• Applied Microscopy
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• 제45권1호
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• pp.32-36
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• 2015

The microstructural features of FeCoCrNi, FeCoCrNiAl and FeCoCrNiSix (x=0, 5, 10, 15, 20) alloys have been investigated in the present study. The microstructure of FeCoCrNi alloy changes dramatically with equiatomic addition of Al. The fcc irregular shaped grain structure in the as-cast FeCoCrNi alloy changes into the bcc interconnected structure with phase separation of Al-Ni rich and Cr-Fe rich phases in the as-cast FeCoCrNiAl alloy. The microstructure of FeCoCrNi alloy changes with the addition of Si. With increasing the amount of Si, the fcc structure of the grains is maintained, but new phase containing higher amount of Si forms at the grain boundary. As the amount of Si increases, the fraction the Si-rich grain boundary phase increases.

• 대한화학회지
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• 제56권4호
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• pp.448-458
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• 2012

In order to develop alloy resistance in aggressive sulphat ion, the corrosion behavior of metallic glasses $Ni_{92{\cdot}3}Si_{4.5}B_{32}$, $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ (at %) at different concentrations of $H_2SO_4$ solutions was examined by electrochemical methods and Scanning Electron Microscope (SEM) and X-ray Photoelectron Microscopy (XPS) analyses. The corrosion kinetics and passivation behavior was studied. A direct proportion was observed between the corrosion rate and acid concentration in the case of $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ alloys. Critical concentration was observed in the case of $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ alloy. The influence of the alloying element is reflected in the increasing resistance of the protective film. XPS analysis confirms that the protection film on the $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ alloy was NiS which is less protective than that formed on Cr containing alloys. The corrosion rate of $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$. alloys containing 7% and 13% Cr are $7.90-26.1{\times}10^{-3}$ mm/y which is lower about 43-54 times of the alloy $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ (free of Cr). The high resistance of $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ alloy at the very aggressive media may due to thicker passive film of $Cr_2O_3$ which hydrated to hydrated chromium oxyhydroxide.

• 한국전기전자재료학회논문지
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• 제20권6호
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• pp.520-526
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• 2007

In order to acquire fundamental informations to fabricate high precision thin film resistors, NiCr/NiCrSi alloy films were prepared using Ni and Cr targets. Effect of composition on the electrical properties of the NiCr/NiCrSi alloy film were then investigated. Considering the effect of Si doping on the electrical and material characteristics, the lower TCR (temperature coefficient of resistance) values could be achieved for samples with Ni/Cr ratio of $0.8{\sim}1.5$ (in a range of relative higher specific resistivity and Cr composition of $40\;wt%{\sim}55\;wt%$) and with Si doping. Consequently, the sample prepared using a DC power showed a good TCR of $-25\;ppm/^{\circ}C$, which implies that increase of specific resistivity and decrease of TCR would be achieved more efficiently not for Ni-Cr binary material but for Si doped Ni-Cr ternary material, and not using RF power but using DC power in the sputtering process.

• 대한치과기공학회지
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• 제40권3호
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• pp.125-131
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• 2018

Purpose: Automatic dental prosthesis manufacturing process was accelerated by the spread of dental CAD / CAM system. The CAD / CAM system with milling alloys were needed supplement. So, sintered alloy blocks were introduced. In this study, we want to study sintered alloy block. And to evaluate the alloy block manufacture and alloy properties. Methods: The alloy powders were prepared by high pressure water dispersion method. The sintered alloy blocks were prepared by low temperature pressing method. Their components observation were EDX, and the alloy structure was observed by XRD. Results: Co-Cr alloy powders were observed to have a circle shape with an average diameter of about $100{\mu}m$ and a Ni-Cr alloy powder had a circle shape with an average diameter of about $50{\mu}m$. The Co-Cr alloy block is composed of Co (34.62 wt%), Cr (17.33 wt%), Mo (2.98 wt%), Si (0.36 wt%) and C (44.17 wt%). The Ni-Cr alloy powder was composed of Ni (40.29 wt%), Cr (19.37 wt%), Mo (3.53 wt%), Si (0.52 wt%) and C (33.18 wt%). The peak of the Co and CoCr peaks were observed in the CoCr alloy body by the means of XRD study. Cr2Ni3 of the peak was observed in the Ni-Cr alloy material. Conclusion : As a result, the following conclusions were obtained. 1. Prepared by high-pressure water-law Co-Cr alloy powder has an average diameter $100{\mu}m$, Ni-Cr alloy powder was found to have the form of sphere having an average diameter $50{\mu}m$. 2. Co-Cr alloy and Ni-Cr alloy block produced by low-temperature processing showed a certain ratio. 3. In the XRD study, Co phase appeared in Co-Cr alloy block after sintering. and Cr2Ni3 phase appeared in Ni-Cr alloy block after sintering.

