• 열처리공학회지
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• 제23권4호
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• pp.198-204
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• 2010

Modified 9Cr-1Mo steels possess excellent high-temperature mechanical properties and are widely used in energy conversion industries. However, in-service materials degradation, such as softening, carbide-induced embrittlement, temper embrittlement, etc., can take place during long-term operation. Evolution of microstructure due to service exposure to high temperature has a strong effect on the performance of heat resistant steels. In case of modified 9Cr-1Mo steels, precipitation of $Fe_2Mo$-type laves phases and coarsening of $M_{23}C_6$-type carbides are the primary cause of degradation of mechanical properties such as toughness, hardness, tensile strength and creep resistance. This study was aimed at finding reliable parameter for assessing the integrity of modified 9Cr-1Mo steels. Characteristic parameters were attained between mechanical and ultrasonic properties.

• 대한금속재료학회지
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• 제46권4호
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• pp.209-216
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• 2008

Super austenitic stainless steels shows the high PRE (Pitting Resistance Equivalent) number and the good corrosion resistance. This work controlled the Co contents in Fe-31Cr-1.7Mo-27Ni-0.25N alloys to elucidate the effect of cobalt contents on the biocompatibility and corrosion resistance. Increasing Co contents, the hardness of the annealed alloys tends to be reduced. In aged alloys, cobalt decreased the increments of hardness by aging treatment. Cobalt decreased the critical pitting temperature (CPT) in 6% $FeCl_3$ + 1% HCl solution, but improved the anodic polarization behavior in Hanks' balanced salt solution and artificial saliva solution. Repassivation rate in artificial body solutions was improved by increasing cobalt contents, but didn't show the linear relationship to PRE number of the alloys. The experimental alloys showed the non-cytotoxicity because of its high corrosion resistance.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.563-564
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• 2006

The effect of different cooling rate on the structure and mechanical properties of Fe-3%Mn-(Cr)-(Mo)-0.3%C steels is described. Pre-alloyed Astaloy CrM and CrL, ferromanganese and graphite were used as the starting powders. Following pressing in a rigid die, compacts were sintered at $1120^{\circ}C$ and $1250^{\circ}C$ in $H_2/N_2$ atmospheres and cooled with cooling rates $1.4^{\circ}C/min$ and $6.5^{\circ}C/min$. Convective cooled specimens were subsequently tempered at $200^{\circ}C$ for 60 and 240 minutes.

• 한국표면공학회지
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• 제51권3호
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• pp.149-156
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• 2018

The corrosion and strength degradation characteristics of 1.25Cr-0.5Mo steels were studied under $650^{\circ}C$ in $76%N_2+6%O_2+16%CO_2+2%SO_2$ gas condition up to 500 hrs. Corroded specimens were characterized by weight gain, scanning electron microscope(SEM), energy dispersive X-ray spectroscopy(EDS), and X-ray diffraction(XRD). The tensile test was conducted to evaluate the mechanical strength and fracture mode with corrosion at high temperature. As the results of the experiments, thick Fe-rich oxide layers over $200{\mu}m$ were formed on the surface within 500 hrs. The thick oxide layers are formed with reduction of the cross-sectional area of the specimens. Thus, the strength tended to decrease with reduction of the cross-sectional area.

• 한국분말재료학회지
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• 제28권5호
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• pp.375-380
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• 2021

In this study, we investigate the effect of the duration of mechanical alloying on the microstructures and mechanical properties of ODS ferritic/martensitic steel. The Fe(bal.)-10Cr-1Mo pre-alloyed powder and Y₂O₃ powder are mechanically alloyed for the different mechanical alloying duration (0 to 40 h) and then constantly fabricated using a uniaxial hot pressing process. Upon increasing the mechanical alloying time, the average powder diameter and crystallite size increased dramatically. In the initial stages within 5 h of mechanical alloying, inhomogeneous grain morphology is observed along with coarsened carbide and oxide distributions; thus, precipitate phases are temporarily observed between the two powders because of insufficient collision energy to get fragmented. After 40 h of the MA process, however, fine martensitic grains and uniformly distributed oxide particles are observed. This led to a favorable tensile strength and elongation at room temperature and 650℃.

• 한국산학기술학회논문지
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• 제9권6호
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• pp.1555-1559
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• 2008

$5{\sim}150{\mu}m$의 오스테나이트계 304(Fe-18%Cr-12%Ni) 및 316L(Fe-18%Cr-13%Ni-2.4%Mo)미립 분말을 사용하여 소결 특성을 평가한 결과, 다음과 같은 결론을 얻었다 (1) 3.6ks의 소결 시간으로는 어느 경우에 있어서나 소결조건에 관계없이 소결체의 상대밀도는 $95{\sim}98%$에서 포화하여 완전 치밀화된 소결체를 얻을 수 없었다. (2) $5{\mu}m$분말을 진공소결 하였을 경우, ts=57.6ks에서 거의 완전 치밀화된 소결체가 얻어졌다. (3) 소결 분위기에 상관없이 304 및 316L소결체에는 $0.5{\sim}0.6%$정도의 산소가 잔류하였다. (4) 진공 소결의 경우, 탄소분 첨가에 의해 소결체의 잔류 산소량은 무첨가 소결체에 비하여 0.375이상 감소하였고, 조직적으로도 산화물은 거의 관찰되지 않았다. 또한 탄소 첨가는 소결체의 밀도 향상 효과로 작용하여 목적하는 완전 치밀화된 고성능 소결체를 제조하는 것이 가능하게 되었다.

