Fe-based Amorphous Coatings Research Articles

Effect of Sealing Treatment on the Corrosion Resistance of Detonation-Sprayed Fe-Based Amorphous Coating

Effect of Sealing Treatment on the Corrosion Resistance of Detonation-Sprayed Fe-Based Amorphous Coating

Study of friction and wear behaviors of Fe-based amorphous coatings by MD simulations

In this study, molecular dynamics simulation is adopted to investigate the friction and wear mechanism of Fe-based amorphous composited coatings. It was found that the ceramic phase can improve plasticity of the composite coatings to reduce wear. In addition, when the Al2O3 content is 15 wt%, due to the stress concentration between ceramic phase and amorphous phase, the viscosity flow in the amorphous phase results in plastic deformation. Through this, the best wear resistance has been obtained. In addition, with the increase of compression depth, the number of atoms accumulated constantly increases, and the degree of plastic deformation becomes higher in the composite coatings. Finally, a high sliding speed results in the reduction of the wear resistance of coatings.

Quantitative Estimation of Fe-Based Amorphous Coating Thickness Based on Pulsed Eddy Current Technology

Fe-based amorphous coatings prepared by high-velocity oxy-fuel (HVOF) spraying have the advantages of good mechanical properties, high density, low porosity, and high amorphous content. The service life and bonding strength of coating greatly depend on its thickness; however, the characterization of ferromagnetic coating thickness is a very difficult problem. Pulsed eddy current (PEC) is characterized by abundant signals in frequency domains. In this paper, the thickness measurement principle of ferromagnetic coating was explored, and the typical and entropy features from PEC signals were extracted. Seven integrated learning methods were combined to quantitatively characterize the coating thickness, namely ridge regression (RR), lasso regression (LR), random forest regression (RFR), extra trees regression (ETR), gradient boosting tree regression (GBTR), addaptive boost regression (ABR) and eXtreme Gradient Boosting Regression (XGBR) algorithms. By comparing typical features with new ones, it was verified that the effective combination of entropy features and typical features could be used as effective feature parameters of eddy current signal. Statistical scores (RMSE and R2) and GridsearchCV features were used to evaluate and optimize the established model. As indicated by the results, the proposed XGBR machine learning model well predicted the coating thickness, and the relative error less than 0.05 mm.

Electrochemical response and passivation affinity of Fe-based amorphous HVOF coatings prepared from pig iron on mild steel

The present work discusses the passivation tendency and corrosion resistance of a novel Fe66.59C11.70P7.58Mn0.37Si2.86Cr1.72Mo0.92B8.26 amorphous coating prepared from pig-iron deposited on mild steel using a high-velocity oxy-fuel (HVOF) thermal spray process. A quantitative assessment of the micromorphological features developed on each coating after the fabrication has been provided. The polarization response, current-transient at the potential in the passive zone, and gravimetric evaluations after 30 days of the salt-fog test using 3.5 w/v % NaCl solution were recorded to understand the overall corrosion behavior of the HVOF coatings. A steady-state electrochemical impedance measurement was also performed. The spectroscopic examination of the corrosion product was performed to understand the nature of passivation, and it revealed the formation of protective iron-chromate and phosphate phases on all the coatings. The synergistic effect of these protective phases and iron-based protective rust phases is believed to be the primary reason for the strong passivation of the coatings. Also, it has been proposed that the corrosion rates calculated from dynamic polarization response should not be considered as final assessment for corrosion resistance of the coatings. Rather, long term corrosion assessment is important to understand the benefit of amorphous coatings with lean chemistry of passive elements, like Cr.

Effect of HVOF Spraying Process on Particle Behavior of Fe-Based Amorphous Alloy Coatings

Effect of HVOF Spraying Process on Particle Behavior of Fe-Based Amorphous Alloy Coatings

Microstructure and Tribological Behavior of Supersonic Atmospheric Plasma-Sprayed Mo-/Fe-Based Amorphous Coating

Microstructure and Tribological Behavior of Supersonic Atmospheric Plasma-Sprayed Mo-/Fe-Based Amorphous Coating

Preparation of eco-friendly natural rosin-based SiO2–NH2@GO hybrid sealant and study on corrosion resistance of Fe-based amorphous coating for steel substrate

