• International Journal of Advanced Culture Technology
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• 제8권2호
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• pp.246-251
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• 2020

Dimethyl Ether(DME) engine use a highly efficient alternative fuel having a great quantity of oxygen and has a advantage no polluting PM gas. The existing DME fuel cam material is a highly expensive carbide alloy, and it is difficult to take a price advantage. Therefore the study of replacing body area with inexpensive steel material excluding piston shoe and contact area which demands high characteristics is needed. The development of WC-Ni base carbide alloy optimal bonding composition technique was accomplished in this study. To check out the influence of bonding temperature and time, bonding characteristics of sintering temperature was experimented. The hardness of specimen and bonding rate were measured using ultrasound equipment. The bonding state of each condition was excellent, and the thickness of mid-layer, temperature and maintaining time were measured. The mid-layer thickness according to bonding temperature and maintaining time were observed with optical microscope. We analyzed the micro-structural analysis, formation of bonding specimen, wafer fabrication and fuel cam abrasion test. Throughout this study, we confirmed that the fuel cam for DME engine which demands high durability against velocity and pressure is excellent.

• International Journal of Precision Engineering and Manufacturing
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• 제5권1호
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• pp.19-26
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• 2004

The growth of solid particles in TiC-XC-2vo1.% and TiC-XC-30vo1.% Ni alloys, (where X=Zr, W or Mo) was fitted to the equation of the form $d^3$-${do}^3$=Kt during the liquid phase sintering at 1,673K. Also, the grain growth behavior decreased markedly with the addition of ${MO}_2$C or WC and increased with the addition of zrC. The contiguity was greater in the alloys with a smaller growth rate constant and especially, decreased by increasing the Ni content in the TiC-${MO}_2$C-Ni alloy. In addition, the effect of the addition of carbide on the grain growth of 2 vo1.% Ni alloys was found to be similar to that of 30vo1.% Ni alloys. Consequently, the grain growth mechanism cannot be explained by the usual solution / reprecipitation process, but can be explained in terms of a new growth velocity equation, which includes the effects of contiguous carbide grain boundaries in restricting the overall grain growth, as well as the area of the solid / liquid interface in the alloy.

• Journal of Welding and Joining
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• 제32권6호
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• pp.41-46
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• 2014

In this study, cracking susceptibility of laser cladding was investigated according to the processing parameters such as laser power, scan speed and feeding rate with blended powders of stellite#6 and technolase40s (WC+NiCr). The solidification microstructure of clad was composed of Co-based dendrite structures with ${\gamma}+Cr7C3$ eutectic phases at the dendritic boundaries. The crack propagation showed transgranular fracture along dendritic boundaries due to brittle chrome carbide at the eutectic phases. From results of fractography experiments, the fracture surface was typical cleavage brittle fracture in the clad and substrate. The number of clad cracks, caused by a tensile stress after the solidification, increased with increase of laser power, scan speed and feeding rate. Increase of the laser power caused large pores by facilitating WC decarburizing reaction. And the pores affected increase of crack susceptibility. High scan speed caused increment of clad cracks due to thermal stress and WC particle fractures. Also, increase of the feeding rate accompanied an amount of WC particles causing crack initiation and decarburizing reaction.

• Journal of Advanced Marine Engineering and Technology
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• 제36권2호
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• pp.276-285
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• 2012

본 연구목적은 열간압연용 런-아웃 테이블 롤러 표면의 기계적 성질을 개선하기 위해 다공질 자용성 합금으로 피복하는 방법을 개발하는 것이다. 열간압연에서 런-아웃 테이블의 롤러 내구성을 높이기 위해서는 고온에서 롤러표면의 경도를 높게 유지해야 하고, 내마모성, 내식성, 내열성, 내소부성 및 내응착성의 향상을 유지하여야 한다. 또한, 고온의 열연 강판을 안정적으로 이송할 수 있도록 하기 위해서는 롤러표면에 적절한 마찰계수를 유지하도록 하여야 하고, 롤러와 강판 사이에 미끄럼 발생이 없어야 한다. 본 연구에서는 자용성 합금에 텅스텐카바이드를 첨가시켜 서메트화하여 롤러의 내마모성을 증대시켰고, 미세 철분말을 롤러표면에 피복하여 다공질을 만들어 마찰계수를 높이고 붙잡음성을 향상시켰다. 그 결과, Ni-Cr 피복 롤러에 비하여 다공질 자용성 합금 피복 롤러는 피복층에 철분이 5 ~ 10 wt%로 많이 함유되어 재용융 공정에서 전기로로 가열하여 일부분만 합금화되고 나머지는 산화 및 용해에 의해 탈락되어 다공질로 나타나 강판과의 붙잡음성을 향상시켰다.