• Title/Summary/Keyword: plasma spray

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Fabrication of Cr$_2$O$_3$/Mo Composite Powders and Tribological Properties of Plasma-sprayed Coatings (플라즈마 용사용 산화크롬/몰리브덴 복합분말 제조와 용사코팅의 마찰.마멸 특성)

  • 여인웅;안효석;김충현
    • Tribology and Lubricants
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    • v.15 no.2
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    • pp.184-192
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    • 1999
  • Various compositions of$ Cr_2$$O_3$/Mo composite powders were fabricated using spray-drying method and plasma-spray coatings of these powders were prepared to understand their tribological properties. Experiments were conducted using a reciprocal type tribo-tester at room temperature under dry sliding condition. The worn surface of coated specimens were observed using SEM (Scanning Electron Microscopy) and chemical compositions were analyzed using XRD (X-ray Diffractometry) and XPS (X-ray Photoelectron Spectroscopy). The results showed that friction coefficient of the Mo added specimens were lower than that of $Cr_2$$O_3$specimen. However $Cr_2$$O_3$specimen showed the lowest wear loss. Wear protecting layer were observed at the worn surface of coated specimens with Mo addition. From the XPS analysis, the mixed phases of $Cr_2$$O_3$ $CrO_3$and $MoO_3$were founded in the wear protecting layer.

Effect of Vacuum Heat Treatment on the Properties in Thermal Sprayed Ceramics Coating (세라믹스 용사 코팅 특성에 미치는 진공열처리의 영향)

  • Lee, J.I.;Ur, S.C.;Lee, Y.G.
    • Journal of the Korean Society for Heat Treatment
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    • v.13 no.2
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    • pp.98-102
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    • 2000
  • The effect of vacuum heat treatment in the thermal sprayed ceramics coating on a capstan by either high velocity oxygen fuel(HVOF) or plasma thermal spray process was investigated. The coating materials applied on the capstan were tungsten and chrome carbides. In order to characterize the interface between coating layer and bare materials, hardness, adhesion strength, X-ray diffraction(XRD) and microstructural analysis are conducted. The adhesion strength of the carbide coated materials by HVOF process is over 500MPa compared to those of plasma coating process is 230MPa. In case of the carbide coated materials by HVOF process, the adhesion strength is increased to 15MPa and the porosity is reduced under 5% by vacuum heat treatment for 5 hrs at $1000^{\circ}C$. The XRD results reveal that the increasement is believed due to the phase stabilization of metastable $Cr_3C_2$ phase to stable $Cr_{23}C_6$ phase.

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Experimental Study on the Corrosion Characteristics of Zn and Zn-15Al Coatings Deposited by Plasma Arc Thermal Spray Process in Saline Solution (플라즈마 아크 용사 공법에 의해 도포된 Zn 및 Zn-15Al 금속 코팅의 해수 환경에서 부식 특성에 관한 실험적 연구)

  • Jeong, Hwa-Rang;Lee, Han-Seung
    • Journal of the Korea Institute of Building Construction
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    • v.21 no.6
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    • pp.539-550
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    • 2021
  • In this study, Zn and Zn-15Al were coated on general carbon steel by plasma arc metal spraying and then immersed in a 3.5wt.% NaCl solution similar to the seawater environment to evaluate the corrosion resistance properties. Through the surface shape analysis test by SEM and XRD, it was found that the Zn coating was porous and needle-shaped, so the penetration of the electrolyte was easy, and thus the corrosion rate was rapid. On the other hand, the Zn-15Al coating had a uniform and dense shape and was shown to suppress corrosion.

Development Status of High Enthalpy Plasma Equipment (전북대 고온플라즈마 설비 구축 및 응용연구 소개)

  • Choi, Chea-Hong;Lee, Mi-Yun;Kim, Min-Ho;Hong, Bong-Guen;Seo, Jun-Ho
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.694-696
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    • 2011
  • The high enthalpy plasma research center in Chonbuk national university is under construction for four types of plasma equipments. The equipments are 1set of 0.4 MW class enhanced Huels type plasma equipment, 1 set of 2.4 MW class enhanced Huels type plasma quipment, 1 set of 60 kW RF plasma equipment and 1 set of 200 kW RF plasma equipment. 60kW RF plasma system is R&D and pilot scale production equipment of nano powder synthesis and plasma spray coating. 200kW RF plasma system is mass production equipment with high power capacity of nano powder synthesis. 0.4MW plasma system can be applied to the ground test facility for material testing under re-entry conditions for space vehicles.

