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Chang-jiu Li - One of the best experts on this subject based on the ideXlab platform.

  • deposition of fully dense al based coatings via in situ micro forging assisted Cold Spray for excellent corrosion protection of az31b magnesium alloy
    Journal of Alloys and Compounds, 2019
    Co-Authors: Yi Ge, Guosheng Huang, Chang-jiu Li
    Abstract:

    Abstract In this work, three types of fully dense aluminum-based (Al) coatings (pure Al, AA2219 and AA6061) were deposited on AZ31B magnesium (Mg) alloy by a recently developed in-situ micro-forging assisted Cold Spray Process. The detailed microstructure, coating adhesion and corrosion protection performance were systematically investigated. Results show that the porosities of the pure Al, AA2219 and AA6061 coatings are as low as 0.34 ± 0.11%, 0.23 ± 0.09% and 0.24 ± 0.08%, respectively. Strong adhesion strength (83.6–91.5 MPa) was achieved for the Al-based coatings due to the in-situ micro-forging induced enhanced mechanical-interlocking between Al-based coating and the magnesium alloy substrate. The corrosion current density of the AZ31B Mg alloy decreases to 1.9–5.8 μA cm−2 from 312.8 μA cm−2 after coated with the Al-based coatings. The long-term corrosion tests further indicate that the Al-based coatings are not aqueous solution permeable during the entire 1000 h immersion, thus provided robust long-term corrosion protection of AZ31B Mg alloy substrate. Moreover, the difference in corrosion resistances among the three Al-based coatings was observed and was further explained based on their unique microstructures arising from the coating deposition Process. The present in-situ micro-forging assisted Cold Spray Process shows great potential for economical and effective corrosion protection of magnesium alloy and provides more freedom for industries to design and use magnesium alloy parts.

  • corrosion resistant nickel coating with strong adhesion on az31b magnesium alloy prepared by an in situ shot peening assisted Cold Spray
    Corrosion Science, 2018
    Co-Authors: Yu-juan Li, Yue Zhang, Chang-jiu Li
    Abstract:

    Abstract A 150 μm thick fully dense Ni coating was deposited on AZ31B magnesium alloy by a newly developed in-situ shot-peening-assisted Cold Spray Process. Strong adhesion strength of Ni coating (>65.4 MPa) was achieved. The present Ni coated AZ31B reveals comparable electrochemical behavior with annealed bulk Ni in 3.5 wt.% NaCl aqueous solution. Long-term immersion test (1000 h) and NaCl salt Spray test (1000 h) further verified the robust corrosion resistance of the Cold Sprayed Ni coating. This work provides a novel green approach for corrosion protection of magnesium alloys.

Hyung-jun Kim - One of the best experts on this subject based on the ideXlab platform.

  • numerical study of in flight particle parameters in low pressure Cold Spray Process
    Journal of Thermal Spray Technology, 2010
    Co-Authors: Xianjin Ning, Quansheng Wang, Hyung-jun Kim
    Abstract:

    A 2-D model of the low-pressure Cold Spray with a radial powder feeding was established using CFD software in this study. The flow field was simulated for both propellant gases of nitrogen and helium. To predict the in-flight particle velocity and temperature, discrete phase model was introduced to simulate the interaction of particle and the supersonic gas jet. The experimental velocity of copper powder with different sizes was used to validate the calculated one for low-pressure Cold Spray Process. The results show that the computational model can provide a satisfactory prediction of the supersonic gas flow, which is consistent with the experimental Schlieren photos. It was found that similar velocity was obtained with the drag coefficient formula of Henderson and with that of Morsi and Alexander. As the shape factor was estimated, the reasonable prediction of velocity for non-spherical particle can be obtained, to compare with the experimental results.

  • the effects of powder properties on in flight particle velocity and deposition Process during low pressure Cold Spray Process
    Applied Surface Science, 2007
    Co-Authors: Xianjin Ning, Jaehoon Jang, Hyung-jun Kim
    Abstract:

    In Cold Spray Process, impacting velocity and critical velocity of particles dominate the deposition Process and coating properties for given materials. The impacting velocity and critical velocity of particles depend on the powder properties and Cold Spray conditions. In the present study, the in-flight particle velocity of copper powder in low pressure Cold Spraying was measured using an imaging technique. The effects of particle size and particle morphology on in-flight particle velocity and deposition efficiency were investigated. The critical velocity of copper powder was estimated by combining the in-flight particle velocity and deposition efficiency. The effect of annealing of feedstock powder on deposition and critical velocity was also investigated. The results showed that the irregular shape particle presents higher in-flight velocity than the spherical shape particle under the same condition. For irregular shape particles, the in-flight velocity decreased from 390 to 282 m/s as the particle size increases from 20 to 60 μm. Critical velocities of about 425 m/s and more than 550 m/s were estimated for the feedstock copper powder with spherical and irregular shape morphology, respectively. For the irregular shape particles, the critical velocity decreased from more than 550 to 460 m/s after preheating at 390 °C for 1 h. It was also found that the larger size powder presents a lower critical velocity in this study.

