The Experts below are selected from a list of 7752 Experts worldwide ranked by ideXlab platform
Soon-young Hwang - One of the best experts on this subject based on the ideXlab platform.
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superhard nano wc 12 co coating by Cold Spray deposition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Hyungjun Kim, Changhee Lee, Soon-young HwangAbstract: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.
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Superhard nano WC–12%Co coating by Cold Spray deposition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Hyungjun Kim, Changhee Lee, Soon-young HwangAbstract: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.
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Fabrication of WC–Co coatings by Cold Spray deposition
Surface & Coatings Technology, 2004Co-Authors: Hyungjun Kim, Changhee Lee, Soon-young HwangAbstract:Abstract Processing of cermet such as WC–Co is not easy by Cold (gas dynamic) Spraying although Cold Spray process can eliminate the degradation of the phase as compared to conventional high velocity oxy-fuel (HVOF) Spraying process. In this study, WC–12∼17%Co powders with nano- and microstructures were deposited by Cold Spray process using nitrogen and helium gases. Microstructural characterization and phase analysis of feedstock powders and as-deposited coatings were carried out by SEM and X-ray diffraction (XRD). The results show that there is no detrimental phase transformation and/or decarburization of WC by Cold Spray deposition as expected. It is also observed that nano-sized WC in the feedstock powder is maintained in the Cold Sprayed coatings. It seems that nano-sized WC is advantageous over micro-sized WC for Cold Spray deposition because higher particle velocity can be obtained with the same gas velocity. It is demonstrated that it is possible to fabricate the nano-structured WC–Co coating with low porosity and very high hardness (∼2050 HV) by Cold Spray deposition with reasonable powder preheating.
Hyungjun Kim - One of the best experts on this subject based on the ideXlab platform.
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superhard nano wc 12 co coating by Cold Spray deposition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Hyungjun Kim, Changhee Lee, Soon-young HwangAbstract: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.
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Superhard nano WC–12%Co coating by Cold Spray deposition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Hyungjun Kim, Changhee Lee, Soon-young HwangAbstract: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.
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Fabrication of WC–Co coatings by Cold Spray deposition
Surface & Coatings Technology, 2004Co-Authors: Hyungjun Kim, Changhee Lee, Soon-young HwangAbstract:Abstract Processing of cermet such as WC–Co is not easy by Cold (gas dynamic) Spraying although Cold Spray process can eliminate the degradation of the phase as compared to conventional high velocity oxy-fuel (HVOF) Spraying process. In this study, WC–12∼17%Co powders with nano- and microstructures were deposited by Cold Spray process using nitrogen and helium gases. Microstructural characterization and phase analysis of feedstock powders and as-deposited coatings were carried out by SEM and X-ray diffraction (XRD). The results show that there is no detrimental phase transformation and/or decarburization of WC by Cold Spray deposition as expected. It is also observed that nano-sized WC in the feedstock powder is maintained in the Cold Sprayed coatings. It seems that nano-sized WC is advantageous over micro-sized WC for Cold Spray deposition because higher particle velocity can be obtained with the same gas velocity. It is demonstrated that it is possible to fabricate the nano-structured WC–Co coating with low porosity and very high hardness (∼2050 HV) by Cold Spray deposition with reasonable powder preheating.
Changhee Lee - One of the best experts on this subject based on the ideXlab platform.
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superhard nano wc 12 co coating by Cold Spray deposition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Hyungjun Kim, Changhee Lee, Soon-young HwangAbstract: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.
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Superhard nano WC–12%Co coating by Cold Spray deposition
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Hyungjun Kim, Changhee Lee, Soon-young HwangAbstract: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.
