• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.236-237
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• 2006

Cold spraying is a fairly new coating technique, which within the last decade attracted serious attention of research groups and spray companies. As compared to thermal spraying, the low process temperatures in cold spraying result in unique coating properties, which promise new applications. Since particles impact with high kinetic energy in the solid state, new concepts to describe coating formation are requested to enable the full potential of this new technology. The present contribution gives a brief review of current models concerning bonding, supplying a description of the most influential spray parameters and consequences for new developments. With respect to spray forming by cold cold spraying, microstructures and thick, further machineable structures are presented.

• Journal of Welding and Joining
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• v.32 no.3
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• pp.43-52
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• 2014

Recent developing tendency of thermal spray for green automotive industry are studied by searching of NDSL, KIPRIS, ScienceDirect and so on. Spraying techniques such as plasma spray, microwave treatment, dry-ice blasting, HVOF thermal spray, cold spraying, aerosol deposition are introduced, further more spraying materials such as nano particles, intermetallic compound, TiAlN, TiC, Si-Al alloys are investigated.

• Journal of Sericultural and Entomological Science
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• v.39 no.1
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• pp.1-11
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• 1997

In relations to cold acclimation, experiment was carried out to understand the seasonal changes in reserve substances of the mulberry. The shoot barks and leaves of three mulberry varieties(Kaeryangppong, Shinilppong and Yongcheonppong) were sampled, after that their reserve substances were analyzed. The cold hardiness of mulberry was investigated by DTA(Differential Thermal Analysis) method. To increase cold hardiness, gibberellin(100 ppm), kinetin(100 ppm) and Jambi 8 were sprayed on the mulberry leaves. After spraying, falling of the leaves of Yongcheonppong occured earier than the other varities. After the first frost, all of treatments except gibberellin were entirely fallen. Growth regulator extended the leaves fallen. After spraying, water of the shoot barks was not showed difference in the content among the treatments, but amino acid, carbohydrate and soluble protein increased from September to October. Starch content of the shoot barks and leaves was maximum in October, but thereafter decreased during wintering stage. In Shinilppong, Jambi 8 spray increased cold hardiness by 1-2$^{\circ}C$ more than no spray. It was concluded that the cold hardiness of the mulberry in midwinter is closely related to the reserve substances with spraying Jambi 8 on the mulberry leaves.

• Journal of ILASS-Korea
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• v.13 no.4
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• pp.193-199
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• 2008

Spray coating is a versatile surface modification technology in which coating is built-up based on the successive deposition of micron-scaled particles. Depending on the coating materials, the coatings can meet the required mechanical properties, corrosion resistance, and other properties of base materials. Spraying processes are mainly classified into thermal and kinetic spraying according to their bonding mechanism and deposition characteristics. Specifically, thermal spraying process can be further classified into many categories based on the design and mechanism of the process, such as frame spraying, arc spraying, atmospheric plasma spraying (APS), and high velocity oxygen-fuel (HVOF) spraying, etc. Kinetic spraying or cold gas dynamic spraying is a newly emerging coating technique which is low-temperature and high-pressure coating process. In this paper, overall view of thermal and kinetic spray coating technologies is discussed in terms of fundamentals and industrial applications. The technological characteristics and bonding mechanism of each process are introduced. Deposition behavior and properties of technologically remarkable materials are reviewed. Furthermore, industrial applications of spray coating technology and its potentials are prospected.

• Journal of Welding and Joining
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• v.20 no.4
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• pp.459-466
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• 2002

• Journal of Powder Materials
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• v.19 no.5
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• pp.348-355
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• 2012

Cold spray deposition using Titanium powder was carried out to investigate the effects of powder morphology and powder preheating on the coating properties such as porosity and hardness. The in-flight particle velocity of Ti powder in cold spray process was directly measured using the PIV (particle image velocimetry) equipment. Two types of powders (spherical and irregular ones) were used to manufacture cold sprayed coating layer. The results showed that the irregular morphology particle appeared higher in-flight particle velocity than that of the spherical one under the same process condition. The coating layer using irregular morphology powder represented lower porosity level and higher hardness. Two different preheating conditions (no preheating and preheating at $500^{\circ}C$) were used in the process of cold spraying. The porosity decreased and the hardness increased by conducting preheating at $500^{\circ}C$. It was found that the coating properties using different preheating conditions were dependent not on the particle velocity but on the deformation temperature of particle. The deposition mechanism of particles in cold spray process was also discussed based on the experimental results of in flight-particle velocity.

