• Journal of Advanced Marine Engineering and Technology
• /
• 제24권1호
• /
• pp.49-58
• /
• 2000

Thermal spraying is one of the most common surface coating techniques to be used for many applications and flame spraying covers a wide range of different materials which can be coated onto various substrates. The purpose of this study is to investigate the effects of mixed ratio in composite coatings on the mechanical and anti-corrosion properties. The five different types of composite coatings were made with $Al_2O_3$ ceramic and Ni-alloy powder on the mild steel substrate by flame spraying method. The mechanical properties such as microhardness, adhesive strength and erosion resistance and corrosion resistance were tested for the sprayed coating specimens. The results obtained are summarized as follows; 1. The composite coating layers greatly improve the microstructure, erosion resistance and adhesive strength by increasing the content of Ni-Al alloy. 2. Microhardness of the compsite coating layer is decreased by increasing the content of Ni-Al alloy. 3. The anti-corrosion properties is considerably improved by increasing the compsite rate of Ni-Al alloy.

• Corrosion Science and Technology
• /
• 제14권2호
• /
• pp.76-84
• /
• 2015

The components in ultra super critical (USC) steam turbine, which is under development for high efficient power generation, are encountering harsher solid particle erosion by iron oxide scales than ones in the existing steam turbines. Therefore, the currently used boride coating will not be able to hold effective protection from particle erosion in USC system and should be replaced by new particle erosion resistant coatings. One of the best protective coatings developed for USC steam turbine parts was found to be vanadium-boride (V-boride) coating which has a hardness of about 3000 HV, much higher than that of boride, 1600~2000 HV. In order to evaluate particle erosion resistance of the various coatings such as V-boride, boride and Cr-carbide coatings at high temperature, particle erosion test equipments were designed and manufactured. In addition, erosion particle velocity was simulated using FLUENT software based on semi-implicity method for pressure linked equations revised (SIMPLER). Based on experimental results of this work, the vanadium-boride coating was found to be superior to others and to be a candidate coating to replace the boride coating.

• 한국지반신소재학회논문집
• /
• 제14권2호
• /
• pp.71-79
• /
• 2015

기존의 비탈면녹화공법인 식생기반재취부공법은 결합력의 부족이나 건조화, 유기물의 부족 등의 문제점들을 보이고 있다. 특히 비산이 심한 지역의 비탈면은 식생피복율이 현저히 떨어지고 시간이 경과함에 고사율이 증가되어 피복율이 더 저하되고 또다시 침식 및 비산이 증가하는 악순환이 이루어지고 있는 상황이다. 따라서 본 연구에서는 침식이나 비산에 저항하기 위해 친환경 토양안정재를 적용하고, 적정 배합비 결정을 위해 장기침수시험과 유수저항시험을 실시하였다. 친환경토양안정재와 기존의 녹화토기반재를 활용한 장기침수시험결과, 토양안정재의 혼합율 0%는 30시간, 2%는 40일 후 100% 붕괴가 발생되었으며, 4% 이상의 혼합비에서는 실험종료시까지 시료의 원형이 그대로 남아 있어 2% 이상의 토양안정재가 극한 조건에서도 형상을 유지하는데 영향을 줄 수 있는 혼합비임을 확인하였다. 또한, 식생기반재의 구조적 안정성을 평가하기 위해 인공강우시험을 40, 45, $55^{\circ}$ 경사비탈면에 대해 실시하였으며, 토양안정재의 혼합비 0, 4, 8%에 대해 유수저항시험을 실시하고 침식저항능력을 평가하였다. 실험결과, 토양안정재의 혼합에 따라 유실률이 급격히 감소하는 경향을 보이는 등 비산을 방지하거나 우수에 의한 침식에 저항하기 위해 적용한 친환경 토양안정재가 큰 유실감소효과를 거둘 수 있을 것으로 판단된다.

• 수산해양기술연구
• /
• 제31권4호
• /
• pp.413-422
• /
• 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.

• 동력기계공학회지
• /
• 제2권2호
• /
• pp.35-40
• /
• 1998

In this study, the author investigated the effects of strengthening treatments on the mechanical properties of plasma sprayed Ni-base self fluxing alloy. Strengthening treatments for sprayed specimens were carried out in 4 different temperature conditions in vacuum furnace. The mechanical properties, such as microhardness, thermal shock resistance and erosion resistance were tested for the sprayed specimens after strengthening treatments. And it was proved that the mechanical properties of coating layer were much improved by strengthening treatments.