Sealing treatment is an effective method to prolong the service life of Fe-based amorphous coatings for steel substrates. Common sealants always have the disadvantages of releasing amounts of volatile organic compounds (VOC) and are expensive, prompting researchers to develop an eco-friendly, low cost and high-performance sealant. However, their simultaneous improvement is restricted by some inevitable contradictions among them. Herein, natural rosin was introduced as a sealing material and an eco-friendly natural rosin-based SiO2–NH2@GO hybrid sealant was successfully prepared by the sol-gel method. In addition, the functional nanocomposite SiO2–NH2@GO was added to the hybrid sealant system to achieve the purpose of extending the service life of the sealant. The filling efficiency, adhesion, thermal stability and long-term corrosion resistance of hybrid sealants were investigated. The study showed that the adhesion of the hybrid sealant to the Fe-based amorphous coating was improved by 10.59% after adding the nanocomposite. The hybrid sealant reaches maximum thermal decomposition at 414.3 °C. The corrosion current density (icorr) of the sample NSG-0.5‰ still decreased by about two orders of magnitude after immersion for 672 h (0#, icorr = 1.39 × 10−4 A/cm2; NSG-0.5‰, icorr = 1.51 × 10−6 A/cm2). Full immersion experiments explore the failure process of hybrid sealants, where corrosion always tends to propagate with unmelted particles. The hybrid sealant prepared has the advantages of being eco-friendly and low cost, and provides a specific preparation process, which provides a new direction for the development of the sealant.

Microstructural evolution of Fe-based amorphous alloy coatings via ultrasonic vibration-assisted laser cladding

• The coatings have a four-layer structure from the crystal to the amorphous phase. • The crystallisation width increases by 35 μm due to ultrasonic energy. • The formed columnar dendrites break and recrystallise due to ultrasonic streaming. Fe-based amorphous coatings were fabricated using laser cladding with and without ultrasonic vibration. The effect of ultrasonic vibration on microstructural evolution was studied in this paper. When compared with Fe-based amorphous coatings fabricated via laser cladding without ultrasonic vibration, the crystallisation zone at the bottom of the coating increases from 46 μm to 81 μm. It has a wavy distribution that is produced via the thermal effect and high-frequency disturbances due to ultrasonic vibration. The formed columnar dendrites break and recrystallise to form equiaxed crystals as a result of the stirring caused by ultrasonic-vibration induced streaming. However, the amorphous phase still dominates the top zone of the coating, which is less affected by ultrasonic vibration. The entire coating has a four-layer gradient microstructure from the crystalline phase to the amorphous phase, which is instrumental in reducing stress in the bonding area between the coating and substrate.

Electrochemical and passive film evaluation on the corrosion resistance variation of Fe-based amorphous coating affected by high temperature

The comprehensive effects of high temperatures and corrosive environments tend to cause grievous damage to the workpieces. In this paper, the effect of high temperature on the corrosion resistance of Fe-based amorphous coatings was studied. And the corrosion kinetics and variation of passive film characteristics of coatings at 25°C and 105°C were investigated by potentiodynamic polarization curves, electrochemical impedance spectroscopy, Mott-Schottky analysis, and et al., respectively. It was found that high temperature accelerated the corrosion process, as well promoted the thickening of passive films, and had a dissimilar influence on iron ions of different chemical valences synchronously. Besides, the increase in dopant concentrations and the structural change of the passive film were the main factors affecting the corrosion resistance.

Reinforced mechanical properties of plasma-sprayed Fe-based amorphous composite coatings by in-situ TiNx/TiOy

Ceramic particle-reinforced Fe-based amorphous coatings have received extensive attention due to their excellent strength and wear resistance. In this paper, TiNx/TiOy -enhanced Fe-based amorphous coatings were prepared by reactive plasma spraying technology, and the effect of eggshell-like TiNx/TiOy on the comprehensive mechanical properties of Fe-based amorphous coatings was systematically studied. The results showed that the hardness of the composite coating was significantly higher than that of the amorphous single-phase coating. Moreover, indentation experiments showed that TiNx/TiOy effectively confined crack growth in the amorphous phase. Though the bonding strength of the composite coating was lower than that of the pure amorphous coating, but still maintained a high bonding force of 20.68 MPa. Through the wear experiment, it was found that the wear scar of the composite coatings appeared plastic deformation, the friction coefficient and wear mass loss were both greatly reduced, and the optimal wear performance appeared in the composite coating with 15% Ti addition. In addition, SEM, EDS analysis, and the first-principles simulation results demonstrated the good bonding between Ti-containing compounds and Fe-based alloys.

