The Experts below are selected from a list of 15408 Experts worldwide ranked by ideXlab platform
Cheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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Effect of hydrostatic pressure on the corrosion behavior of HVOF-sprayed Fe-based Amorphous Coating
Journal of Alloys and Compounds, 2018Co-Authors: Cheng Zhang, Zhi-wei Zhang, Qi Chen, Lin LiuAbstract:Abstract Understanding corrosion behavior under hydrostatic pressure is crucial for the design of materials for deep-sea industrial applications. In this work, the corrosion behavior of a Fe48Mo14Cr15Y2C15B6 Amorphous Coating was examined under high hydrostatic pressure (80 atm), and compared to that at atmospheric pressure (1 atm). The results from immersion and potentiodynamic polarization tests indicate that the general corrosion rate of the Coating increased at 80 atm with respect to that at 1 atm, yet the localized corrosion resistance did not change much. However, the stability of passive films at 80-atm is declined compared to that at 1-atm, which is attributed to the lower compactness and higher density of point defects in the passive film at high hydrostatic pressure. Finally, TEM observations reveal that the passive film formed at 80 atm is much thicker (nearly 3 times) than that formed at 1 atm due to a faster dissolution rate of metals and diffusion rate of ions under high hydrostatic pressure, which have a compensation for the decrease of stability and compactness of the passive film, such that the good localized corrosion resistance of the Amorphous Coating is reserved at high hydrostatic pressure. This study sheds light on the dynamics of passive film formed on Amorphous metals and will also be helpful for designing corrosion-resistant materials for deep-sea applications.
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Toughening Fe-based Amorphous Coatings by Reinforcement of Amorphous Carbon.
Scientific Reports, 2017Co-Authors: Wei Wang, Cheng Zhang, Zhi-wei Zhang, Muhammad Yasir, Hai-tao Wang, Lin LiuAbstract:Toughening of Fe-based Amorphous Coatings meanwhile maintaining a good corrosion resistance remains challenging. This work reports a novel approach to improve the toughness of a FeCrMoCBY Amorphous Coating through in-situ formation of Amorphous carbon reinforcement without reducing the corrosion resistance. The Fe-based composite Coating was prepared by high velocity oxy-fuel (HVOF) thermal spraying using a pre-mixed Fe-based Amorphous/nylon-11 polymer feedstock powders. The nylon-11 powders were in-situ carbonized to Amorphous carbon phase during thermal spraying process, which homogeneously distributed in the Amorphous matrix leading to significant enhancement of toughness of the Coating. The mechanical properties, including hardness, impact resistance, bending and fatigue strength, were extensively studied by using a series of mechanical testing techniques. The results revealed that the composite Coating reinforced by Amorphous carbon phase exhibited enhanced impact resistance and nearly twice-higher fatigue strength than that of the monolithic Amorphous Coating. The enhancement of impact toughness and fatigue properties is owed to the dumping effect of the soft Amorphous carbon phase, which alleviated stress concentration and decreased crack propagation driving force.
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Fe-based Amorphous Coating for corrosion protection of magnesium alloy
Materials & Design, 2016Co-Authors: Shengfeng Guo, Fusheng Pan, Hongju Zhang, Ding-fei Zhang, Jingfeng Wang, J. Miao, Cheng ZhangAbstract:Abstract In this work, AZ61 magnesium alloy coated with NiCrAl intermediate layer with outer of Fe-based Amorphous Coating was fabricated by high-velocity oxy-fuel thermally spraying. Through the intermediate metallic Coating, the traditional mismatch of Fe-based materials and magnesium substrate was overcome, exhibiting good metallurgical bonding in the interface regions. The protective magnesium alloy with Fe-based Amorphous Coating possesses very high hardness and excellent corrosion resistance in 3.5% NaCl solution, demonstrating by nearly ten times of hardness higher and two orders of magnitude of corrosion rate lower than the magnesium substrate. Similarly to 316L stainless steel Coatings, the current Fe-based Amorphous Coating with a very large passive region, shows much more positive of corrosion potential and much less corrosion current density than that of sprayed Al alloy Coating and ceramic Coatings on magnesium alloys previously reported. The outstanding feature of the protective magnesium alloy with Amorphous Coating can be attributed to its unique disorder structure and uniform chemical composition, which allows a very dense passivation film formed and uniform corrosion occurred. Our findings demonstrate that Fe-based Amorphous Coating is a promising candidate for protecting magnesium alloys with desirable corrosion resistance for structural/functional applications.