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Fabrication of WC–Co coatings by Cold Spray deposition
Surface & Coatings Technology, 2004Co-Authors: Hyungjun Kim, Changhee Lee, Soon-young HwangAbstract:Abstract Processing of cermet such as WC–Co is not easy by Cold (gas dynamic) Spraying although Cold Spray process can eliminate the degradation of the phase as compared to conventional high velocity oxy-fuel (HVOF) Spraying process. In this study, WC–12∼17%Co powders with nano- and microstructures were deposited by Cold Spray process using nitrogen and helium gases. Microstructural characterization and phase analysis of feedstock powders and as-deposited coatings were carried out by SEM and X-ray diffraction (XRD). The results show that there is no detrimental phase transformation and/or decarburization of WC by Cold Spray deposition as expected. It is also observed that nano-sized WC in the feedstock powder is maintained in the Cold Sprayed coatings. It seems that nano-sized WC is advantageous over micro-sized WC for Cold Spray deposition because higher particle velocity can be obtained with the same gas velocity. It is demonstrated that it is possible to fabricate the nano-structured WC–Co coating with low porosity and very high hardness (∼2050 HV) by Cold Spray deposition with reasonable powder preheating.
Mahnaz Jahedi - One of the best experts on this subject based on the ideXlab platform.
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Development of 3D Multicomponent Model for Cold Spray Process Using Nitrogen and Air
Coatings, 2015Co-Authors: Muhammad Faizan Ur Rab, Seyed Hamid Zahiri, Mahnaz Jahedi, S. H. Masood, Romesh NagarajahAbstract:Cold Spray is a unique coating technology that allows for solid state deposition of particles under atmospheric pressure. In this paper, a three dimensional, Computational Fluid Dynamics (CFD) multicomponent model is developed to estimate Cold Spray gas conditions involving both nitrogen and air. Calibration of the model followed by validation is accomplished by considering the thermal history of substrate exposed to Cold Spray supersonic jet. The developed holistic multicomponent model is effective in determining the state of gas and particles from injection point to the substrate surface with the advantage of optimizing very rapid Cold Spray deposition in nanoseconds. The validation of k-e type CFD multicomponent model is done by using the temperature measured for a titanium substrate exposed to Cold Spray nitrogen at 800 °C and 3 MPa. Heat transfer and radiation are considered for the de Laval nozzle used in Cold Spray experiments. The calibrated multicomponent model has successfully estimated the state of propellant gas for the chosen high pressure and high temperature Cold Spray conditions. Moreover, the multicomponent model predictions are in good agreement with a previous holistic three dimensional Cold Spray model in which only nitrogen was used as the surrounding as well as the propellant gas.
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Development of Holistic Three-Dimensional Models for Cold Spray Supersonic Jet
Journal of Thermal Spray Technology, 2014Co-Authors: Seyed Hamid Zahiri, T. D. Phan, S. H. Masood, Mahnaz JahediAbstract:A three-dimensional, computational fluid dynamics (CFD) model is developed to estimate Cold Spray gas conditions. This model is calibrated and validated with respect to thermal history of a substrate exposed to the Cold Spray supersonic jet. The proposed holistic model is important to track state of gas and particles from injection point to the substrate surface with significant benefits for optimization of very rapid "nanoseconds" Cold Spray deposition. The three-dimensional model is developed with careful attention with respect to computation time to benefit broader Cold Spray industry with limited access to supercomputers. The k -ε-type CFD model is evaluated using measured temperature for a titanium substrate exposed to Cold Spray nitrogen at 800 °C and 3 MPa. The model important parameters are detailed including domain meshing method with turbulence, and dissipation coefficients during Spraying. Heat transfer and radiation are considered for the de Laval nozzle used in experiments. The calibrated holistic model successfully estimated state of the gas for chosen high temperature and high pressure Cold Spray parameters used in this study. Further to this, the holistic model predictions with respect to the substrate maximum temperature had a good agreement with earlier findings in the literature.
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Characterisation of Cold Spray Titanium Coatings
Materials Science Forum, 2010Co-Authors: Stefan Gulizia, Peter C. King, Mahnaz Jahedi, Andrea Trentin, Simone Vezzù, Silvano Rech, Mario GuaglianoAbstract:Cold Spray is a solid state Spray deposition process utilizing a supersonic De Laval nozzle to accelerate fine particles to high velocities. Particles plastically deform on impact to the substrate and to each other to create dense well adhered structures. In this study, the microstructure and mechanical properties of Cold Spray Titanium coatings deposited using nitrogen gas at different gas temperature and pressure were examined. In general, it was found that gas-atomised CP-titanium powder is capable of producing dense coating structures on aluminium alloy (Al6061) substrates. The micro-hardness, oxygen and nitrogen content of the coatings were found to be slightly higher than powder in the as-received condition. It was also found the coating residual stress was purely compressive when Cold Spray is conducted at high gas pressure and temperature.
