• Title, Summary, Keyword: Atmospheric plasma spray

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Microstructural Evolution of Thick Tungsten Deposit Manufactured by Atmospheric Plasma Spray Forming Route (Plasma Spray Forming 공정에 의해 제조된 텅스텐 성형체의 미세조직 형성 거동)

  • Lim, Joo-Hyun;Baik, Kyeong-Ho
    • Journal of Korean Powder Metallurgy Institute
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    • v.16 no.6
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    • pp.403-409
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    • 2009
  • Plasma spray forming is recently explored as a near-net-shape fabrication route for ultra-high temperature metals and ceramics. In this study, monolithic tungsten has been produced using an atmospheric plasma spray forming and subsequent high temperature sintering. The spray-formed tungsten preform from different processing parameters has been evaluated in terms of metallurgical aspects, such as density, oxygen content and hardness. A well-defined lamellae structure was formed in the as-sprayed deposit by spreading of completely molten droplets, with incorporating small amounts of unmelted/partially-melted particles. Plasma sprayed tungsten deposit had 84-87% theoretical density and 0.2-0.3 wt.% oxygen content. Subsequent sintering at 2500$^{\circ}C$ promoted the formation of equiaxed grain structure and the production of dense preform up to 98% theoretical density.

Fabrication and Characterization of Zirconia Thermal Barrier Coatings by Spray Drying and Atmospheric Plasma Spraying (분무건조 및 대기 플라즈마 용사에 의한 지르코니아 열차폐 코팅재의 제조 및 평가)

  • Kim, Chul;Heo, Yong Suk;Kim, Tae Woo;Lee, Kee Sung
    • Journal of the Korean Ceramic Society
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    • v.50 no.5
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    • pp.326-332
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    • 2013
  • In this study, we prepared yttria stabilized zirconia granules for thermal barrier coatings using a spray drying process. First, we characterized the properties of granules such as flow rate and packing density for utilizing the air plasma spray process. The flow rate and packing density data showed 0.732 g/sec and 2.14 $g/cm^3$, respectively, when we used larger and denser particles, which are better than hollow granules or smaller spherical granules. Second, we chose larger, spherical granules fabricated in alcohol solvent as starting powders and sprayed it on the bondcoat/nimonic alloy by an atmospheric plasma spray process varying the process parameters, the feeding rate, gun speed and spray distance. Finally, we evaluated representative thermal and mechanical characteristics. The thermal expansion coefficients of the coatings were $11{\sim}12.7{\times}10^{-6}/^{\circ}C$ and the indentation stress measured was 2.5 GPa at 0.15 of indentation strain.

Effect of the Raw Material and Coating Process Conditions on the Densification of 8 wt% Y2O3-ZrO2 Thermal Barrier Coating by Atmospheric Plasma Spray

  • Oh, Yoon-Suk;Kim, Seong-Won;Lee, Sung-Min;Kim, Hyung-Tae;Kim, Min-Sik;Moon, Heung-Soo
    • Journal of the Korean Ceramic Society
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    • v.53 no.6
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    • pp.628-634
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    • 2016
  • The 8 wt% yttria($Y_2O_3$) stabilized zirconia ($ZrO_2$), 8YSZ, a typical thermal barrier coating (TBC) for turbine systems, was fabricated under different starting powder conditions and coating parameters by atmospheric plasma spray (APS) coating process. Four different starting powders were prepared by conventional spray dry method with different additive and process parameter conditions. As a result, large- and small-size spherical-type particles and Donut-type particles were obtained. Dense structure of 8YSZ coating was produced when small size spherical-type or Donut-type particles were used. On the other hand, 8YSZ coating with a porous structure was formed from large-size spherical-type particles. Furthermore, a segmented coating structure with vertical cracks was observed after post heat treatment on the surface of dense structured coating by argon plasma flame at an appropriate gun distance and power condition.

Fabrication and Characterization of Environmental Barrier Coatings by Spray Drying and Atmospheric Plasma Spraying for Protection of Silicon Carbide Ceramics (분무건조 및 대기 플라즈마 용사에 의한 탄화규소 세라믹스용 내환경 코팅재의 제조 및 평가)

  • Feng, Fan Jie;Moon, Heung Soo;Kwak, Chan Won;Park, Ji Yeon;Lee, Kee Sung
    • Journal of the Korean Ceramic Society
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    • v.51 no.5
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    • pp.481-486
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    • 2014
  • Environmental barrier coatings (EBCs) are used to protect SiC-based ceramics or composites from oxidation and corrosion due to reaction with oxygen and water vapour at high temperatures above $1000^{\circ}C$. Mullite ceramics have been studied for environmental barrier coatings for Si-based ceramics. More recently, rare earth silicate ceramics have been identified as more water vapour-resistant materials than mullite for environmental barrier coatings. In this study, we fabricate mullite and yttrium silicate ceramics by an atmospheric plasma spray coating method using spherical granules fabricated by spray drying. As a result, EBCs with thicknesses in the range of $200-300{\mu}m$ are successfully fabricated without any macroscopic cracks or interfacial delamination. Phase and microstructure analysis are conducted, and the basic mechanical properties, such as hardness and indentation load-displacement curves are evaluated.