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Pitting mechanism in a stainless steel-reinforced Fe-based Amorphous Coating
Electrochimica Acta, 2016Co-Authors: Cheng Zhang, Wei Wang, Lin LiuAbstract:Abstract There is keen interest in developing Fe-based Amorphous composite Coatings with superior bonding strength and mechanical properties for load-bearing applications. However, the interfaces between the added second phase and the Amorphous matrix always suffer from pitting corrosion in harsh Cl − solutions, leading to the degradation of performance of these composite Coatings. The underlying pitting mechanism has remained elusive. In this study, the pits initiation behaviour of a Fe-based Amorphous Coating reinforced with stainless steel powders is systematically investigated in a 3.5% NaCl solution through polarization, electrochemical noise, scanning Kelvin probe and ‘ in-situ observation’ measurements, as well as high-resolution transmission electron microscopy. The pitting resistance was found to be deteriorated obviously when stainless steel phase was added to the Amorphous Coating. The results indicated that pitting at the interfaces was not caused, as generally believed, by microgalvanic corrosion between the stainless steel phase and the Amorphous matrix, but caused by the formation of Fe 3 O 4 oxide at the interfaces due to the strong tendency towards oxidation of stainless steel particles in thermal spraying processes. This oxide is unstable in a Cl − -containing environment and acts as reactive sites for pits initiation. The present work emphasizes the effect of oxidation of the reinforcement on the pitting resistance of Amorphous Coatings and provides an alternative recommendation to the design of Amorphous composite Coatings for corrosion and load-bearing applications.
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Enhancement of impact resistance of Fe-based Amorphous Coating by Al2O3 dispersion
Materials Letters, 2016Co-Authors: Muhammad Yasir, Cheng Zhang, Wei Wang, Yongzhen Jia, Lin LiuAbstract:Abstract The load-bearing applications of Fe based Amorphous Coatings are limited due to their poor impact resistance. Here, we have designed an Amorphous composite Coating reinforced with 20 wt% Al 2 O 3 particles that is tougher and more impact resistant than the monolithic Amorphous Coating. Impact resistance of the Coatings was systematically studied by drop-weight impact tests and finite element modelling (FEM). It was found that the hard Al 2 O 3 particles in the composite Coatings could effectively hinder crack propagation via the formation of micro-cracks inside the Al 2 O 3 particles, which absorbs the impact energy. FEM indicates that the Al 2 O 3 dispersion acts as the main loading-bearing phase and alleviates the stress concentration in the composite Coating, thus suppresses crack initiation and propagation. Furthermore, electrochemical polarization test shows that composite Coating remains good corrosion resistance in a 3.5% NaCl solution after impact.
Lin Liu - One of the best experts on this subject based on the ideXlab platform.
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Effect of hydrostatic pressure on the corrosion behavior of HVOF-sprayed Fe-based Amorphous Coating
Journal of Alloys and Compounds, 2018Co-Authors: Cheng Zhang, Zhi-wei Zhang, Qi Chen, Lin LiuAbstract:Abstract Understanding corrosion behavior under hydrostatic pressure is crucial for the design of materials for deep-sea industrial applications. In this work, the corrosion behavior of a Fe48Mo14Cr15Y2C15B6 Amorphous Coating was examined under high hydrostatic pressure (80 atm), and compared to that at atmospheric pressure (1 atm). The results from immersion and potentiodynamic polarization tests indicate that the general corrosion rate of the Coating increased at 80 atm with respect to that at 1 atm, yet the localized corrosion resistance did not change much. However, the stability of passive films at 80-atm is declined compared to that at 1-atm, which is attributed to the lower compactness and higher density of point defects in the passive film at high hydrostatic pressure. Finally, TEM observations reveal that the passive film formed at 80 atm is much thicker (nearly 3 times) than that formed at 1 atm due to a faster dissolution rate of metals and diffusion rate of ions under high hydrostatic pressure, which have a compensation for the decrease of stability and compactness of the passive film, such that the good localized corrosion resistance of the Amorphous Coating is reserved at high hydrostatic pressure. This study sheds light on the dynamics of passive film formed on Amorphous metals and will also be helpful for designing corrosion-resistant materials for deep-sea applications.
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Toughening Fe-based Amorphous Coatings by Reinforcement of Amorphous Carbon.
