• 제목/요약/키워드: Cavitation-Erosion

검색결과 155건 처리시간 0.03초

Fe-20Cr-1Si-1C계 경면처리 합금의 cavitation erosion 저항성에 미치는 Mn 첨가의 영향 (Effect of Mn-Addition on the Cavitation Erosion Resistance of Surface-hardened Fe-20Cr-1Si-1C Aolly)

  • 김수철;박인호;장세기;김선진;강성군
    • 한국표면공학회지
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    • 제33권1호
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    • pp.10-16
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    • 2000
  • Characteristics of cavitation erosion resistance of Fe-20Cr-1Si-1C-xMn(x=0, 5, 15) alloys were investigated by SEM and XRD analysis. The effects on strain-induced transformations were considerably reduced with increasing the amounts of Mn due to twining that occurred at 5, 15Mn alloys, activating cavitation erosion rates(mg/$\textrm{cm}^2$) which varied as 0.055, 0.114 and 0.160mg/$\textrm{cm}^2$ for 0, 5, 15Mn. From the results, it was found that the addition of Mn element in Fe-base alloy provides more cracking sites at twins rather than absorbing strain energies, so accelerates cavitation erosion rates.

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Study on the Cavitation Damage of Cupronickel(70/30) Tube for Gas Absorption Refrigeration Machine

  • Lim, Uh-Joh;Jeong, Ki-Cheol;Yun, Byoung-Du
    • Journal of Advanced Marine Engineering and Technology
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    • 제28권2호
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    • pp.332-337
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    • 2004
  • The use of gas absorption refrigeration machine has considerably increased because of the shortage of the electric power in the summer and the regulation of freon refrigerant. Gas absorption refrigeration machine consists of a condenser, a heat exchanger. supplying pipes, a radiator etc, This system is likely to be corroded by acid. dissolved oxygen and gases, Cavitation erosion-corrosion by flow velocity of cooling water may happen in absorption refrigeration machine. In these cases. erosion and corrosion occur simultaneously. Then, it makes a serious damage with synergy effect. Therefore, this paper was studied on the cavitation damage of cupronickel(70/30) tube for gas absorption refrigeration machine, In the $30^{\circ}C$ tap water, linear polarization test and anodic polarization test were carried out for copper(C1220T-OL) and cupronickel(70/30) tube. Also, cavitation erosion-corrosion behavior of cupronickel (70/30) tube was considered, The main results are as following: (1) In the linear test, the corrosion current density of cupronickel(70/30) is higher than that of copper. (2) The erosion-corrosion rate of cupronickel(70/30) displayed later tendency than that of copper by vibratory cavitation in cooling water. (3) In cooling water, the progress mechanism of erosion-corrosion rate of copper and cupronickel(70/30) follows a pattern of incubation, acceleration, attenuation and a steady state period.

Examination of Cavitation-Induced Surface Erosion Pitting of a Mechanical Heart Valve Using a Solenoid-Actuated Apparatus

  • Lee, Hwan-Sung;Hwang, Sung-Won;Katsuyuki Yamamoto
    • Journal of Mechanical Science and Technology
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    • 제17권9호
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    • pp.1339-1348
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    • 2003
  • Several factors, including peak dp/dt of the ventricular pressure and maximum closing velocity of leaflet have been studied as indices of the cavitation threshold. In the present study, just before closing velocity of the leaflet has been studied as indices of the cavitation threshold, and cavitation erosion on the surface of a mechanical valve was examined by focusing on squeeze flow and the water hammer phenomenon during the closing period of the valve. A simple solenoid-actuated test device that can directly control the valve closing velocity was developed, and opening-closing tests of 3,000 and 40,000 cycles were performed at various closing velocities. There was a closing velocity threshold to occur erosion pitting of valve surface, and its value was about 0.4 m/s in this study. Cavitation-induced erosion pits were observed only in regions where squeeze flow occurred immediately before valve closure On the other hand, the number of the pits was found to be closely related to an area of water hammer-induced pressure wave below the critical pressure defined by water vapor pressure. Therefore, it was concluded that cavitation is initiated and augmented by the two pressure drops due to squeeze flow and water hammer phenomenon, respectively.