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Aluminium coating of lead zirconate titanate—A study of Cold Spray variables
Surface and Coatings Technology, 2010Co-Authors: Peter C. King, Seyed Hamid Zahiri, Mahnaz Jahedi, James FriendAbstract:Cold Spray was used to deposit conductive aluminium coatings onto lead zirconate titanate (PZT) piezoceramics. The optimisation of processing parameters was explored. Grain removal from the PZT surface due to the impact of Al particles was reduced by increasing the average particle velocity. Surface domain reorientation was detected by X-ray diffraction (XRD). Substrate temperatures during Spraying were maintained at a low level by controlling the upstream, Cold Spray temperature and robot movement. The electrical resistance of the Cold Sprayed aluminium was 9.9 ± 0.5 μΩ cm. The impedance characteristics of poled specimens were shown to be unchanged by Cold Spray.
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Characterization of Cold Spray titanium supersonic jet
Journal of Thermal Spray Technology, 2009Co-Authors: Seyed Hamid Zahiri, William Yang, Mahnaz JahediAbstract:Titanium is widely used in aerospace, highly corrosive environments, and implants due to unique properties such as high strength to weight ratio and excellent corrosion resistance. Cold gas dynamic Spray (Cold Spray) technology, in contrast to current fabrication technologies, has provided the potential for titanium to be utilized in broader industrial applications and at lower cost. Particle velocity is the most important parameter in the Cold Spray process that leads to successful deposition of titanium at supersonic speeds. In this study, particle image velocimetry (PIV) is utilized to characterize supersonic flow field for a commercially pure (CP) titanium powder. The results represent experimentally deter- mined velocity for titanium particles under supersonic conditions with respect to propellant gas, Spray temperature, and stagnation pressure. The high velocity flow region outside of the Cold Spray nozzle was significantly extended using helium. An increase in stagnation temperature results in a high velocity region close to the axis of the Cold Spray nozzle. In contrast, an increase in pressure expands the high velocity regions in the Cold Spray plume. The PIV that is a whole-flow-field process is a practical characterization technique for optimization of parameters and validation of the future models for the Cold Spray process.
Seyed Hamid Zahiri - One of the best experts on this subject based on the ideXlab platform.
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Development of 3D Multicomponent Model for Cold Spray Process Using Nitrogen and Air
Coatings, 2015Co-Authors: Muhammad Faizan Ur Rab, Seyed Hamid Zahiri, Mahnaz Jahedi, S. H. Masood, Romesh NagarajahAbstract:Cold Spray is a unique coating technology that allows for solid state deposition of particles under atmospheric pressure. In this paper, a three dimensional, Computational Fluid Dynamics (CFD) multicomponent model is developed to estimate Cold Spray gas conditions involving both nitrogen and air. Calibration of the model followed by validation is accomplished by considering the thermal history of substrate exposed to Cold Spray supersonic jet. The developed holistic multicomponent model is effective in determining the state of gas and particles from injection point to the substrate surface with the advantage of optimizing very rapid Cold Spray deposition in nanoseconds. The validation of k-e type CFD multicomponent model is done by using the temperature measured for a titanium substrate exposed to Cold Spray nitrogen at 800 °C and 3 MPa. Heat transfer and radiation are considered for the de Laval nozzle used in Cold Spray experiments. The calibrated multicomponent model has successfully estimated the state of propellant gas for the chosen high pressure and high temperature Cold Spray conditions. Moreover, the multicomponent model predictions are in good agreement with a previous holistic three dimensional Cold Spray model in which only nitrogen was used as the surrounding as well as the propellant gas.