Scientific Reports, 2017Co-Authors: Wei Wang, Cheng Zhang, Zhi-wei Zhang, Muhammad Yasir, Hai-tao Wang, Lin LiuAbstract:Toughening of Fe-based Amorphous Coatings meanwhile maintaining a good corrosion resistance remains challenging. This work reports a novel approach to improve the toughness of a FeCrMoCBY Amorphous Coating through in-situ formation of Amorphous carbon reinforcement without reducing the corrosion resistance. The Fe-based composite Coating was prepared by high velocity oxy-fuel (HVOF) thermal spraying using a pre-mixed Fe-based Amorphous/nylon-11 polymer feedstock powders. The nylon-11 powders were in-situ carbonized to Amorphous carbon phase during thermal spraying process, which homogeneously distributed in the Amorphous matrix leading to significant enhancement of toughness of the Coating. The mechanical properties, including hardness, impact resistance, bending and fatigue strength, were extensively studied by using a series of mechanical testing techniques. The results revealed that the composite Coating reinforced by Amorphous carbon phase exhibited enhanced impact resistance and nearly twice-higher fatigue strength than that of the monolithic Amorphous Coating. The enhancement of impact toughness and fatigue properties is owed to the dumping effect of the soft Amorphous carbon phase, which alleviated stress concentration and decreased crack propagation driving force.
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Pitting mechanism in a stainless steel-reinforced Fe-based Amorphous Coating
Electrochimica Acta, 2016Co-Authors: Cheng Zhang, Wei Wang, Lin LiuAbstract:Abstract There is keen interest in developing Fe-based Amorphous composite Coatings with superior bonding strength and mechanical properties for load-bearing applications. However, the interfaces between the added second phase and the Amorphous matrix always suffer from pitting corrosion in harsh Cl − solutions, leading to the degradation of performance of these composite Coatings. The underlying pitting mechanism has remained elusive. In this study, the pits initiation behaviour of a Fe-based Amorphous Coating reinforced with stainless steel powders is systematically investigated in a 3.5% NaCl solution through polarization, electrochemical noise, scanning Kelvin probe and ‘ in-situ observation’ measurements, as well as high-resolution transmission electron microscopy. The pitting resistance was found to be deteriorated obviously when stainless steel phase was added to the Amorphous Coating. The results indicated that pitting at the interfaces was not caused, as generally believed, by microgalvanic corrosion between the stainless steel phase and the Amorphous matrix, but caused by the formation of Fe 3 O 4 oxide at the interfaces due to the strong tendency towards oxidation of stainless steel particles in thermal spraying processes. This oxide is unstable in a Cl − -containing environment and acts as reactive sites for pits initiation. The present work emphasizes the effect of oxidation of the reinforcement on the pitting resistance of Amorphous Coatings and provides an alternative recommendation to the design of Amorphous composite Coatings for corrosion and load-bearing applications.
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Enhancement of impact resistance of Fe-based Amorphous Coating by Al2O3 dispersion
Materials Letters, 2016Co-Authors: Muhammad Yasir, Cheng Zhang, Wei Wang, Yongzhen Jia, Lin LiuAbstract:Abstract The load-bearing applications of Fe based Amorphous Coatings are limited due to their poor impact resistance. Here, we have designed an Amorphous composite Coating reinforced with 20 wt% Al 2 O 3 particles that is tougher and more impact resistant than the monolithic Amorphous Coating. Impact resistance of the Coatings was systematically studied by drop-weight impact tests and finite element modelling (FEM). It was found that the hard Al 2 O 3 particles in the composite Coatings could effectively hinder crack propagation via the formation of micro-cracks inside the Al 2 O 3 particles, which absorbs the impact energy. FEM indicates that the Al 2 O 3 dispersion acts as the main loading-bearing phase and alleviates the stress concentration in the composite Coating, thus suppresses crack initiation and propagation. Furthermore, electrochemical polarization test shows that composite Coating remains good corrosion resistance in a 3.5% NaCl solution after impact.
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Corrosion and wear resistance of a Fe-based Amorphous Coating in underground environment
Intermetallics, 2012Co-Authors: Ruiqiang Guo, Yudong Peng, Cheng Zhang, Ying Yang, Lin LiuAbstract:Fe-based Amorphous Coating with composition of Fe49.7Cr18Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 has been prepared on a mild steel substrate by High velocity air fuel (HVAF) process. Microstructural characterization showed that the Coating exhibits very dense structure with a porosity of 0.4% and compact bonding with the substrate. Polarization tests indicated that the Coating presents superior corrosion resistance in simulated groundwater; EIS measurements revealed that although the solution penetrated into the Coating defects, the corrosion process could slow down due to the plugging of the defects by corrosion products. It was also found that the Coating possesses good dry wear resistance and fatigue wear mechanism dominated the friction process. The present results imply that the Fe-based Amorphous Coating is promising for industry applications in underground environment, such as the storage of spent nuclear fuels.
Minghai Liu - One of the best experts on this subject based on the ideXlab platform.