화염급냉 표면처리된 Cu-9Al-4.5Ni-4.5Fe 합금의 $\beta$' 마르텐사이트 형성에 의한 케비테이션 침식 저항성 향상에 관한 연구 (Improvement of the Resistance to Cavitation Erosion by the Formation of $\beta$' Martensite in Flame-Quenched Cu-9Al-4.5Ni-4.5Fe Alloys)

  • 홍성모;이민구;김광호;김경호;김흥회;홍순익
    • 한국표면공학회지
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    • 제37권4호
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    • pp.234-241
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    • 2004
  • Cavitation erosion properties of the Cu-9Al-4.5Ni-4.5Fe alloys (Al-bronze) surface-modified by flame quenching process have been investigated. After flame quenching at above $T_{\beta}$, the surfaces of Al-bronze with $\alpha$ + $\textsc{k}$ structure have been changed into the $\alpha$ + $\beta$' martensite phases by the eutectoid reaction of $\alpha$ + $\textsc{k}$\longrightarrow$\beta$ followed by the martensite transformation of $\beta$\longrightarrow$\beta$'. As a result of cavitation test, the measured incubation time and erosion rate of the $\alpha$ + $\beta$' alloy was 1.2 times higher and 1.5 times lower, respectively, compared to those of the conventional $\alpha$ + $\textsc{k}$ alloys, showing a remarkable increase of cavitation resistance with the formation of $\beta$' martensite. This is attributed to a preferential erosion of the $\textsc{k}$ precipitates that show the lowest resistance among the $\alpha$, $\textsc{k}$, $\beta$' phases under cavitation loading.ases under cavitation loading.

양극산화 후 실링처리된 알루미늄 합금의 해수 내 내식성과 캐비테이션 침식 저항성 평가 (Evaluation of Corrosion and Cavitation Erosion Resistance of Sealed Aluminum Alloy after Anodizing Treatment in Seawater)

  • 박일초;이정형;한민수;김성종
    • 한국표면공학회지
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    • 제51권2호
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    • pp.87-94
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    • 2018
  • Various sealing techniques were applied to the anodized 5083 aluminum alloy for marine environment to reduce corrosion and cavitation erosion damage. Electrochemical experiments and cavitation erosion tests were conducted to evaluate the corrosion resistance and cavitation resistance of the anodic oxide film treated with sealing in natural seawater solution. Then, damaged surface morphology was analyzed by scanning electron microscope(SEM) and 3D microscope. As the results of the electrochemical experiments, it was observed that the surface damage of all the experimental conditions in the anodic polarization experiment was locally grown by the combination of crack and corrosion damage. In the Tafel analysis, the corrosion resistance of all sealing treatment conditions was improved compared to the anodizing. On the other hand, cavitation erosion tests showed that the anodizing and all the sealing treatment conditions generated local pit damage by cavitation erosion attack and grew to crater damage in the observation of damaged surface by SEM. Also, the weight loss and the surface damage depth measured with the experiment time presented that most of the sealing treatment conditions showed better cavitation erosion resistance than the anodizing, and they had an incubation period at the beginning of the experiment.

해수환경중 캐비테이션 침식 -부식 하에서의 응력부식균열거동(I) (Stress Corrosion Cracking Behavior under Cavitation Erosion-Corrosion in Sea Water-Part (I))

  • 안석환;임우조
    • 수산해양기술연구
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    • 제36권2호
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    • pp.132-138
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    • 2000
  • The effect of fluid flow on corrosion and erosion-corrosion of metal is a well-recognized phenomenon in pipelines and machinery equipment, and so on. Not only are fluid hydrodynamics important, but also the corrosiveness of the process or production stream affects the corrosion system. Recent research demonstrates that it is possible to erosion-corrosion(E/C) phenomena in terms of hydrodynamics, electrochemical corrosion kinetics and film growth/removal phenomena. Stress corrosion cracking behavior under cavitation erosion-corrosion of mild steel(SS41) was investigated of base metal and weldment under loaded stress. Main result obtained are as follows : 1) The cavitation erosion sensitivity of base metal affected weight loss is more susceptive than heat affected zone, 2) The corrosion sensitivity affected weight loss of welding heat cycle is less susceptive on stress corrosion under cavitation erosion-corrosion than stress corrosion.

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Mn 첨가가 경면처리용 Fe계 신합금의 캐비테이션 에로젼과 슬라이딩 마모저항성에 미치는 영향 (Effect of Mn-Addition on the Sliding Wear Resistance and the Cavitation Erosion Resistance of Fe-base Hardfacing Alloy)

  • 김윤갑;오영민;김선진
    • 한국재료학회지
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    • 제12권7호
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    • pp.550-554
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    • 2002
  • The effect of Mn on cavitation erosion resistance and the sliding wear resistance of Fe-base hardfacing NewAlloy was investigated. Mn is known to decrease stacking fault energy and enhance the formation of $\varepsilon$-martensite. Cavitation erosion resistance for 50 hours and sliding wear resistance for 100 cycles were evaluated by weight loss. Fe-base hardfacing NewAlloy showed more excellent cavitation erosion resistance than Mn-added NewAlloys. $\Upsilon-\alpha$' phase transformation that can enhance erosion resistance by matrix hardening occurred in every specimens. But, only in Mn free Fe-base hardfacing NewAlloy, the hardened matrix could repress the propagation of cracks that was initialed at the matrix-carbides interfaces more effectively than Mn-added NewAlloy The Mn free Fe-base hardfacing NewAlloy showed better sliding wear resistance than Mn-added alloys. Mn-addition up to 5wt.% couldn't increase the sliding wear and cavitation erosion resistance of Fe-base hardfacing alloy because it didn't make $\Upsilon\to\varepsilon$ martensite phase transformation. Therefore, it is considered that the cavitation erosion and the sliding wear resistance can be improved due to $\Upsilon\to\varepsilon$ martensite phase transformation when Mn is added more than 5wt.% in Fe-base hardfacing alloys.