• Korean Journal of Metals and Materials
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• v.46 no.5
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• pp.321-327
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• 2008

Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_6$) coating was produced by cold spraying as a new fabrication process. The microstructure and macroscopic properties of amorphous coating layer was investigated and compared with those of cold sprayed pure Cu coating. Amorphous powders were prepared by gas atomization and Al 6061 was used as the substrate plate. X-ray diffraction results showed that Cu based amorphous powder could be successfully deposited by cold spraying without any crystallization. The Cu based amorphous coating layer ($300{\sim}400{\mu}m$ thickness) contained 4.87% porosity. The hardness of Cu based amorphous coating represented $412.8H_v$, which was correspond to 68% of the hardness of injection casted bulk amorphous material. The wear resistance of Cu based amorphous coating was found to be three times higher than that of pure Cu coating. The 3-point bending test results showed that the adhesion strength of Cu based amorphous coating layer was higher than that pure Cu coating. It was also observed that hard Cu base amorphous particle could easily deform soft substrate by particle collisions and thus generated strong adhesion between coating and substrate. However, the amorphous coating layer unexpectedly represented lower corrosion resistance than pure Cu coating, which might be resulted from the higher content of porosity in the cold sprayed amorphous coating.

• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.221-230
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• 2011

The cold spray process is an emerging technology that utilizes high velocity metallic particles for surface coating. Metallic powder particles are injected into a converging-diverging de Laval nozzle and accelerated to a high velocity by a supersonic gas flow. The cold spray process normally uses a circular nozzle that has a rather narrow spraying range. To overcome this fault, a slit nozzle was considered in this study. The slit nozzle is anticipated to reduce the coating process time because it has a wider coating width than the circular nozzle. However, the slit nozzle can reduce the coating efficiency because it does not allow as much gas and particle velocity as the circular nozzle. To improve the coating efficiency of a slit nozzle, the shape of the slit nozzle was modified. And the results of gas flow and particle behaviour according to the nozzlers shape were compared by the a numerical analysis. As a results, as Expansion Ratio(ER) of 7.5 was found to be the most optimal condition for enhancing the spraying efficiency when the ER was changed by the variation of nozzle neck and exit size.

• Journal of Powder Materials
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• v.20 no.1
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• pp.24-32
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• 2013

The effect of carrier gases (He, $N_2$) on the properties of Ti coating layers were investigated to manufacture high-density Ti coating layers. Cold spray coating layers manufactured using He gas had denser and more homogenous structures than those using $N_2$ gas. The He gas coating layers showed porosity value of 0.02% and hardness value of Hv 229.1, indicating more excellent properties than the porosity and hardness of $N_2$ gas coating layers. Bond strengths were examined, and coating layers manufactured using He recorded a value of 74.3 MPa; those manufactured using $N_2$ gas had a value of 64.6 MPa. The aforementioned results were associated with the fact that, when coating layers were manufactured using He gas, the powder could be easily deposited because of its high particle impact velocity. When Ti coating layers were manufactured by the cold spray process, He carrier gas was more suitable than $N_2$ gas for manufacturing excellent coating layers.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.47-48
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• 2006

Oridinal thermal spray process has developed into two ways, namely, temperature dominated represented by plasma spraying, and velocity dominated represented by HVOF. It is common for both that the particle materials sprayed are basically in melted or half melted condition. New process has developed recently, that is, Cold Spray and Aerosol Deposition. Particle's heating is limited in CS lower than half of the material's melting point. Moreover, exactly no heating is loaded in AD process. Through the investigation on common feature for these three spraying processes, potential of new material process - Particle Deposition, PD - is considered and proposed.