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Thermoelectric Properties of p- type FeSi2 Processed by Mechanical Alloying and Plasma Thermal Spraying (기계적 합금화 p-type FeSi2의 플라즈마 용사 성형 및 열전 특성)

  • Choi Mun-Gwan;Ur Soon-Chul;Kim IL-Ho
    • Korean Journal of Materials Research
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    • v.14 no.3
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    • pp.218-223
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    • 2004
  • P-type $\beta$-FeSi$_2$ with a nominal composition of $Fe_{0.92}Mn_{0.08}Si_2$ powders has been produced by mechanical alloying process. As-milled powders were spray dried and consolidated by atmospheric plasma thermal spraying as a rapid sintering process. As-milled powders were of metastable state and fully transformed to $\beta$-$FeSi_2$ phase by subsequent isothermal annealing. However, as-thermal sprayed $Fe_{0.92}Mn_{0.08}Si_2$ consisted of untransformed mixture of $\alpha$-$Fe_2Si_{5}$ and $\varepsilon$-FeSi phases. Isothermal annealing has been carried out to induce transformation to the thermoelectric semiconducting $\beta$-$FeSi_2$ phase. Isothermal annealing at $845^{\circ}C$ in vacuum gradually led to the thermoelectric semiconducting $\beta$-$FeSi_2$ phase transformation, but some residual metallic $\alpha$ and $\varepsilon$ phases were unavoidable even after prolonged annealing. Thermoelectric properties of $\beta$-$FeSi_2$ materials before and after isothermal annealing were evaluated. Seebeck coefficient increased and electric conductivity decreased with increasing annealing time due to the phase transition from metallic phases to semiconducting phases. Thermoelectric properties showed gradual increment, but overall properties appeared to be inferior to those of vacuum hot pressed specimens.

HISTOLOGIC COMPARATIVE STUDY ON THE BONE-IMPLANT INTERFACE OF HYDROXYLAPATITE AND TITANIUM PLASMA SPRAY COATED IMPLANTS (Hydroxylapatite 및 Titanium Plasma Spray 피복임프란트와 골조직 계면의 조직학적 비교 연구)

  • Cho, Ju-Oh;Song, Kwang-Yeob;Park, Charm-Woon
    • The Journal of Korean Academy of Prosthodontics
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    • v.33 no.3
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    • pp.492-516
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    • 1995
  • This study evaluated the responses of mandibular bones of mongrel dogs to loaded hydro xylapatite(HA) and titanium plasma spray(TPS) coated endosseous dental implants, using unloaded ones as the control group. after HA and TPS coated implants were implanted, their bone reactions with vital bones have been observed with light and scanning electron microscope(SEM) at the three periods of the 4th, 12th and 20th week. These reactions have been also compared in a histomorphometric method. The elemental distribution state of implants and the interface neighboring bone tissues have been measured with the energy dispersive analysis of X-rays(EDAX). The following results were obtained ; 1. The light microscopic analysis showed osseointegration in both the control group and the occlusal force loaded group ; Its degree was shown to be higher in the long-maintained and occlusal force groups. 2. The SEM analysis showed that both groups had osseointegration, In the case of TPS-coated implants, the coated layer was divided on the bone interface. In the case of HA-coated implants, there appeared a division between the metal and coated interface. 3. In the histomorphometric analysis, the measured ratio contaction bone of TPS-coated implants was $70{\pm}19$% in the case of no occlusal force ; it was $84{\pm}13$% in the case of occlusal force. The measured ratio contacting bone of HA-coated implants was $75{\pm}18$% in the case of no occlusal force ; it was $94{\pm}9$% in the case of occlusal force. However, there was no significant difference statistically(p>0.05). 4. Both groups showed that the ratio of calcium and phosphorous increased more in the bone tissues than on the bone to implant interface.

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Dietary spray-dried plasma improves intestinal morphology of mated female mice under stress condition

  • Liu, Yanhong;Choe, Jeehwan;Kim, Sheena;Kim, Byeonghyeon;Campbell, Joy M.;Polo, Javier;Crenshaw, Joe D.;Pettigrew, James E.;Song, Minho
    • Journal of Animal Science and Technology
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    • v.60 no.6
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    • pp.10.1-10.6
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    • 2018
  • Background: Stress causes inflammation that impairs intestinal barrier function. Dietary spray-dried plasma (SDP) has recognized anti-inflammatory effects and improvement of gut barrier function. Therefore, the purpose of this study was to investigate the effects of dietary SDP on intestinal morphology of mated female mice under stress condition. Results: Villus height, width, and area of small intestines were low on gestation day (GD) 3 or 4 under stress conditions, and higher later (Time, P < 0.05). Crypt depth of colon was low on GD 4 and higher later (Time, P < 0.05). Meanwhile, the SDP treatments improved (P < 0.05) intestinal morphology, indicated by increased villus height, villus width, villus area, and ratio between villus height and crypt depth of small intestines and crypt depth of colon, and by decreased crypt depth of small intestines, compared with the control diet. The SDP treatments also increased (P < 0.05) the number of goblet cells in intestines compared with the control diet. There were no differences between different levels of SDP. Conclusion: Dietary SDP improves intestinal morphology of mated female mice under stress condition.

