• Tribology and Lubricants
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• v.24 no.2
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• pp.96-103
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• 2008

PTFE is generally utilized as the form of composites with adding various fillers. The purpose of this paper lies on clarifying the friction and wear properties of the PTFE coating layer on steel. Especially, the effects of PTFE powder size for coating and surface roughness of the counter material on the properties are investigated. Sliding friction and wear tests are conducted at several sliding speeds by employing two types of PTFE coating layer using different powder sizes. One type of coating layer is composed of uniform fine powder, whereas the other type is made up of mixture powder of different sizes. As results, it is found that PTFE coating layer are effective to improve the wear resistance and to reduce the friction coefficient. It is clear that PTFE coating layers are abrasively removed by asperities of the counter material during sliding contact. However, PTFE coating layer with uniform fine powder shows somewhat better wear resistance than that with mixture powder of different sizes in low sliding speed region. It can be seen that the wear of the coating layer are drastically reduced because wear fragment from counter material are transferred to the coating layer. On the other hand, friction coefficient is shown not to be directly related with PTFE powder size in coating layer.

• Journal of Powder Materials
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• v.21 no.5
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• pp.349-354
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• 2014

This study is a basic research for repair material production which manufactured a Cu repair coating layer on the base material of a Cu plate using kinetic spray process. Furthermore, the manufactured material underwent an annealing heat treatment, and the changes of microstructure and macroscopic properties in the Cu repair coating layer and base material were examined. The powder feedstocks were sphere-shaped pure Cu powders with an average size of $27.7{\mu}m$. The produced repair coating material featured $600{\mu}m$ thickness and 0.8% porosity, and it had an identical ${\alpha}$-Cu single phase as the early powder. The produced Cu repair coating material and base material displayed extremely high adhesion characteristics that produced a boundary difficult to identify. Composition analysis confirmed that the impurities in the base material and repair coating material had no significant differences. Microstructure observation after a $500^{\circ}C/1hr$. heat treatment (vacuum condition) identified recovery, recrystallization and grain growth in the repair coating material and featured a more homogeneous microstructure. The hardness difference (${\Delta}H_v$) between the repair coating material and base material significantly reduced from 87 to 34 after undergoing heat treatment.

• Journal of Powder Materials
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• v.23 no.1
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• pp.8-14
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• 2016

A bulk-type Ta material is fabricated using the kinetic spray process and its microstructure and physical properties are investigated. Ta powder with an angular size in the range $9-37{\mu}m$ (purity 99.95%) is sprayed on a Cu plate to form a coating layer. As a result, ~7 mm-sized bulk-type high-density material capable of being used as a sputter material is fabricated. In order to assess the physical properties of the thick coating layer at different locations, the coating material is observed at three different locations (surface, center, and interface). Furthermore, a vacuum heat treatment is applied to the coating material to reduce the variation of physical properties at different locations of the coating material and improve the density. OM, Vickers hardness test, SEM, XRD, and EBSD are implemented for analyzing the microstructure and physical properties. The fabricated Ta coating material produces porosity of 0.11~0.12%, hardness of 311~327 Hv, and minor variations at different locations. In addition, a decrease in the porosity and hardness is observed at different locations upon heat treatment.

• Journal of Powder Materials
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• v.29 no.2
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• pp.123-131
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• 2022

The purpose of this study is to improve the mechanical properties and develop manufacturing technology through self-soluble alloy powder flame spray coating on the surface of a run-out table roller for hot rolling. The roller surface of the run-out table should maintain high hardness at high temperatures and possess high wear, corrosion, and heat resistances. In addition, sufficient bonding strength between the thermal spray coating layer and base material, which would prevent the peel-off of the coating layer, is also an important factor. In this study, the most suitable powder and process for roll manufacturing technology are determined through the initial selection of commercial alloy powder for roll manufacturing, hardness, component analysis, and bond strength analysis of the powder and thermal spray coating layer according to the powder.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.953-959
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• 2004

BaTiO$_3$ powder has been applied in so much electronic ceramics. Therefore, as recent, the method to add or coat additive will be needed BaTiO$_3$ powder. As a kind of the method, the coating of BaTiO$_3$ powder was considered. In this study, during BaTiO$_3$ powder was coated by BaTiO$_3$ sol, gelation path was experimented. Standard coating condition was set for homogeneous coating. The phase of the gel was deferent by gelation path. It was confirmed the amorphous gel was made in BaTiO$_3$ phase easily at low temperature. In the amorphous gel, particle growth was shown at 900$^{\circ}C$, because crystallization temperature was low. The optimal ratio of sol and powder was at 10 vol% for the homogeneous coating.