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Development of Holistic Three-Dimensional Models for Cold Spray Supersonic Jet
Journal of Thermal Spray Technology, 2014Co-Authors: Seyed Hamid Zahiri, T. D. Phan, S. H. Masood, Mahnaz JahediAbstract:A three-dimensional, computational fluid dynamics (CFD) model is developed to estimate Cold Spray gas conditions. This model is calibrated and validated with respect to thermal history of a substrate exposed to the Cold Spray supersonic jet. The proposed holistic model is important to track state of gas and particles from injection point to the substrate surface with significant benefits for optimization of very rapid "nanoseconds" Cold Spray deposition. The three-dimensional model is developed with careful attention with respect to computation time to benefit broader Cold Spray industry with limited access to supercomputers. The k -ε-type CFD model is evaluated using measured temperature for a titanium substrate exposed to Cold Spray nitrogen at 800 °C and 3 MPa. The model important parameters are detailed including domain meshing method with turbulence, and dissipation coefficients during Spraying. Heat transfer and radiation are considered for the de Laval nozzle used in experiments. The calibrated holistic model successfully estimated state of the gas for chosen high temperature and high pressure Cold Spray parameters used in this study. Further to this, the holistic model predictions with respect to the substrate maximum temperature had a good agreement with earlier findings in the literature.
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Aluminium coating of lead zirconate titanate—A study of Cold Spray variables
Surface and Coatings Technology, 2010Co-Authors: Peter C. King, Seyed Hamid Zahiri, Mahnaz Jahedi, James FriendAbstract:Cold Spray was used to deposit conductive aluminium coatings onto lead zirconate titanate (PZT) piezoceramics. The optimisation of processing parameters was explored. Grain removal from the PZT surface due to the impact of Al particles was reduced by increasing the average particle velocity. Surface domain reorientation was detected by X-ray diffraction (XRD). Substrate temperatures during Spraying were maintained at a low level by controlling the upstream, Cold Spray temperature and robot movement. The electrical resistance of the Cold Sprayed aluminium was 9.9 ± 0.5 μΩ cm. The impedance characteristics of poled specimens were shown to be unchanged by Cold Spray.
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Characterization of Cold Spray titanium supersonic jet
Journal of Thermal Spray Technology, 2009Co-Authors: Seyed Hamid Zahiri, William Yang, Mahnaz JahediAbstract:Titanium is widely used in aerospace, highly corrosive environments, and implants due to unique properties such as high strength to weight ratio and excellent corrosion resistance. Cold gas dynamic Spray (Cold Spray) technology, in contrast to current fabrication technologies, has provided the potential for titanium to be utilized in broader industrial applications and at lower cost. Particle velocity is the most important parameter in the Cold Spray process that leads to successful deposition of titanium at supersonic speeds. In this study, particle image velocimetry (PIV) is utilized to characterize supersonic flow field for a commercially pure (CP) titanium powder. The results represent experimentally deter- mined velocity for titanium particles under supersonic conditions with respect to propellant gas, Spray temperature, and stagnation pressure. The high velocity flow region outside of the Cold Spray nozzle was significantly extended using helium. An increase in stagnation temperature results in a high velocity region close to the axis of the Cold Spray nozzle. In contrast, an increase in pressure expands the high velocity regions in the Cold Spray plume. The PIV that is a whole-flow-field process is a practical characterization technique for optimization of parameters and validation of the future models for the Cold Spray process.
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Recrystallization of Cold Spray-fabricated CP titanium structures
Journal of Thermal Spray Technology, 2009Co-Authors: Seyed Hamid Zahiri, Darren Fraser, Mahnaz JahediAbstract:Cold gas dynamic Spray (Cold Spray) is a promising rapid deposition technology in which particles deposit at supersonic velocities. The effect of isothermal annealing on recrystallization and mechanical properties of commercial purity (CP) titanium structures that were directly fabricated through Cold Spray deposition is studied. The optimized Cold Spray parameters led to a dense Cold Spray structure. Results show that annealing improves ductility of the Cold-Sprayed CP titanium structure. The mechanism for softening is the nucleation and growth of equiaxed grains, which include an ultrafine grain structure. A physical-based model for recrystallization of the Cold Spray CP titanium is proposed. The results show that recrystallization does not eliminate preferred orientation inherited from the Cold Spray material.