properties, such as wear resistance and hardness, compared to the brine-quenched and as-sprayed samples.

Investigation the effect of surface treatment on the mechanical properties of coating

AbstractThe study analyzed surface treatment's impact on mechanical properties of Fe-based amorphous coatings. Specimens underwent six-hour treatments at 670 and 770 °C using vacuum heat. Results revealed distinct mechanical features in the coating: Vickers hardness reached 755, scanning electron microscope images displayed glassy phases, showcasing good wear resistance and compressive residual stresses at around −55 MPa. A remarkable 122% increase in compressive residual stress was noted through combined vacuum heat treatment and sandblasting. Volume wear decreased from the initial 18 to 14 mm3 after treatment at 670 °C followed by sandblasting, indicating a 30% enhancement in wear resistance. Yet, using vacuum heat treatment at 770 °C negatively impacted the coating's properties.

Effect of Isothermal Annealing on the Corrosion Resistance of Detonation Sprayed Fe-Based Amorphous Coatings

Effect of Isothermal Annealing on the Corrosion Resistance of Detonation Sprayed Fe-Based Amorphous Coatings

Tensile fracture characteristics and optimization strategy of Fe-based amorphous coated AZ31B magnesium alloy

Fe-based amorphous coatings (AMCs) were deposited on AZ31B magnesium alloy substrates via detonation spraying. The study focused on assessing the influence of these coatings on the tensile properties, damage evolution, and primary factors affecting the samples through heat treatment, tensile testing, and finite element analysis. The research findings highlighted a detrimental effect of the AMC on both fracture elongation and tensile strength of the magnesium alloy substrate. Specifically, the thin-coated samples (237 μm) experienced a decrease of 52.4% and 12.8%, respectively, while the thick-coated samples (362 μm) were less affected due to the easy debonding of the coating-substrate interface. The study also emphasized the critical role of cracking resistance at the substrate near the interface in determining the overall tensile properties of the coating-substrate system. It was found that annealing heat treatment, which leads to the formation of equiaxial grains near the interface of the substrate, significantly improves the tensile properties. On the other hand, samples subjected to cryogenic cycling treatment (CCT), resulting in an increased zone of deformation twinning, displayed the most adverse effects on performance. Therefore, annealing heat treatment proves to be an effective method for improving the tensile properties of magnesium alloys coated with Fe-based AMC.

Effect of WC-10Co-4Cr Reinforcement Amount on Wear and Corrosion Resistance of Fe-Based Amorphous Coatings

Effect of WC-10Co-4Cr Reinforcement Amount on Wear and Corrosion Resistance of Fe-Based Amorphous Coatings

Abnormal fretting wear behavior of Fe-based amorphous coating

To promote the application of Fe-based amorphous coating (AMC)-protected magnesium alloys in fretting wear conditions, a Fe-based AMC with a thickness of about 164 μm was deposited on AZ31B magnesium alloy substrate by detonation spraying. The microstructure and fretting wear behaviors against GCr15 counterpart ball in different frequencies of the Fe-based AMC were studied in detail. The results show that the Fe-based AMC has a substantially complete amorphous structure, the porosity and surface hardness are ≤1.2 vol %, and 764.7 ± 37.5 Hv0.1, respectively. Therefore, the Fe-based AMC presents excellent fretting wear resistance, and its wear rate is almost 1/10 of that of AZ31B magnesium alloy, and 1/5 of that of high-velocity oxygen-fuel sprayed 316L stainless steel coating on AZ31B magnesium alloy substrate. The fretting wear behavior of Fe-based AMC was found to be sensitive to the fretting frequency: as the frequency increases from 5 to 100 Hz, the average steady-state friction coefficient increases from 0.77 to 1.07, but the wear rate exhibits an anomalous phenomenon, decreasing from 5.26 × 10−5 mm3N−1m−1 to 3.47 × 10−5 mm3N−1m−1. The improvement in wear rate is mainly attributed to the formation of an oxygen-rich river-like friction layer on the worn surface as the transient contact temperature increases with frequency, effectively suppressing delamination wear. Additionally, the occurrence of high transient frictional temperatures at high frequencies leads to evident crystallization within the coating, accompanied by the formation of nanocrystals, oxide films, and a large area river-like friction layer consisting of debris-compacted layers, which strengthens the Fe-based AMC. Consequently, the wear mechanism changes from delamination wear and abrasive wear at low frequencies to oxidative wear and adhesive wear at high frequencies, resulting in superior fretting wear resistance of the Fe-based AMC at high frequencies.

Laser remelting of high-velocity arc-sprayed Fe-based amorphous coating for improving corrosion resistance in 3.5 % NaCl solution with varying Na2S concentrations

In this study, high-velocity arc-spraying (HVAS) was employed to produce Fe-based amorphous coatings, and subsequent to that, laser remelting (LR) technology was applied on the as-sprayed coatings (ASC) to prepare laser remelted coatings (LRC). The corrosion resistance of both coatings was tested in 3.5 wt% NaCl solutions containing varying Na2S concentrations (0, 20, 50, 100, and 200 ppm) to accurately simulate the corrosion environment of offshore components. The corrosion behavior was investigated using electrochemical workstation, scanning electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The experimental results revealed that LR resulted in the elimination of defects in Fe-based amorphous coatings, a substantial reduction in porosity, the disappearance of the laminar structure, and the achievement of a homogeneous composition. The corrosion tendency of ASC and LRC both exhibited a pattern of initially decreasing, then increasing and finally decreasing with increasing sulfide concentration. This was attributed to the deposition of corrosion products on the surface and the dissolution of the corrosion products. When the sulfide concentration exceeded 50 ppm, the corrosion current density of both coatings slowly and was lower than that at 20 ppm, indicating that both coatings possessed strong corrosion resistance at higher sulfide concentrations. Highly polarized anions in solution (e.g. HS−, S2−) occupied vacancies in the passivation film, destabilizing the coating's passivation film and consequently diminishing its corrosion resistance. From the electrochemical analysis, it was evident that LRC exhibited greater corrosion resistance than ASC at all sulfide-containing solution concentrations, which was attributed to its smoother surface, denser structure and more stable passivation film.

Tribological behaviour of Fe-based amorphous coating at elevated temperatures

Fe-based amorphous coatings (AMCs) were deposited using detonation spraying technology to investigate its performance in high-temperature wear conditions. The results indicate that the detonation-sprayed Fe-based AMC possesses a dense structure, low porosity, high amorphous phase content. At 300 °C, the coating has a maximum wear rate of 6.53 × 10−6 mm3 N−1 m−1, which is almost three times that at room temperature. The main wear mechanisms are oxidative wear, accompanied by fatigue stripping wear and adhesive wear. At 500 °C, the wear scar surface demonstrates increased toughness, resisting plastic deformation due to high-temperature softening. Additionally, partial crystallisation occurs, leading to an overall increase in the hardness of coating. Combined, these factors reduce the wear rate of the coating.