• 전기화학회지
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• 제18권2호
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• pp.68-74
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• 2015

본 실험에서는 리튬이차전지의 고용량 음극활물질로 주목받는 Si 합금의 부피팽창을 억제하기 위한 방법의 하나인 비활성-matrix상을 이용하고, 상태도를 이용하여 동일한 용량을 발현하는 Si계 이원계 합금 (Cr-Si, Ni-Si) 조성에서의 미세구조 및 전기화학적 특성을 비교/분석하였다. 급속응고공정(Rapid Solidification Process, Melt-spinning법)를 이용하여 동일조건하에서 리본 모양의 합금을 제작하였고, 제작된 리본합금은 동일조건에서 분쇄하여 X-선회절 (X-Ray Diffraction) 분석을 실시하였다. XRD 분석 결과, 상태도에서 예측된 것과 같이, 두 합금 모두 Si 상 및 비활성-matrix상($CrSi_2$ 및 $NiSi_2$)이 관찰되었으며, 이외의 제3의 상은 관찰되지 않았다. 또한, 주사전자현미경(SEM, Scanning Electron Microscope) 및 투과전자현미경-에너지분산분광법(TEM-EDS, Transmission Electron Microscopy - Energy Dispersive X-ray Spectroscopy)으로 미세구조를 살펴본 결과 Cr-Si 합금의 미세구조가 Ni-Si 합금보다 fine한 것을 알 수 있었고 이것은 상태도로부터 예측 가능하였다. 두 합금 조성에서 미세구조에 따른 전기화학적 특성을 비교 평가하기 위해 코인형 하프셀과 풀셀로 충방전 실험을 진행하였고 이와 별도로, 전극의 두께변화 측정이 가능하게 설계된 시험셀을 이용하여 반응 중 Si의 수축팽창을 측정하였다. coarse한 미세구조를 가진 Ni-Si 합금보다 fine한 미세구조를 갖는 Cr-Si 합금의 전극팽창이 비교적 잘 억제됨을 확인하였고, 충방전에 따른 수명 내구성도 우수함을 확인하였다. 이런 결과들로부터 합금의 조성에 따른 미세구조, 체적변화 및 전기화학적 열화와의 연관성을 유추할 수 있었다.

• 한국표면공학회지
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• 제31권5호
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• pp.297-303
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• 1998

The influences of vanadium addition on the cavitation erosion resistance pf Fe-Cr-Ni-Si-C hardfacing alloy were investigated using a vibratory apparatus up to 30 hrs. It was shown that 1wt.%V additioned alloy improved the resistance to cavitation damage. However, further increase in V content up to 2wt.% reduced the cavitation erosion resistance. It was considered that the addition of V developed the cavitation erosion resistance by reducing the stacking fault energy of Fe-Cr-Ni-Si-C alloy. However, the further increase in V content seemed to reduce the cavitation erosion resistance by increasing the matrix/carbide interfacial area, which was the preferential sites of the cavitation damage.

• 한국주조공학회지
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• 제27권3호
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• pp.120-125
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• 2007

The microstructure, mechanical properties and melting range of Ni-Cr-Mo based alloys were investigated to develop Be-free Ni-Cr-Mo base dental alloys for Porcelain-Fused-to-Metal Firing(PFM). All as-cast alloys showed dendritic structure. Rockwell hardness of 20Cr7Mo was increased with addition of Si and Ti. On the contrary, it was decreased with addition of Co. The duplex alloying elemental addition such as 3Co + xTi, 2Si + xCo and 2Si + xTi to 20Cr7Mo resulted in much increase of hardness. Rockwell hardness and compressive strength for 20Cr3CoSiTi or 17Cr6CoSiTi alloy that add Si-Ti had similar values compared to the commercial alloys. Melting range for 20Cr3CoSiTi and 17Cr6CoSiTi alloy that add Si-Ti showed similar or lower than commercial alloys. In conclusion, 20Cr3CoSiTi and 17Cr6CoSiTi alloys can be applied for commercial use.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2004년도 동계학술연구발표회 논문개요집
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• pp.91-92
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• 2004

• 한국표면공학회지
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• 제35권1호
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• pp.5-10
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• 2002

This study was performed to investigate the influence of spraying condition to the coating layer properties of Fe-Cr-Ni-Mo-Si-B alloy using the HVOF. The investigations, such as thickness measurement, surface roughness, hardness, friction coefficient, resistance of corrosion were carried out. Matrix is prepared by gritting and coating layer is made of Fe-Cr-Ni-Mo-Si-B alloy powder using HVOF. Alumina gritting layers are superior to steel gritting layers. The less spaying distance, the more coating layer properties confirmed. The optimum spraying condition, in this study, was proved as 13inch spraying distance with feed rate 350rpm (78g/min).

• 한국재료학회지
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• 제26권1호
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• pp.8-12
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• 2016

Effects of conventional rolling(CR) and differential speed rolling(DSR) on the microstructure and mechanical properties of Cu-Ni-Si alloy were investigated in detail. The copper alloy with thickness of 3 mm was rolled to 50 % reduction at ambient temperature without lubricant with a differential speed ratio of 2:1. The conventional rolling in which the rolling speed of upper and lower rolls is identical was performed under identical rolling conditions. The shear strain introduced by the CR showed positive values at positions of upper roll side and negative values at positions of lower roll side. However, it showed zero or positive values at all positions for the samples rolled by the DSR. The microstrucure and texture development of the as-rolled copper alloy did not show any significant difference between CR and DSR. The tensile strength of the DSR processed specimen was larger than that of the CR processed specimen. The effects of rolling methods on the microstructure and mechanical properties of the as-rolled copper alloy are discussed in terms of the shear strain.