• Environmental Engineering Research
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• 제21권3호
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• pp.247-255
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• 2016

Ten trace elements (Mg, Ca, V, Cr, Mn, Fe, Cu, Zn, Mo, and Cd) were determined in seven traditionally used wild medicinal plants of the Nagas in the North-East India viz Cynoglossum furcatum Wallich, Elsholtzia blanda Bentham, Lycopodium cernuum Linnaeus, Potentilla fulgens Wallich ex Hooker, Swertia macrosperma C.B. Clarke, Thalictrum foliolosum DC and Valeriana jatamansi Jones. Plant samples were dried, weighed, digested and analyzed for their mineral distribution level ranging from trace to major elements by graphite furnace-atomic absorption spectroscopy. All the medicinal herbs studied were found to contain the ten elements analyzed. The elemental concentration is given in mg/kg. Mg and Ca are present in high concentrations in both the roots and leaves of the plant samples. Among trace transition metals Fe had the highest concentration, followed by Mn, Cr, Cu, V, Zn, and Mo. Analysis showed that the toxic Cd element was at a lower concentration and is within the permissible limit of FAO/WHO, California standards and United States Pharmacopeia Limit for Nutritional Supplements.

• Corrosion Science and Technology
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• 제6권2호
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• pp.56-61
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• 2007

Carbide dissolution during heating processes can change chemical composition of martensitic stainless steel in its austenitic phase. Although the austenitizing treatments were carried out at a homogeneous austenite region, the amount of carbon atom in the matrix differs. Increase in the amount of carbon contents in the matrix resulted in decreasing MS temperature, which consequently causes the volume fraction of the retained austenite to increase. This study reveals the effects of the austenitizing treatment on the properties of Fe - 0.3C - 14Cr - 3Mo martensitic stainless steel change with different austenitizing temperatures.

• Journal of Welding and Joining
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• 제15권4호
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• pp.78-89
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• 1997

This study has evaluated the weld metal solidification cracking behavior of several Ni base superalloys (Incoloy 825, Inconel 718 and Inconel 600). Austenitic stainless steels(304, 310S) were also included for comparison. In addition, a possible mechanism of solidification cracking in the fusion zone was suggested based on the extensive microstructural examinations with SEM, EDAX, TEM, SADP and AEM. The solidification cracking resistance of Ni base superalloys was found to be far inferior to that of austenitic stainless steels. The solidification cracking of Incoloy 825 and Inconel 718 was believel to be closely related with the Laves-austenite (Ti rich in 825 and Nb rich in 718) and MC-austenite eutectic phases formed along the grain boundaries during solidification. Cracking in Inconel 600 was always found along the grain boundaries which were enriched with Ti and P. Further, solidifidcation cracking resistance was dependent not only upon the type of love melting phases but also on the amount of the phases along the solidification grain boundaries.

• 한국환경생태학회지
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• 제13권3호
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• pp.288-294
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• 1999

경상북도 안동 사문암지역 및 부근의 화강암지역에 분포하는 암석, 토양 및 식물체에 함유되어 있는 원소의 농도를 조사한 결과는 다음과 같다. 본 조사지역에분포하는 사문암에 함유되어 있는 주요 전이원소 함량(Ni 1.164ppm. Cr 366ppm. Co 109ppm. Fe 7.48%) 및 다른 대부분의 전이원소(Sc, Mn, Cu)도 화강암보다 높았으며 우리나라 efms 지역의 사문암에 함유되어 있는 농도와 비교하여 볼 때 매우 유사한 경향을 보이고 있다. 사문아토양의 경우 암석풍화토양 및 산림토양 모두 화강암토양에 비해 Ni, Co, Cr, Fe, Sc, Mn, Cu, Mg, Zn 농도가 높았으며 Pb는 반대의 경향을 나타내었다. 토양내 원소 함량은 이들의 모암에 함유되어 있는 원소 함량의 변화와 일치하고 있으며 같은 모암인 경우 산림식생의 영향에 따라 면 원소들의 차이가 다소 나타났다. 식물체 내 원소의 농도는 토양의 농도에 비해 모두 낮았다. 참억새, 쑥, 소나무에 함유되어 있는 원소별 평균 농도는 모두 동일종간 대부분의 전이원소(Ni, Co, Cr, Fe) 및 As 농도가 화강암토양에 비해 사문암토양에서 더높았다 사문암토양에서 생육하는 식물체 3종 모두 대부분의 원소(Ni, Co, Cr. As, Sc, Fe) 함랴이 지하부에서 더 높았으며 Zn과 Mo는 지상부와 지하부의 농도 차이가 크게 나타나지 않았다 화강암토양에서 생육하는 식물체의 경우 원소별 지상부 및 지하부의 농도차이는 사문암토양에 비해 크지 않았다.