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Effect of sol-gel sealing treatment loaded with different cerium salts on the corrosion resistance of Fe-based Amorphous Coating
Surface and Coatings Technology, 2019Co-Authors: Minghai Liu, Jinxiu Wang, Yunpu Zheng, Z.h. Gan, S. QiuAbstract:Abstract Porosity defects inevitably formed in the preparation of high-velocity oxy-fuel (HVOF)-sprayed Fe-based Amorphous Coating, which greatly affected the corrosion resistance and service lives of Fe-based Amorphous Coating. Sealing treatment could be an effective candidate method to alleviate the problem above. In this paper, three sealed Coatings including sol-gel (SG) Coating, sol-gel with cerium nitrate (SCN) Coating and sol-gel with cerium tartrate (SCT) Coating were applied on Fe-based Amorphous Coating. The influence of sealing treatment on the structure and corrosion resistance of Fe-based Amorphous Coating was investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and electrochemical methods. The results revealed the corrosion resistance of Fe-based Amorphous Coating was enhanced after sealing treatments in comparison with that of unsealed Coating. However, the density of SCN Coating was reduced compared with that of SG Coating, although it had corrosion inhibition effect. SCT Coating exhibited the best in eliminating defects and enhancing the corrosion resistance among three sealed Coatings. Moreover, the combined protection mechanism of SCT Coating was proposed and discussed.
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effects of three sealing methods of aluminum phosphate sealant on corrosion resistance of the fe based Amorphous Coating
Surface & Coatings Technology, 2017Co-Authors: Minghai Liu, Y G ZhengAbstract:Abstract Porosity defects inevitably existed in the high-velocity oxy-fuel (HVOF)-sprayed Fe-based Amorphous Coatings, which directly affected the service lives of the Coatings. Thus, sealing treatment became a key method to improve the Coatings' corrosion resistance and prolong their service lives. In this study, three sealing technologies including conventional impregnation sealing (CIS), ultrasonic excitation sealing (UES) and vacuum sealing (VS) were employed to seal the HVOF-sprayed Fe-based Amorphous Coatings with aluminum phosphate. The sealing effect and corrosion behaviour of these Coatings were investigated by scanning electron microscopy (SEM), electron probe micro-analyzer (EPMA) and electrochemical techniques. The results revealed that the aluminum phosphate sealant could block the structural defects of the Coatings by forming a barrier layer which consisted of Al(PO 3 ) 3 , H 2 (AlP 3 O 10 )·H 2 O, Al 2 P 6 O 18 and AlPO 4 , independent of the sealing methods. The impedance values increased by one or two orders of magnitude compared with that of the unsealed Coating indicating better corrosion resistance of the sealed Coatings. Moreover, based on the long-term corrosion tests of the three sealed Coatings, UES was the optimum sealing method. It was because that large amount of sealant was promoted to permeate into smaller cracks and holes and close the internal pores by ultrasonic energy.
Huamin Zhou - One of the best experts on this subject based on the ideXlab platform.
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on the bonding strength in thermally sprayed fe based Amorphous Coatings
Surface & Coatings Technology, 2013Co-Authors: Yudong Peng, Cheng Zhang, Huamin ZhouAbstract:Abstract Bonding strength is one of the most important properties in thermally sprayed Coatings as it plays crucial roles in the performance and lifetime of the Coatings. This study aims to explore different factors that affect the bonding strength of the Fe48Mo14Cr15Y2C15B6 Amorphous Coating prepared by high velocity oxygen fuel (HVOF) thermal spraying. The results demonstrate that the substrate roughness and the Coating thickness have significant influence on the bonding strength of the Amorphous Coating, e.g. the bonding strength increases when the substrate roughness is above a certain threshold, and decreases with the increasing Coating thickness. In addition, the bond strength can be effectively enhanced via the addition of an intermediate NiCrAl layer between the substrate and the Amorphous Coating due to the occurrence of metallurgical reaction and the improved interfacial structure. Finally, the fracture mechanism of the Coatings was also discussed.
Bin Liu - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of Amorphous Coating by laser cladding multi-layer Co-based self-fluxed alloy powder
Materials Letters, 2016Co-Authors: Fengyuan Shu, Wenxiong He, Shaohua Sui, Hongyun Zhao, Ze Tian, Bin LiuAbstract:An Amorphous Coating was synthesized on low carbon steel by laser cladding Co-based self-fluxed alloy powder successfully. The microstructure, thermal stability property of the fabricated Amorphous Coating was investigated. The thickness of Amorphous Coating was 400 µm while the dendrite zone was only 10 µm height near the interface. The volume fraction of Amorphous was 85.1% approximately. DSC curve showed that the glass transition temperature and the crystallization temperature were 298 °C and 342 °C, respectively. The supercooling liquid region was 44 °C which ensured the high thermal stability of Amorphous Coating against crystallization.