Preparation of Suspension in La2O3-Gd2O3-ZrO2 System via Planetary Mill and Characteristics of (La1-xGdx)2Zr2O7 Coatings Fabricated via Suspension Plasma Spray (유성구볼밀을 이용한 La2O3-Gd2O3-ZrO2 계 서스펜션준비와 서스펜션 플라즈마용사를 이용한 (La1-xGdx)2Zr2O7 코팅증착과 특성)

  • Kwon, Chang-Sup;Lee, Sung-Min;Oh, Yoon-Suk;Kim, Hyung-Tae;Jang, Byung-Koog;Kim, Seongwon
    • Journal of Powder Materials
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    • v.20 no.6
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    • pp.453-459
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    • 2013
  • Lanthanum/gadolinium zirconate coatings are deposited via suspension plasma spray with suspensions fabricated by a planetary mill and compared with hot-pressed samples via solid-state reaction. With increase in processing time of the planetary mill, the mean size and BET surface area change rapidly in the case of lanthanum oxide powder. By using suspensions of planetary-milled mixture between lanthanum or gadolinium oxide and nano zirconia, dense thick coatings with fully-developed pyrochlore phases are obtained. The possibilities of these SPS-prepared coatings for TBC application are also discussed.

Fabrication and Characteristics of Thermal Barrier Coatings in the La2O3-Gd2O3-ZrO2 System by Using Suspension Plasma Spray with Different Suspension Preparations (서스펜션의 준비방법에 따른 서스펜션 플라즈마 용사를 이용한 La2O3-Gd2O3-ZrO2 계 열차폐코팅의 제조와 특성)

  • Lee, Soyul;Lee, Sung-Min;Oh, Yoon-Suk;Kim, Hyung-Tae;Nahm, Sahn;Kim, Seongwon
    • Journal of the Korean institute of surface engineering
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    • v.49 no.6
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    • pp.595-603
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    • 2016
  • Rare-earth zirconates, including lanthanum zirconate and gadolinium zirconate, have been investigated as ones of the most promising candidates for next-generation thermal barrier coating (TBC) materials due to their excellent properties such as low thermal conductivity, chemical stability at high temperature and so on. In this study, TBCs with three compositions, in the $La_2O_3-Gd_2O_3-ZrO_2$ system with reduced rare-earth contents from $RE_2Zr_2O_7$ compositions, were fabricated by using suspension plasma spray with different suspension preparation methods. The phase formation, microstructure, and thermal properties of TBCs were examined. In particular, each coating exhibited single fluorite phase and a dense, vertically-separated microstructure. The potential of coatings with rare-earth zirconates for TBC applications was also discussed.

Fabrication and Characterization of 7.5 wt% Y2O3-ZrO2 Thermal Barrier Coatings Deposited by Suspension Plasma Spray (서스펜션 플라즈마 용사법을 이용한 7.5 wt% Y2O3-ZrO2 열차폐코팅 제조 및 평가)

  • Lee, Won-Jun;Oh, Yoon-Suk;Lee, Sung-Min;Kim, Hyung-Tae;Lim, Dae-Soon;Kim, Seongwon
    • Journal of the Korean Ceramic Society
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    • v.51 no.6
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    • pp.598-604
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    • 2014
  • Considerable research efforts have been explored attempting to enhance the thermal durability of thermal barrier coatings (TBCs) at the high operating temperatures of gas turbines. In this study, the suspension plasma spray (SPS) process was applied to produce TBCs with a segmented structure by using an yttria-stabilized zirconia (YSZ) suspension. Four different experiment sets were carried out by controlling the ratio between surface roughness of the bond coat and feed stock size ($R_a/D_{50}$) in order to examine the effect of $R_a/D_{50}$ ratio on the microstructure of SPS-prepared coatings. When the $R_a/D_{50}$ had a high value of 11.8, a deposited thick coating turned out to have a cone-type columnar microstructure. In contrast, at the low $R_a/D_{50}$ values of 2.9 and 0.18, a deposited thick coating appeared to have a dense, vertically-cracked microstructure. However, with the very low $R_a/D_{50}$ value of 0.05 the coating was delaminated.