Fe-based amorphous coating for high-temperature wear, marine and low pH environments

Fe-based amorphous coatings have been manufactured by the high-velocity oxygen fuel (HVOF) process to explore their applications for high-temperature wear, marine and acidic corrosion environments. The microstructural and mechanical characterization of the coating was performed using XRD, SEM-EDS, micro and nanoindentation techniques. The dry sliding wear performance of the coating was analyzed against an Al2O3 ball at room temperature (RT) and 600°C. In addition, the corrosion behaviour of coating was evaluated in filtered seawater and 0.5M H2SO4 solutions. The coating retained the amorphous state. Substantial enhancement in nano and micro-mechanical properties were observed after exposure at 600°C. Dry sliding wear tests indicated that the coating displayed three times better wear resistance at 600°C than at RT. The combined effects of enhanced mechanical properties due to nanocrystal precipitation and stimulated splat-to-splat cohesion behaviour and a compact, dense oxide glazed layer improved the overall wear resistance at 600°C. The coating exhibited higher corrosion resistance than 316L stainless steel and other Fe-based amorphous coatings in seawater and acidic solutions. In both environments, the coating demonstrated passivation behaviour derived from a layer composed of a stable Cr-based oxide reinforced with Mo and W-based oxides.

Enhancing the impact resistance of HVAF-sprayed Fe-based amorphous coatings via hierarchical structure design

Hierarchical structure has been proposed as an effective strategy for improving mechanical properties in many traditional alloy systems. In this work, using a similar structural design strategy, hierarchical structured Fe-based amorphous coatings comprising two layers with different porosities were successfully prepared by controlling the thermal spraying process parameters. Impact test revealed that hierarchical structure designed coatings exhibited enhanced impact resistance than that of the monolithic structured counterpart. Microstructure examinations demonstrated that compared with the monolithic structured coating, the introduction of hierarchical structure could not only effectively passivate the cracks, but also deflect the propagation path of the cracks, which directly or indirectly enhanced crack propagation resistance. Based on this, theoretical analysis and finite element simulations were systematically performed to reveal the intrinsic reasons for the improved impact toughness in hierarchical structured coatings, centering around the influence of hierarchical structure on the absorption rate of impact energy and the stress distribution of coating during the impact process. In summary, the current study opens another promising window to enhance the impact resistance of amorphous coatings.

The influence of laser surface texture parameters on the hydrophobic properties of Fe-based amorphous coatings

In this paper, the texture with different shape parameters was obtained by laser modification on the surface of Fe-base amorphous alloy coating prepared by plasma spraying. The phase was studied by X-ray diffraction technique. Its microstructure was studied by scanning electron microscopy (SEM). The effect of different parameters on hydrophobicity and its mechanism were studied by contact Angle test. The experimental results show that the best hydrophobicity angles of the coating surface are 146.7° ± 2.2° and 149.1° ± 1.9° for pits and honeycomb textures with center distance of 200 μm, respectively. The hydrophobic Angle of the honeycomb texture surface has no obvious change trend, and the hydrophobic Angle of the pitted texture coating surface decreases with the increase of the center distance.

Synthesis of novel waterborne silicone modified acrylic sealant and its corrosion resistance in Fe-based amorphous coatings

Porosity defects inevitably existed in the atmospheric plasma spraying (APS) Fe-based amorphous coatings, which directly affected the service lives of the coatings. Thus, sealing treatment became an effective method to improve the coatings' corrosion resistance and prolong their service lives. In this study, a waterborne silicone modified acrylic emulsion (WAE) was synthesized by emulsion polymerization and used as the main film-forming to prepare a waterborne silicone modified acrylic sealant (WAS) with both sealing and anticorrosion. Heat resistance analysis showed that the maximum decomposition temperature of WAS was 409 °C. Energy Dispersive Spectroscopy (EDS) test indicated that the water sealant penetrated to a depth >70 μm. Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) investigated the long-term corrosion resistance of the sealed coating. The results show that the waterborne sealant promotes the integrity of the passive film of the coating after sealing with the waterborne silicone modified acrylic sealant. After immersion for 34 days, the corrosion current density of the sealed coating decreased by more than one orders of magnitude (SR-3, icorr = 6.3 × 10−4A/cm2; Sample 0, icorr = 7.2 × 10−3A/cm2), and the coating protection efficiency (η) remained above 90 %. Considering the solvent-free property and excellent long-term corrosion resistance of the sealant, it provides a new direction for the research and development of functional waterborne coating.