  • study on metal diamond binary composite coatings by Cold Spray
    Materials Science Forum, 2007
    Co-Authors: Hyung-jun Kim, D. H. Jung, Jichan Jang, Chang Hee Lee
    Abstract:

    Metal/diamond binary composite coatings on Al substrate without grit blasting were deposited by Cold Spray Process with in-situ powder preheating. Microstructural characterization of the as-Sprayed coatings with different diamond size, strength and with/without Ti coating on diamond was carried out by OM and SEM. The assessment of basic properties such as tensile bond strength and hardness of the coatings, and the deposition efficiency was also carried out. Particular attention on the composite coatings was on the diamond fracture phenomenon during the Cold Spray deposition and the interface bonding between the diamond and the Fe-based metal matrix.

  • superhard nano wc 12 co coating by Cold Spray deposition
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005
    Co-Authors: Hyung-jun Kim, Chang Hee Lee, Soon-young Hwang
    Abstract:

    Abstract Processing of cermet such as WC–Co is not easy by Cold Spray deposition, although Cold Spray Process can eliminate the degradation of the WC phase as compared to conventional high velocity oxygen fuel (HVOF) or plasma Spraying Process. In this study, WC–12%Co powders with nano-sized WC were deposited by Cold Spray Process using helium gas. Microstructural characterization and phase analysis of feedstock powders and as-deposited coatings were carried out by SEM and XRD. The results show, as expected, that there is no detrimental phase transformation and/or decarburization of WC by Cold Spray deposition. It is also observed that nano-sized WC in the feedstock powder is maintained in the Cold Sprayed coatings. It is demonstrated that it is possible to fabricate the nano-structured WC–Co coatings with low porosity and very high hardness (∼2050 HV) by Cold Spray deposition with reasonable powder preheating.

  • Particle behavior in supersonic flow during the Cold Spray Process
    Metals and Materials International, 2005
    Co-Authors: Eui Hyuk Kwon, Jeong Whan Han, Chang Hee Lee, Sung Ho Cho, Hyung-jun Kim
    Abstract:

    The Cold Spray Process is a relatively new Process that uses high velocity metallic particles for surface modifications. Metallic powder particles are injected into a converging-diverging nozzle and accelerated to supersonic velocities. In this study two-dimensional temperature and velocitiy distributions of gas along the nozzle axis are calculated and the effects of gas pressure and temperature on particle velocities and temperature inside and outside the nozzle are investigated. It was found that acceleration of the gas velocity takes place in the area of the nozzle throat, and it increases and reaches a maximum value at the nozzle exit. Due to compression shocks, irregular changes of the gas jet properties were found in the area after the nozzle and these resulted in the experience of the maximum particle velocity by the change of the particle size at a given gas pressure and temperature.

W Oneill - One of the best experts on this subject based on the ideXlab platform.

  • the laser assisted Cold Spray Process and deposit characterisation
    Surface & Coatings Technology, 2009
    Co-Authors: M Bray, Andrew Cockburn, W Oneill
    Abstract:

    Abstract Laser-assisted Cold Spray (LCS) is a new coating and fabrication Process which combines the supersonic powder beam found in Cold Spray (CS) with laser heating of the deposition zone. LCS combines some advantages of CS: solid-state deposition, high build rate and the ability to deposit metals onto a range of substrates, with reduced operating costs which arise from not using a gas heater and replacing helium with nitrogen as the Process gas. A system has been developed to impact metallic powder particles onto a substrate which is locally heated using a diode laser. A pyrometer and control system are used to record and maintain impact site temperature. In this study, 50 µm powder particles are measured to be traveling at around 400 ms − 1 , and heated to temperatures between 450 °C and 900 °C when they impact the substrates. Build rates of up to 45 g min −  1 were achieved for deposits with less than 1% porosity. Oxygen and nitrogen content in the deposits were measured to be less than 0.6 wt.% and 0.03 wt.% respectively.

