• 제목/요약/키워드: HVOF

검색결과 101건 처리시간 0.035초

노즐 형상변화에 따른 HVOF 용사총에서의 유동특성에 관한 수치적 연구 (A Numerical Study on Flow Characteristics in HVOF Thermal Spray with Various Torch Shapes)

  • 백재상;김윤제
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2007년도 춘계학술대회B
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    • pp.3062-3067
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    • 2007
  • HVOF thermal spray guns are now being widely used to produce protective coatings, on the surfaces of engineering components. HVOF technology employs a combustion process to heat the gas flow and melt the coating materials which are particles of metals, alloys or cermets. Particle flow which is accelerated to high velocities and combustion gas stream are deposited on a substrate. In order to obtain good quality coatings, the analysis of torch design must be performed. The reason is that the design parameters of torch influence gas dynamic behaviors. In this study, numerical analysis is performed to predict the gas dynamic behaviors in a HVOF thermal spray gun with various torch shapes. The CFD model is used to deduce the effect of changes in nozzle geometry on gas dynamics. Using a commercial code, FLUENT which uses Finite Volume Method and SIMPLE algorithm, governing equations have been solved for the pressure, velocity and temperature distributions in the HVOF thermal spray torch.

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HVOF 용사법에 의해 제조된 WC계 합금 코팅층의 방식특성(I) - 산성용액에서의 분극특성 - (Anti-Corrosion Characteristics of WC-based Alloy Coatings Fabricated by HVOF Process - Polarization Characteristics in Acid Solution -)

  • 김태용;김영식
    • 동력기계공학회지
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    • 제18권4호
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    • pp.72-77
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    • 2014
  • The aim of this study to investigate polarization characteristics of WC-based alloy coatings fabricated by high velocity oxygen fuel(HVOF) process. The coatings were fabricated by HVOF process with WC-CrC-Ni, WC-Co-Cr, WC-Co composite powders. Corrosion tests were carried out using potentiostat/galvanostat at solution with pH 2 and pH 6. Corrosion potential(Ecorr) and corrosion current density(Icorr) could be analyzed from polarization curve. WC-Co-Cr coating showed more incorrodible characteristics than other coatings at solution pH 2. WC-CrC-Ni coating was more favorable anti-corrosion characteristics than other coatings at solution with pH 6.

고속가스플래임 용사법을 이용한 광촉매 $TiO_2$-생분해성 플라스틱 복합재료의 개발 (The Development of Functional Photocatalytic $TiO_2$-Biodegrdable Plastic Composite Material by HVOF Spraying)

  • 방희선;방한서
    • Journal of Welding and Joining
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    • 제24권5호
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    • pp.57-61
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    • 2006
  • For the production of functional $TiO_2$-biodegradable plastic (polybutylene succinate:PBS) composite material with photocayalytic activity, we attempted to prepare $TiO_2$ coatings on PBS substrate by HVOF and plasma spraying techniques under various conditions. The microstructures of coatings were characterized with SEM and XRD analysis, and the photocatalytic efficiency of coatings was evaluated by the photo degradation of gaseous acetaldehyde. The effects of primary particle size and spraying parameters on the formation behavior, photocatalytic performance of the coatings have been investigated. The results indicated that for both the HVOF sprayed $P_{200}$ and $P_{30}$ coatings, the high anatase ratio of 100% can be achieved regardless of fuel gas pressure. On the other hand, the HVOF sprayed $P_7$ coating exhibited a largely decreased anatase ratio (from 100% to 49.1%) with increasing the fuel gas pressure, which may be attributed to much higher susceptibility of heat for 7 nm agglomerated powder. HVOF sprayed $P_{200}$ and $P_{30}$ coatings show better performance as compared to that of plasma sprayed $P_{200}$ coatings owing to the higher anatase ratio. However, the HVOF sprayed $P_7$ coatings did not show the photocatalytic activity, which may result from the extremely small reaction surface area to the photocatalytic activity and low anatase ratio.

