• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.39-48
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• 2020

The present study investigates the chemical reaction and performance of ternary blended binders by mixing ferronickel slag. Cement was replaced using ground granulated blast furnace slag and ferronickel slag, combined up to 50% of the replacement rate. The blended cements were tested by setting times, length change, compressive strength at 1, 3, 7, 28 days. X-ray diffraction and scanning electron microscope were conducted for detecting hydration products while the MIP and microhydation heat were used for examining morphological characteristics. The results showed that by adding ferronickel slag, Pozzolanic reaction occurred, forming a dense pore structure and the effect of reducing hydration heat and dry shrinkage was also found. The compressive strength at 28 days was lower than that of 100% OPC control specimen (OSP0), but ternary blended cements showed no significant difference compared to binary blended (OSP50). If the optimal mix is derived later and used for the purpose, the potential for use as a cement binder is expected.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.5
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• pp.224-228
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• 2014

Recently, the demands for separation/recovery of valuable metals such as nickel or tin from copper based alloys has been attracting much attention from the viewpoints of environmental protection and resource utilization. In this report, experimental results on concentration increasement of nickel and tin compared to the previous report are investigated. Ni is successfully separated by a organic solvent and reduced to the metal powder whose concentration is over 98 %. Sn is separated by a selective solution method and its concentration is increased to 97.5 % by three consecutive solution and reduction process. Crystal structure, surface morphology and microstructure of the separated samples are studied.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.12 no.1
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• pp.41-48
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• 2016

To investigate the effect of long-term thermal aging on the microstructural and mechanical characteristics of weldment made of nickel base alloy and its weld metal, an accelerated heat treatment was applied to simulate the process of long-term thermal aging in the operating condition of nuclear power plant. A representative nickel-based weldment with Alloy 600 and Alloy 182 was fabricated and heat-treated at $400^{\circ}C$ for 1,713 h and 3,427 h to simulate the thermal aging for the period equivalent to 15 and 30 years in operating pressurized water reactors, respectively. The microstructural and mechanical characteristics were analyzed by using optical microscopy, scanning electron microscopy and Vickers microhardness measurement. Changes were observed in precipitation behavior and microhardness of each specimen, and these changes were mainly attributed to the change in precipitated morphology and residual stress across the weld during the thermal aging process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2496-2501
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• 2000

High speed ball end milling is attracting interest in the aerospace industry for the machining of complex 31) airfoil surfaces in nickel based superalloys, Experimental work is detailed on the effect of cutter orientation on tool life, cutting forces, chip formation, specific force and workpiece surface roughness, when high speed ball end milling nickel based supperalloy(lnconel 718). Dry cutting was performed using 8min diameter solid carbide cutters coated with either TiA1N or CrN for the workpiece mounted at an angle of 45˚ from the cutter axis. A horizontal downwards cutting orientation provided the best tool life with cut lengths~50% longer than for all other directions. Evaluation of cutting forces and associated spectrum analysis of results indicated that cutters employed in a horizontal downwards direction produced the least vibration.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.6
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• pp.87-93
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• 2004

An experimental is carried out to investigate the characteristics of blanking for nickel alloy Alloy42 (t=0.203mm), a kind of IC lead frame material. By varying clearance between die and punch the shapes of shear profile are examined. Finite element analysis with element deletion algorithm for ductile fracture mode is also carried out to study the effect of clearance theoretically and to compare with experimental results. The rectangular shape specimen with four different comer radius is used to study the characteristics of blanking for straight side and comer region simultaneously. As the result the ratios measured k(m experiment of roll over, burnish and fracture zone based on initial blank thickness are compared with those of FE analysis. Both experiment and FE analysis show that the amount of mil over and fracture is increased as the clearance increases. When the radius of comer is less than thickness of blank it has been found that larger clearance is required than that of straight region in order to maintain same quality of shear profile at the comer region.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.205-210
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• 2008

Magnetic hysteresis loops of a nickel strip and a Fe-Co alloy strip, which have been used in magnetostrictive strip type guided wave transducers for long range ultrasonic testing of pipelines, were measured and then magnetic property effects of a strip on transducer sensitivity were analyzed. The sensitivity of an optimized Fe-Co strip transducer was superior to that of the nickel strip transducer by a factor of about 30. It was shown that this was mainly attributed to the differences in remanence magnetization and coercivity of the two magnetostrictive materials.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.71-76
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• 2008