Microstructural Evolution of Aluminum Nitride - Yttrium Aluminum Garnet Composite Coatings by Plasma Spraying from Different Feedstock Powders (Aluminum Nitride - Yttrium Aluminum Garnet 분말 특성과 플라즈마 용사 코팅층의 미세조직)

  • So, Woong-Sub;Baik, Kyeong-Ho
    • Korean Journal of Materials Research
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    • v.21 no.2
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    • pp.106-110
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    • 2011
  • A high thermal conductive AlN composite coating is attractive in thermal management applications. In this study, AlN-YAG composite coatings were manufactured by atmospheric plasma spraying from two different powders: spray-dried and plasma-treated. The mixture of both AlN and YAG was first mechanically alloyed and then spray-dried to obtain an agglomerated powder. The spray-dried powder was primarily spherical in shape and composed of an agglomerate of primary particles. The decomposition of AlN was pronounced at elevated temperatures due to the porous nature of the spray-dried powder, and was completely eliminated in nitrogen environment. A highly spherical, dense AlN-YAG composite powder was synthesized by plasma alloying and spheroidization (PAS) in an inert gas environment. The AlN-YAG coatings consisted of irregular-shaped, crystalline AlN particles embedded in amorphous YAG phase, indicating solid deposition of AlN and liquid deposition of YAG. The PAS-processed powder produced a lower-porosity and higher-hardness AlN-YAG coating due to a greater degree of melting in the plasma jet, compared to that of the spray-dried powder. The amorphization of the YAG matrix was evidence of melting degree of feedstock powder in flight because a fully molten YAG droplet formed an amorphous phase during splat quenching.

Creation of Diamond/Molybdenum Composite Coating in Open Air

  • Ando, Yasutaka;Tobe, Shogo;Tahara, Hirokazu
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.1313-1314
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    • 2006
  • For improvement of wear resistance property of atmospheric thermal plasma sprayed molybdenum (Mo) coating, diamond deposition on the atmospheric plasma sprayed molybdenum coating by the combustion flame chemical vapor deposition (CFCVD) has been operated. In this study, to diminish the thermal damage of the substrate during operation, a thermal insulator was equipped between substrate and water-cooled substrate holder. Consequently, diamond particles could be created on the Mo coating without fracture and peeling off. From these results, it was found that this process had a high potential in order to improve wear resistance of thermal sprayed coating.

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Microstructure and Tribological Properties along with Chemical Composition and Size of Initial Powder in Fe-based BMG Coating through APS (대기 플라즈마 용사공정을 이용한 Fe계 벌크 비정질 금속 코팅의 초기 분말의 화학조성과 크기에 대한 미세 조직 및 마모 특성)

  • Kim, Jung-Hwan;Yoon, Sang-Hoon;Na, Hyun-Taek;Lee, Chang-Hee
    • Journal of the Korean institute of surface engineering
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    • v.41 no.5
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    • pp.220-225
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    • 2008
  • In this study, two kinds of Fe-based bulk metallic glasses (BMG) powder were built-up through atmospheric plasma spray (APS) technique. The microstructure of two coatings was analyzed through X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Crystallization and oxidation in coatings were affected by chemical composition and initial powder size. Then, both of them influenced the tribological property.

Tensile Analysis of Plasma Spray Coating Material by Classification of AE Signals (Acoustic Emission 파형분류에 의한 플라즈마 용사 코팅재의 인장해석)

  • ;;K. ONO
    • Journal of Ocean Engineering and Technology
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    • v.15 no.4
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    • pp.60-65
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    • 2001
  • Thermal spray coating is formed by a process in which melted particles flying with high speed towards substrate, then crash and spread on the substrate surface cooled and solidified in a very short time, Stacking of the particles makes coating. In this study, the exfoliation of $Al_2$O$_3$ and Ni-4.5wt.%Al thermally sprayed coating which were deposited by an atmospheric plasma spray apparatus are investigated using an AE method. A tensile test is conducted on notch specimens in a stress range below the elastic limit of substrate. The wave forms of AE generated from the three coating specimens can be classified by FFT analysis into two types which low frequency(type I waveform is considered to corresponds exfoliation of coating layers and type II waveform corresponds the plastic deformation of notch tip or the resultant fracture of coating. The fracture of the coating layers can estimate by AE event and amplitude, because AE features increase when the deformation generates.

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Photocatalytic Property of Nano-Structured TiO$_2$ Thermal Splayed Coating - Part I: TiO$_2$ Coating - (나노구조 TiO$_2$ 용사코팅의 미세조직 제어 공정기술 개발과 광촉매 특성평가 - Part I: TiO$_2$코팅 -)

  • 이창훈;최한신;이창희;김형준;신동우
    • Journal of Welding and Joining
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    • v.21 no.4
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    • pp.39-45
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    • 2003
  • Nano-TiO$_2$ photocatalytic coatings were deposited on the stainless steel 304(50$\times$70$\times$3mm) by the APS(Atmospheric Plasma Spraying). Photocatlytic reaction was tested in MB(methylene blue) aqueous solution. For applying nano-TiO$_2$ powders by thermal spray, the starting nano-TiO$_2$ powder with 100% anatase crystalline was agglomerated by spray drying. Plasma second gas(H$_2$) flow rate and spraying distance were used as principal process parameters which are known to control heat enthalpy(heat input). The relationship between process parameters and the characteristics of microstructure such as the anatase phase fraction and grain size of the TiO$_2$ coatings were investigated. The photo-decomposition efficiency of TiO$_2$ coatings was evaluated by the kinetics of MB aqueous solution decomposition. It was found that the TiO$_2$ coating with a lower heat input condition had a higher anatase fraction, smaller anatase grain size and a better photo-decomposition efficiency.