Effect of laser heat-treatment on microstructure and micro-hardness of HVOF-sprayed WC-CoCr coating

  • Zhang, Shi-Hong;Cho, Tong-Yul;Yoon, Jae-Hong;Fang, Wei;Joo, Yun-Kon;Song, Ki-Oh;Li, Ming-Xi
    • 한국표면공학회:학술대회논문집
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    • 한국표면공학회 2007년도 추계학술대회 논문집
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    • pp.138-139
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    • 2007
  • The microstructure and micro-hardness of high velocity oxygen fuel-sprayed (HVOF) WC-CoCr coatings are comparatively studied for both before and after laser heat-treatment (LT) of the coatings. The results indicate that compared to HVOF WC-CoCro coating, the laser treatment has eliminated the pores almost entirely providing a more homogeneous and densified microstructure. And the compact interface of the coating with substrate is achieved by laser treatment. The thickness of the coating has decreased from 300 ${\mu}m$ to 225 ${\mu}m$ As a result, the average porosity is five times higher in HVOF coating than in the coating by laser treatment. The laser treatment has produced a considerable increment in the hardness of the coating near surface whose average value increases from Hv0.2=1262.4 in the HVOF-sprayed coating to Hv0.2=1818.7 in the coatings treated with laser.

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LPPS용사법과 HVOF 용사법으로 제조된 CoNiCrAlY 코팅의 고온물성에 관한 연구 (A study on the high temperature properties of CoNiCrAlY coating fabricated by HVOF and LPPS process)

  • 강현욱;권현옥;송요승
    • 한국표면공학회지
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    • 제34권2호
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    • pp.161-168
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    • 2001
  • A Thermal Barrier Coating (TBC) can play an important role in protecting parts from harmful environments at high temperatures such as oxidation, corrosion, and wear in order to improve the efficiency of aircraft engines by lowering the surface temperature of the turbine blade. The TBC can increase the life span of the product and improve the operating properties. Therefore, in this study the mechanical and thermal properties of the TBC such as oxidation, fatigue and shock at high temperatures were evaluated. A samples of a bond coat (CoNiCrAlY) produced by the High Velocity Oxygen Fuel (HVOF) and Low Pressure Plasma Spray (LPPS) method were used. The thickness of the HVOF coating layer was approximately $450\mu\textrm{m}$ to 500$\mu\textrm{m}$ and the hardness number of the coating layer was between 350Hv and 400Hv. The thickness of the LPPS coating was about 350$\mu\textrm{m}$ to 400$\mu\textrm{m}$ and the hardness number of the coating was about 370Hv to 420Hv. The X-ray diffraction analysis showed that CoNiCrAlY coating layer of the HVOF and LPPS was composed of the $\beta$and ${\gamma}$phase. After the high temperature oxidation test, the oxide scale with about l0$\mu\textrm{m}$ to 20$\mu\textrm{m}$ thickness appeared at the coating surface on the Al-depleted zone was observed under the oxide scale layer.

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실링재 및 실링방법이 HVOF 용사된 CrC-NiCr 코팅의 내식성에 미치는 영향 (Effect of Sealing Materials and Parameters on the Corrosion Resistance of HVOF-Sprayed CrC-NiCr Coatings)

  • 정영훈;남욱희;변응선;강태일;강정윤
    • 한국표면공학회지
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    • 제47권6호
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    • pp.323-329
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    • 2014
  • Effects of sealant and sealing procedure on corrosion resistance of high velocity oxy-fuel (HVOF) sprayed coatings were studied. HVOF-sprayed CrC-20NiCr coatings were sealed using three commercial sealants based on phenolics and epoxy. Penetration depth of sealants, measured by fluorescent microscope technique, was between $19{\mu}m$ and $340{\mu}m$ depending on sealant, sealing condition or sealing procedure. It was found that sealing on rotation status was more effective than that on stationary specimen due to the Coriolis effect of fluid in pores of the coating. From the CASS results, corrosion resistance of properly sealed CrC-20NiCr coatings was equal to that of hexa-valent chromium plating.