안정화 원소 Ti 첨가에 따른 스테인리스강의 해수 내 캐비테이션-침식 특성 (Cavitation-Erosion Characteristics of the Stainless Steel with Adding Ti Stabilizer Element in Sea Water)

  • 최용원;양예진;김성종
    • 한국표면공학회지
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    • 제49권4호
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    • pp.344-348
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    • 2016
  • Stainless steel is widely applied in many industrial fields due to its excellent anti-corrosion and durability characteristics. However, stainless steel is very vulnerable to cavitation attack caused by high speed flow of fluid in the chloride environments such as marine environment. These conditions promote intergranular corrosion and cavitation-erosion, leading to degradation of the structural integrity and service life. In order to prevent these problems, the stabilized stainless steel is applied to the offshore and shipbuilding industries. In this study, Ti was added to 19%Cr-9%Ni as the stabilizer element with different concentrations (0.26%, 0.71%), and their durabilities were evaluated with cavitation-erosion experiment by a modified ASTM G32 method. The microstructural change was observed with the stabilizer element contents. The result of the observation indicated that the amount of carbide precipitation was decreased and its size became finer with increasing Ti content. In the cavitation-erosion experiment, both weight loss and surface damage depth represented an inverse proportional relationship with the amount of Ti element. Consequently, the stainless steel containing 0.71% of Ti had excellent durability characteristics.

연강의 캐비테이션 침식-부식 특성에 관한 연구 ( 1 ) - 진동 캐비네이션 침식-부식 손상 거동 - (Study on the Characteristics of Cavitation Erosion-Corrosion for Mild Steel ( 1 ) - Damage Behaviour of Vibration Cavitation Erosion-Corrosion -)

  • 임우조;황재호
    • 수산해양기술연구
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    • 제31권4호
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    • pp.413-422
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    • 1995
  • 각종 환경 조건에서 진동 캐비테이션 침식-부식 시험 장치에 의해 연강(SS41)의 캐비테이션 침식-부식 손상 거동에 관한 연구를 한 결과 다음과 같은 결론을 얻었다. 1) 해수 중에서 캐비테이션 침식-부식 손상 거동은 중앙부와 테두리 부에서 거의 비슷한 정도로 발생하여 성장되지만, 증류수 중에서는 테두리부에서 손상이 먼저 발생한 다음 중앙부에도 손상이 점차 일어난다. 2) 비저항이 낮은 수도수 중의 캐비테이션 침식-부식 손상은 초기에는 비저항이 높은 증류수중에서의 것보다 증가하지만 시간이 경과하면서 CaCO 하(3)의 피막 형성에 의해 둔화된다. 3) 케비테이션 침식-부식 손상 특성은 잠복기, 증가기, 감소기 및 안정기의 4단계로 구분된다.

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내연기관용 슬라이드 베어링재의 케비테이션 침식거동과 부식영향 및 윤할유의 거동에 관한 연구 (A Study on the behaviour of Cavitation erosion and lubricating Oils and the influence of Corrosion on Slide Bearing Metals for Internal combustion Engine)

  • 이진열;임우조
    • 수산해양기술연구
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    • 제28권2호
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    • pp.171-183
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    • 1992
  • In this paper, the behaviour of cavitation erosion, influence of corrosion and corrosion control on slide bearing metals for internal combustion engine were investigated, and this experiment was done by the vibratory cavitation erosion tester. The main results obtained are as follows: 1. With decreasing the space between horn and specimen, the weight loss and its rate increased step by step. But the weight loss and its rate of 0.2mm space decreased conversely more than that of 0.4mm space at early stage. 2. The weight loss and its rate with change of pH were appeared to the order of pH2>pH12>pH7>pH4. And the weight loss and its rate at pH 4 decreased at best. 3. The weight loss and its rate by cavitation erosion for bearing metals were shown to the order of W.M7>W.M1>K.M4. 4. There appeared mainly small pit hole at pH2, and appeared the pit of netting thread type at pH12 by the results of the damaged surfaces at pH2 and pH12 environments that were sensitive to cavitation erosion. 5. With increasing the viscosity of lubricating oil, the weight loss rate by cavitation erosion became dull at the space below 0.5mm. 6. The protective efficiency of cavitation erosion-corrosion is superior inhibitor of chormate(25 ppm) to cathodic protection.

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