  • the laser assisted Cold Spray Process and deposit characterisation
    Surface & Coatings Technology, 2009
    Co-Authors: M Bray, Andrew Cockburn, W Oneill
    Abstract:

    Abstract Laser-assisted Cold Spray (LCS) is a new coating and fabrication Process which combines the supersonic powder beam found in Cold Spray (CS) with laser heating of the deposition zone. LCS combines some advantages of CS: solid-state deposition, high build rate and the ability to deposit metals onto a range of substrates, with reduced operating costs which arise from not using a gas heater and replacing helium with nitrogen as the Process gas. A system has been developed to impact metallic powder particles onto a substrate which is locally heated using a diode laser. A pyrometer and control system are used to record and maintain impact site temperature. In this study,

  • standoff distance and bow shock phenomena in the Cold Spray Process
    Surface & Coatings Technology, 2008
    Co-Authors: J. Pattison, S. Celotto, A Khan, W Oneill
    Abstract:

    Cold Spray involves the deposition of metallic powder particles using a supersonic gas jet. When the nozzle standoff distance is small, a bow shock is formed at the impingement zone between the supersonic jet and the substrate. It has long been thought that this bow shock is detrimental to Process performance as it can reduce particle impact velocities. By using computational fluid dynamics, Particle Image Velocimetry and Schlieren imaging it was possible to show that the bow shock has a negative influence on deposition efficiency as a result of a reduction in particle velocity. Furthermore, the existence of the bow shock was shown to be dependent on the length of the nozzle's supersonic potential core. Experiments were carried out with aluminium, copper and titanium powders using a custom-made helium nozzle, operating at 2.0 MPa and 20 °C, and a commercial nitrogen nozzle operating at 3.0 MPa and 300 °C. In all cases, it was found that there is a direct relationship between standoff distance and deposition efficiency. At standoff distances less than 60 mm, the bow shock reduced deposition efficiencies by as much as 40%.

Kazuhiro Ogawa - One of the best experts on this subject based on the ideXlab platform.

  • Development and Characterization of Photocatalytic GaN Coatings by Cold Spray Process
    Journal of Thermal Spray Technology, 2021
    Co-Authors: Shaoyun Zhou, Kazuhiro Ogawa, Yuji Ichikawa, Chrystelle A. Bernard, Kesavan Ravi, Hiroki Saito, Shu Yin
    Abstract:

    For the first time, the low-pressure Cold Spray (LPCS) Process was used to manufacture gallium nitride (GaN) films to enhance its photocatalytic properties and decrease its manufacturing cost. The deposition behavior of the GaN powder on stainless steel substrates was investigated. Several specimens, with sparsely deposited agglomerated GaN particles, were prepared under different Spray conditions. Quantitative analysis of the evolution of the coverage area, deposited particle count, and average sectional area shows that, upon impact, agglomerated GaN particles disintegrate, leading to large deposition of small particles. By analyzing the cross-sectional area of the deposited particle, no discernible permanent deformation of the substrate was observed. In addition, x-ray diffraction analysis of the coatings and powder indicated that no phase transformation occurred during the Process. Based on Williamson–Hall analysis, the broader peaks of the coatings were mainly attributed to the distortions in the GaN lattice rather than changes in the crystallite size. At 400°C and 0.6 MPa, the deposition efficiency reached 5.3%, and the photocatalytic activities of the coating were about 33% (+9% compared to the powder). It is attributed to the higher specific surface area and roughness that the coatings exhibit after the breakage of the particles during the Cold Spray.

  • critical deposition condition of conicraly Cold Spray based on particle deformation behavior
    Journal of Thermal Spray Technology, 2017
    Co-Authors: Yuji Ichikawa, Kazuhiro Ogawa
    Abstract:

    Previous research has demonstrated deposition of MCrAlY coating via the Cold Spray Process; however, the deposition mechanism of Cold Spraying has not been clearly explained—only empirically described by impact velocity. The purpose of this study was to elucidate the critical deposit condition. Microscale experimental measurements of individual particle deposit dimensions were incorporated with numerical simulation to investigate particle deformation behavior. Dimensional parameters were determined from scanning electron microscopy analysis of focused ion beam-fabricated cross sections of deposited particles to describe the deposition threshold. From Johnson-Cook finite element method simulation results, there is a direct correlation between the dimensional parameters and the impact velocity. Therefore, the critical velocity can describe the deposition threshold. Moreover, the maximum equivalent plastic strain is also strongly dependent on the impact velocity. Thus, the threshold condition required for particle deposition can instead be represented by the equivalent plastic strain of the particle and substrate. For particle-substrate combinations of similar materials, the substrate is more difficult to deform. Thus, this study establishes that the dominant factor of particle deposition in the Cold Spray Process is the maximum equivalent plastic strain of the substrate, which occurs during impact and deformation.