• 전기학회논문지
• /
• 제68권1호
• /
• pp.61-68
• /
• 2019

Only the power is converted from AC to DC, in accordance with IEC 60587 based test method, in order to develop the LSR(Liquid Silicone Rubber) insulator material for HVDC, the experiment of Inclined Plate Tracking and Erosion Resistance was conducted. A contaminant (2.5 mS/cm: ammonium chloride) was applied at a rate of 0.3 ml/min and a voltage of ${\pm}3.5kV$, and was evaluated on the basis of 60 mA/2s. The samples were prepared by dispersing LSR/Nano silica_25wt% Composites in LSR. The erosion phenomena of surface discharge and tracking due to DC polarity and negative polarity were measured by image, leakage current maximum and thermal camera. The thermal imaging camera measured the surface temperature generated by the joule heat of the leakage current due to the drying discharge and the conductive current. After the measurement, the tracking and erosion mechanisms were evaluated for erosion weight, erosion depth and erosion length. Positive and negative polarity of LSR/Nano Silica_25wt% composite Tracking and erosion results show that positive polarity is more severe than negative polarity.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 하계학술대회 논문집 C
• /
• pp.1500-1502
• /
• 1997

We investigated the tracking and erosion resistance of the silicone rubber by Inclined-Plane Method. And, with the variation of the accelerated conditions such as the applied voltage and composition of contaminant, the change of the tracking characteristics according to such conditions was evaluated. The leakage current significantly increases with the increasing voltage, but the weight loss remains almost the same. The voltage above 5.0 kV isn't recommended because tracking breakdown occurs as fast as it does without erosion, and the typical discharge waveform was the form of rectifying wave.

• 한국지반환경공학회 논문집
• /
• 제22권12호
• /
• pp.65-70
• /
• 2021

우리나라 제방 중 내부침식에 의한 붕괴는 약 10% 이상을 차지하고 있다. 내부침식 뿐만 아니라 월류, 제체 불안정 등으로 인한 제방의 붕괴를 사전에 방지하고 최소한의 피해를 위하여 다양한 연구들이 시도되고 있고, 그 중 하나가 바이오폴리머 적용에 관한 연구이다. 바이오폴리머의 적용 분야에는 강도, 식생, 내침식성으로 나뉘며 본 연구에서는 내침식성에 대한 내용을 다룰 것이다. 본 연구의 목적은 모형제방의 다짐도 및 내부침식 유도로에 따른 붕괴양상을 검토하고 적합한 조건을 선정하여 바이오폴리머 혼합토 제방의 효과를 검증하기 위한 실규모 실험 기초자료를 확보하는 것이다. 모형제방의 다짐도를 상, 중, 하로 나누어 각각의 유도로 조건에 따른 침식양상을 검토하여 가장 적합한 실험 조건을 선정하였으며, 바이오폴리머 혼합토 처리 유무에 따른 효과를 확인하였다. 실험결과, 바이오폴리머 혼합토를 적용한 제방에서의 내부침식률이 크게 감소하였으며, 실제 제방에 적용이 가능할 것으로 판단된다. 그러나 본 연구에서는 스케일을 축소시킨 모형제방에 바이오폴리머 혼합토를 적용하여 실제 적용 가능한지 여부를 연구하였다. 따라서, 실제 현장적용성 평가를 위해서는 실규모 제방실험이 필요할 것으로 판단된다.

• Advances in concrete construction
• /
• 제6권1호
• /
• pp.15-28
• /
• 2018

In the present investigation, influence of various material parameters on the cavitation erosion resistance of concrete was investigated on the basis of laboratory experiments. As there is no well-established laboratory test method for evaluating the cavitation resistance of concrete, a test set up called 'cavitation jet' was specially established in the present study in order to simulate the cavitation phenomenon experienced in the hydraulic structures. Various mixtures of concrete were designed by varying the grade of concrete, type and quantity of pozzolana, type of aggregates and cement type to develop good cavitation resistant concrete constructed using marginal aggregates. Three types of aggregates having three different Los Angeles abrasion values (less than 30%, between 30% and 50% and more than 50%) were employed in this study. To evaluate the cavitation resistance a total of 60 cylindrical specimens and 60 companion cubes were tested in the laboratory respectively. The results indicate that cavitation resistance of concrete degrades significantly as the L.A. abrasion value of aggregates goes beyond the 30% value. Incorporation of pozzolanic admixtures was seemed to be beneficial to enhance the cavitation resistance of concrete. Influence of other material parameters on the cavitation resistance of concrete was also noted and important observations have been made in the paper.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2000년도 하계학술대회 논문집 C
• /
• pp.1560-1562
• /
• 2000

The paper reports on a study of the influence of the silicone oils on the tracking and erosion resistance and hydrophobicity of SIR. Two silicone oils(A, B) having different chemical structure were selected in consideration of goof hydrophobicity and processability. Tracking and erosion resistance of SIR was investigated by the rotating wheel dip test (RWDT). In this test tracking and erosion areas due to glow and partial arc discharges cause an increase in the leakage current with an increase in time. Leakage current of SIR was decreased with increasing ratio of oil A/B. SIR was exposed to corona discharges in air and the specimens were analyzed with contact angle. It was observed that the contact angle of SIR was increased gradually in time. The recovery of hydrophobicity was increased with increasing ratio of oil A/B.