The mechanical properties of Ni-Fe alloy were varied with the current type, current density and bath conditions such as concentrations and temperature. The effect of electroplating parameters on the surface hardness, mechanical strength, residual stress and wear properties were investigated. The mechanical properties of electrodeposits with PC plating is superior to those with DC plating. Ni-Fe electrodeposits with PC has approximately 50% lower residual stress than that of DC plating. The tensile strength of PC electroplated specimen was 15% higher than that of DC electroplated specimen. The wear resistance of PC specimen was 30% improved relative to that of DC specimen.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.121-126
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• 2007

This study aims at investigating the effect of heat treatment conditions on the dry sliding wear behavior of thermally sprayed Ni-based self-flux alloy coatings. Ni-based self-flux alloy powders were sprayed onto a carbon steel substrate and then heat-treated at 700, 800, 900 and $1000^{\circ}C$ for 30 minutes in a vacuum furnace. Dry sliding wear tests were performed using sliding speed of 0.4 m/s and applied load of 6 N. AISI 52100 ball(diameter 8 mm) was used as counterparts. Microstructure and wear behavior of both as-sprayed and heat-treated Ni-based self-flux alloy coatings were studied using a scanning electron microscope(SEM), energy dispersive X-ray spectroscopy(EDX), electron probe micro-analysis(EPMA) and X-ray diffraction(XRD). It was revealed that microstructure and wear behavior of thermally sprayed Ni-based self-flux alloy coatings were much influenced by heat treatment conditions.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.135-135
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• 2017

제염기술은 원자력발전소의 순환계통장치 및 기기류의 방사성 오염물질을 제거하는 기술이다. 현재 국내 원전의 설계 수명 및 유지보수 시기가 도래함에 따라, 작업 전 작업자의 방사선 피사량을 극소화하기 위한 제염 기술이 주목을 받고 있다. 제염 방법에는 크게 기계적 제염과 화학약품을 사용하는 화학제염이 있다. 그 중 화학제염은 복잡한 구조의 제염 대상물에 대한 큰 효과 및 간단한 공정 때문에 주로 사용되고 있다. 제염 시 방사성 산화물과 오염성분을 제거하기 위해 강산 또는 강알칼리의 화학용액이 사용된다. 강한 화학약품을 사용함으로써 큰 제염효과를 얻을 수 있는 반면, 금속 재료의 부식에 대한 구동력도 커지게 된다. 금속 재료의 경우, 강한 부식성 환경에서 공식(pitting corrosion) 및 입계부식(intergranular corrosion)형태의 손상이 크게 발생하기 때문에, 제염공정 시 사용되는 화학용액에 대한 재료의 건전성 검증이 반드시 필요하다. 본 연구에서는 원전기기용 재료인 니켈합금강 Inconel600의 화학제염 시 시험공정 3가지에 대한 부식손상 특성을 규명하였다. 산화공정은 $HMnO_4$ 실험용액을 공통으로 사용하였으며, 산화공정 종료 후 환원공정은 각 시험공정에 따라 환원공정 1은 2000ppm $H_2C_2O_4$, 환원공정 2는 1500ppm $H_2C_2O_4$ + 500ppm $H_8C_6O_7$, 그리고 환원공정 3은 3000ppm $H_2C_2O_4$ 실험용액을 각각 투입하여 수행하였다. 산화, 환원공정을 1Cycle로 하여 온도 $75^{\circ}C$로 유지된 용액에 각 2시간씩 침적하였다. 각 시험공정 별로 총 5Cycle을 실시하였다. 각 시험공정 Cycle종료 후 시험편을 취외하여 무게감량측정, SEM(Scanning electron microscope)분석, 3D현미경분석 그리고 타펠분극 실험을 실시하였다. 각 분석결과를 토대로 하여, 니켈합금 Inconel600에 대한 화학제염 시 시험공정에 따른 부식특성을 규명하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.11-17
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• 2016

Powder metallurgy nickel based superalloy has been used in a high temperature part of turbine engine for airplane. The fatigue crack growth behavior was investigated using CT specimens for the materials at room temperature(R.T.), $600^{\circ}C$ and $700^{\circ}C$. The direct current potential drop(DCPD) method suggested by ASTM E647 was used to measure the crack length during fatigue crack growth at various stress ratios. The fatigue crack growth rate at R=0.5 was faster than that at R=0.1 for all temperature conditions and increased with the increase of stress ratio and temperature. Fractography was conducted for analysis of fracture mechanism.