• Journal of Powder Materials
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• v.27 no.3
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• pp.210-218
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• 2020

A T-800 (Co-Mo-Cr) coating material is fabricated using Co-Mo-Cr powder feedstock and laser cladding. The microstructure and melted Al erosion properties of the laser-cladded T-800 coating material are investigated. The Al erosion properties of the HVOF-sprayed MoB-CoCr and bulk T-800 material are also examined and compared with the laser-cladded T-800 coating material. Co and lave phases (Co₂MoCr and Co₃Mo₂Si) are detected in both the laser-cladded T-800 coating and the bulk T-800 materials. However, the sizes of the lave phases are measured as 7.9 ㎛ and 60.6 ㎛ for the laser-cladded and bulk T-800 materials, respectively. After the Al erosion tests, the erosion layer thicknesses of the three materials are measured as 91.50 ㎛ (HVOF MoB-CoCr coating), 204.83 ㎛ (laser cladded T-800), and 226.33 ㎛ (bulk T-800). In the HVOF MoB-CoCr coating material, coarse cracks and delamination of the coating layer are observed. On the other hand, no cracks or local delamination of the coating layer are detected in the laser T-800 material even after the Al erosion test. Based on the above results, the authors discuss the appropriate material and process that could replace conventional bulk T-800 materials used as molten Al pots.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.687-689
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• 1995

Our team works on mixture of hard magnetic materials. As hard magnetic material we used mixture of powders: melt-spun ribbon Nd-Fe-B, ferrite and Alnico. Their different mixtures are basic material for dielectromagnets under our investigation. Main disadvantage of dielectromagnets with Nd-Fe-B alloy powder as a component is a low corrosion resistance. Protection against corrosion is covering dielectromagnets with metallic or organic coating film. The coating film protects dielectromagnets from free particles on the surface and low resistance for mechanical stresses too. The surface of dielectromagnets prepared from mixture of powders if formed by metallic particles - powder of Nd-Fe-B and Alnico, particles of oxide - powder of ferrite and particles of resin - bonding materials. Team work on technology of laying the metallic coating on dielectromagnets prepared from mixture of mentioned powders. Papers show the results of initial investigation on metallic coating technology. It shows influence of type and used technology of the metallic coating film on magnetic properties of dielectromagnets.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.596-596
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• 2006

• Clean Technology
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• v.12 no.1
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• pp.27-35
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• 2006

Main compositions of powder paint based on thermoset type epoxy resin consist of epoxy resin for powder coating, curing agent, filler and pigment. The curing system used in this study was based on diglycidyl ether of bisphenol-A (DGEBA) and dicyan diamide (DICY). The curing behavior and rheological properties of powder coating material were investigated using DSC and rheometer, respectively. And the adhesion strength between steel and powder coating material was measured using lap shear geometry. The optimum formulation of epoxy powder paint obtained from this study was base resin of 100 phr, DICY of 6 phr, $CaCO_3$ of 20 phr, and $TiO_2$ of 10 phr.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.339-339
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• 2007

Metal coating on ceramic powder has long been attracting interest for various applications such as superconductor where the brittle nature of high temperature ceramic superconductor was complemented by silver coating and metalloceramics where mechanical property improvement was achieved via electroless plating. More recently it has become of great interest in embedded passive device applications since metal coating on ceramic particles may result in the enhancement of the dielectric properties of ceramic-polymer composite capacitors. In our study, nickel ion-containing solution was used for coating commercial capacitor-grade $BaTiO_3$ powder. After filtering process, the powder was dried and heat-treated in 5% forming gas at $900^{\circ}C$. XRD and TEM were utilized for the observation of crystallization behavior and morphology of the particles. It was found that the nickel coating characteristics were strongly dependent on the several parameters and processing variables, such as starting $BaTiO_3$ particle size, nickel source, solution chemistry, coating temperature and time. In this paper, the effects of these variables on the coating characteristics will be presented in some detail.