HVOF 용사 코팅 공정 조건에 따른 코팅층의 기공도 예측 (Porosity Prediction of the Coating Layer Based on Process Conditions of HVOF Thermal Spray Coating)

  • 전준협;서남혁;이종재;손승배;이석재
    • 한국분말재료학회지
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    • 제28권6호
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    • pp.478-482
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    • 2021
  • The effect of the process conditions of high-velocity oxygen fuel (HVOF) thermal spray coating on the porosity of the coating layer is investigated. HVOF coating layers are formed by depositing amorphous FeMoCrBC powder. Oxygen pressure varies from 126 to 146 psi and kerosene pressure from 110 to 130 psi. The Microstructural analysis confirms its porosity. Data analysis is performed using experimental data. The oxygen pressure-kerosene pressure ratio is found to be a key contributor to the porosity. An empirical model is proposed using linear regression analysis. The proposed model is then validated using additional test data. We confirm that the oxygen pressure-kerosene pressure ratio exponentially increases porosity. We present a porosity prediction model relationship for the oxygen pressure-kerosene pressure ratio.

HVOF 용사 건의 이동속도가 WC-Co 코팅층의 두께 형성 및 표면 특성에 미치는 영향 (Effect of Gun Nozzle Movement Speed in HVOF Process on the properties of Coating Thickness and Surface)

  • 김기범;김갑배;정종민;김권후
    • 열처리공학회지
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    • 제35권5호
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    • pp.262-269
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    • 2022
  • In order to process materials such as engineering plastics, which are difficult to mold due to their high strength compared to conventional polymer materials, it is necessary to improve the hardness and strength of parts such as screws and barrels of injection equipment in extrusion system. High-velocity oxygen fuel (HVOF) process is well known for its contribution on enhancement of surface properties. Thus in this study, using the HVOF process, WC coating layers of different thicknesses were bonded to the surface of S30C substrate by controlling the movement speed of the spray nozzle and each property was evaluated to decide the optimization condition. Through the results, the thickness of WC coating layer increased from 0 to 200 ㎛ maximum, along with the decrement of nozzle movement speed and the surface hardness get increased. Especially, the coated layer with the thickness over 180 ㎛ under the nozzle speed 500 mm/s had high hardness than thinner layer. In addition, the amount of wear consumed per unit time was also significantly reduced due to the formation of the coating layer.

캐비테이션-에로젼 특성에 미치는 HVOF 용사조건의 영향 (Effect of spray parameters on cavitation erosion behavior of HVOF coating)

  • 변응선;유인준;이규환;박율민
    • 한국표면공학회:학술대회논문집
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    • 한국표면공학회 2009년도 추계학술대회 초록집
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    • pp.115-115
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    • 2009
  • 캐비테이션-에로젼은 침식부식과 유사한 형태의 침식에 의한 손상이다. 즉, 고속의 애체흐름에 노출된 금속 표면을 따라 압력변화에 의해서 생성된 기포들이 파괴되는 것과 관련하여 일어나는 표면손상의 한 형태이다. 본 연구에서는 캐비테이션-에로젼 손상을 억제하기 위하여 WC 서멧을 HVOF 용사하였으며, 캐비테이션-에로젼 특성에 미치는 용사조건의 영향에 중점을 비교분석하였다.

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분무건조법에 의한 용사용 WC-17%Co 복합분말제조 및 HVOF(High Velocity Oxy-Fuel) 용사특성 (Fabrication of WC-17%Co Composite Powder for Thermal Spray by Spray-Drying Method and HVOF Thermal Spray Characteristics)

  • 설동욱;김병희;임영우;정민석;서동수
    • Journal of Welding and Joining
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    • 제14권6호
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    • pp.101-108
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    • 1996
  • In this study, WC-l7wt% Co composite powder for thermal spray was fabricated by spray drying method. The agglomerated composite powder had spheroidal morphology and the particle size distribution was 20~60${\mu}{\textrm}{m}$. WC and Co were distributed homogeneously. However, the strength of the spray-dried agglomerate was low due to the pores within the agglomerate. Therefore, the spray-dried agglomerate was broken down during HVOF thermal spray and the microstructure was inhomogeneous with many pores within the coating layer. And the decomposition of WC to W and $W_{6}$ $C_{2.54}$ was accelerated. The strength and flowability of the agglomerate were greatly improved by sintering heat treatment(110$0^{\circ}C$, 1 hour, hi atmosphere), and then the coating layer showed dense and homogeneous microstructure with well-developed splats. The hardness of the coating layer was H $v_{300}$ = 1072.2.2.

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