  • effect of substrate surface oxide film thickness on deposition behavior and deposition efficiency in the Cold Spray Process
    Journal of Thermal Spray Technology, 2015
    Co-Authors: Yuji Ichikawa, Kazuhiro Ogawa
    Abstract:

    The mechanism of Cold Spray deposition is not yet completely understood. The impinging velocity and deformation behavior of the particles are believed to be critical deposition conditions. However, such substrate conditions as oxide-film thickness and mechanical properties may also affect Cold Spray deposition. In this study we investigated the effect of substrate conditions, especially oxide film thickness, on the deposition Process. The efficiency of deposition and the relationship between the impinging position of the particles and the number of particles deposited were investigated for two substrates coated with oxide films of different thickness; the particles were deposited sparsely on the substrates. Results showed that efficiency of deposition was lower for the oxide film with the greater thickness. Deposition tendency was also associated with impinging velocity, i.e., the critical velocity on which oxide film thickness depends; this is the reason for the different efficiency of deposition. An oxide film may inhibit deposition on a new surface. These results indicate that oxide film thickness has a substantial effect on the efficiency of deposition on the substrate. They also imply that creation of a newly-formed surface is important to the deposition Process.

  • multi walled carbon nanotube reinforced copper nanocomposite coating fabricated by low pressure Cold Spray Process
    Surface & Coatings Technology, 2012
    Co-Authors: Kenta Takagi, Keiko Kikuchi, Hansang Kwon, Kazuhiro Ogawa, Akira Kawasaki
    Abstract:

    Abstract Multi-walled carbon nanotube (MWCNT)-reinforced copper (Cu) nanocomposite coatings were successfully deposited on aluminum (Al) substrate by a Cold Spraying Process at a low pressure. The microstructure and the Raman spectrum of the low-pressure-Cold-Sprayed MWCNT–Cu nanocomposite coating showed that the MWCNTs maintained their tube structure in the Cu matrix, even though structural damage to the MWCNTs increased slightly. MWCNT–Cu nanocomposite-coated Al exhibits higher thermal diffusivity than pure-Cu-coated Al with a comparable hardness. The higher thermal diffusivity of the MWCNT–Cu coating could be explained by the dispersion of MWCNTs within the clean and closed CNT/Cu interfaces, which were achieved with the aid of compressive stress during the Cold Spraying.

  • Computational simulation of Cold Spray Process assisted by electrostatic force
    Powder Technology, 2008
    Co-Authors: Hidemasa Takana, Kazuhiro Ogawa, Tetsuo Shoji, Hideya Nishiyama
    Abstract:

    Abstract The integrated model of compressible thermofluid, splat formation and coating formation for the Cold Spray Process has been established. In-flight behavior of nano-micro particles and the interaction between the shock wave and the particles in a supersonic jet flow impinging onto the substrate and further effect of electrostatic force on the particle acceleration are clarified in detail by carrying out a real-time computational simulation. The optimal particle diameters for an impinging particle velocity exceeding critical velocity exist. Particles with the diameter of submicron interact with shock wave and particles are decelerated prior to the impact. However, the particles can be accelerated considerably by utilizing electrostatic forces even in the presence of unavoidable shock waves. Finally, based on the integrated model, the coating thickness in an electrostatic assisted Cold Spray Process is evaluated.

Ehsan Toyserkani - One of the best experts on this subject based on the ideXlab platform.

  • On the evolution of substrate's residual stress during Cold Spray Process: A parametric study
    Materials and Design, 2018
    Co-Authors: Bahareh Marzbanrad, Hamid Jahed, Ehsan Toyserkani
    Abstract:

    A comprehensive study was undertaken to determine the effects of carrier gas temperature, pressure, and nozzle speed on the residual stresses induced by Cold Spray coating of aluminum 7075 powder onto AZ31B-H24 magnesium substrate. Embedded Fiber Bragg Grating sensors and thermocouples were employed for simultaneous in-situ measurements of strain and temperature during Cold Spray Process. A statistical model was then developed based on the significance and interactions of the Cold Spray parameters on the residual stress field. This model demonstrated that the induced temperature is the most significant parameter to the final formation of residual stress. It is also shown that the peening effect plus the temperature resulted from the Cold Spray yields to the dynamic recrystallization of the substrate near the surface, and generates nano-size grains at the interface. This research validates that the final size of the refined grains and the level of induced residual stress depend heavily on the Process' thermal energy.