Evolution in microstructure features and properties of Mo-containing Fe-Cr-Ni-B-Si composite coatings by laser cladding

The nano-crystalline strengthening Fe-based amorphous composite coatings were successfully prepared by optical laser cladding technology. The influence of Mo content on the microstructure, mechanical, corrosion and tribological properties of Fe-Cr-Ni-B-Si composite coatings were studied. Results indicated that the phase composition and the relative content of amorphous changed obviously with the increases of Mo content. The microstructure could transform from coarse columnar into disorder amorphous matrix accompanying nano-precipitates of Fe-based composite coating with the appropriate Mo content, and while the excessive Mo element caused severe segregation of MoSi2 ceramic. The micro-hardness and plastic deformation resistance of the composite coatings dramatically improved due to the increased content of amorphous phases and in-situ nanocrystalline reinforcing, which had a favorable influence on the corrosion resistance and tribological property. The modified composite coating with the component of Fe41.4Cr16.2Mo10Ni5.4B1.5Si1.5 (atm.%) exhibited the most excellent mechanical properties (1102 HV), corrosion resistence (0.2216 μA/cm2) and wear resistance (2.96 × 10−6 mm3/N·m) among the three composite coatings. At this time, the modified coating had excellent resistance to pits corrosion and oxidation abrasive wear. However, the coating without Mo element occurred serious pits corrosion, abrasive and oxidation wear. The uneven distribution of MoSi2 brittle ceramic tended to the formation of microcracks and fatigue shedding for the composite coating with excessive Mo content.

Study on fabrication technology and corrosion resistance of Fe-based amorphous alloy coatings by high-speed laser cladding

In this paper, the AME201 Fe-based amorphous alloy coating was prepared by ultra-high speed laser cladding on the surface of 27SiMn alloy steel. The effects of technological parameters on the surface morphology, micro-structure and dilution rate of coating. Corrosion resistance and weight loss of matrix, AME201Fe coating, 316L coating and Fe901 coating were studied by salt spray corrosion test. The results show that the thickness of AME201Fe coating is mostly affected by powder feeding, laser power and scanning speed have a huge impact on the width of coating, and the dilution rate increased from 0.13% to 29% with the change of laser power, nearly several hundreds of times. The results of salt spray test show that the AME201Fe coating has the minimum weight loss value at each stage compared with the matrix, 316L coating and Fe901 coating, which can play a good role in surface protection because of less internal defects and no grain boundary dislocations.

Effect of Sealing on the Corrosion and Wear Resistance of Fe-based Amorphous Coating

Effect of Sealing on the Corrosion and Wear Resistance of Fe-based Amorphous Coating

Effect of Spraying Power on Microstructure, Corrosion and Wear Resistance of Fe-Based Amorphous Coatings

Effect of Spraying Power on Microstructure, Corrosion and Wear Resistance of Fe-Based Amorphous Coatings

Effect of Sealing Treatments on Erosion–Corrosion of a Fe-Based Amorphous Metallic Coating in 3.5 wt.% NaCl Solution with 2 wt.% Sand

In this study, a Fe-based amorphous metallic coating (AMC) was sealed with three sealants, i.e., stearic acid, aluminum phosphate and cerium salt, respectively. Two types of electrochemical tests, namely the ex situ electrochemical impedance spectroscopy test and the in situ potentiostatic polarization test, were conducted to evaluate the erosion–corrosion resistance of as-sprayed and as-sealed AMCs. The results show that the aluminum phosphate–sealed AMC exhibits the best erosion–corrosion resistance with the higher critical flow velocity compared with the as-sprayed AMC, which is attributed to the deep penetration of aluminum phosphate and high hardness of the sealed layer. In contrast, the sealants of stearic acid and cerium salt are easily removed by sand particle impacting, deteriorating their erosion–corrosion resistance.

Effect of forced cooling on the microstructure and properties of Fe-based amorphous composite coatings prepared by laser remelting

A forced cooling system with three cooling plates was designed to assist laser remelting, and the effects of forced cooling on the microstructure and properties of Fe-based amorphous composite coatings prepared by laser remelting were studied. Results show that the content and size of the precipitated crystalline phase decrease, and the crystallites become finer with an increase in the temperature gradient of the forced cooling device. When the temperature of the cooling plate drops to 200 K, the precipitation of the strengthening phase M23(CB)6 is inhibited, and only the α-Fe phase precipitates, which has a good toughening effect. The hardness of the coating decreases because the precipitation of the strengthening phase is inhibited. The wear and corrosion resistances of the coatings are significantly improved because of an increase in the content of the amorphous phase and solid solution strengthening of the α-Fe phase. However, lowering the temperature of the cooling plate does not result in better performance. At a cooling plate temperature of 200 K, the wear resistance of the coating is the best because the appropriate amount of α-Fe phase plays a toughening effect.