• Journal of Welding and Joining
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• 제23권5호
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• pp.25-29
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• 2005

Steel has been mainly used in the automotive industry, because of good mechanical properties, weldability and so on. However, there has been increase in using aluminum to reduce the weight of vehicle. This leads to improve fuel efficiency and to reduce air pollution. A steel-aluminum hybrid body structure is recently used not only to reduce the weight of vehicle but also to increase safety. In this paper, the laser beam joining method is suggested to join steel and aluminum. To avoid making brittle intermetallic compounds(IMC) that reduce mechanical properties of the joint area, only aluminum is melted by laser irradiation and wetted on the steel surface. The brittle IMC layer is formed with small thickness at the interface between steel and aluminum. By controlling the process parameters, brittle IMC layer thickness is suppressed under 10 micrometers which is a criterion to maintain good mechanical properties.

• 한국표면공학회지
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• 제35권6호
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• pp.408-414
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• 2002

TiN and TiAlN coating layer were deposited on WC-Co steel substrates by an arc ion plating(AIP) technique. The crystallinity and morphology for the deposited coating layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The impact behaviors of the deposited TiN and TiAlN coating layer were investigated with a ball-on-plate impact tester. Beyond $10^2$ impact cycle, TiAlN coating layer showed superior impact wear resistance compared to TiN coating layer. On the other hand, both TiN and TiAlN coating layers started to be partially failed between $10^2$ and $10^3$ impact cycle. Above $10^3$ impact cycle, TiN and TiAlN coating layers showed similar impact behavior because of the substrate effect.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.215-215
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• 2014

Composites layer of Al-Cr-Ni-O system was prepared on a steel plate by hydro-thermal process at $700^{\circ}C$ for 12 hours, which phase identification and thermal conductivity were determined. The composites layer consisted of aluminum nitride, alumina, chromium carbide and aluminium, which density was $3.7kg/m^3$. The thermal conductivity of the coating layer determined by thermal data acquisition system was about 98.0 W/m/ which depended on the AlN content. Numerical modelling of the heat transfer behavior of the coating layer was well agreement with the empirical data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.280-285
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• 2000

It is very important to evaluate the surface or subsurface microstructure because of their influences on mechanical properties of materials. Surface SH-wave which is horizontally polarized shear wave traveling along near surface and subsurface layer is an attractive technique for material evaluation. The destructive method is widely used for the estimation of material degradation but it has a great difficulty in preparing specimens from in-service industrial facilities. In this study, nondestructive evaluation for degraded structural materials used at high temperature though surface SH-wave method is discussed. 2.25Cr-1Mo steel specimens which were prepared by the isothermal aging heat treatment at $650^{\circ}$ were evaluated though ultrasonic nondestructive evaluation techniques investigating the change of sound velocity, attenuation coefficient and amplitude spectra. In addition, it has verified experimentally the frequency-dependence of attenuation coefficient though wavelet analysis method.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2001년도 추계 학술발표강연 및 논문개요집
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• pp.104-104
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• 2001

• 한국산학기술학회논문지
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• 제6권5호
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• pp.391-395
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• 2005

본 논문은 합금공구강을 기계 가공한 시편과 와이어 컷 방전가공한 시편의 가공면 표면 특성을 비교 분석한 것이다. 와이어 컷 방전가공으로 금형을 제작하면 기계가공으로 가공하기 어려운 형상의 제품을 쉽게 제작할 수 있다. 그러나 기계가공으로 제작된 금형에 비해 수명이 현저히 저하된다. 이러한 요인은 와이어 컷 방전가공으로 제작 된 금형 표면에 가공 변질층이 발생하기 때문이라 사료된다. 두 시편의 표면 거칠기 측정 결과 1차 와이어 컷 방전가공한 시편의 표면 거칠기 분포가 거칠음을 알 수 있었다. 주사 전자 현미경 관찰 결과 두 시편의 표면부와 단면부는 큰 차이를 보였고 와이어 컷 방전가공한 시편의 단면부는 표면의 급열 급랭된 조직이 가공 변질층으로 존재함을 알 수 있었다.

• Journal of Electrochemical Science and Technology
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• 제4권2호
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• pp.61-70
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• 2013

Corrosion inhibition of carbon steel in 2M HCl by some benzohydrazide derivatives (I-III) was studied using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques at $30^{\circ}C$. Polarization studies showed that all the investigated compounds are of mixed type inhibitors. Temperature studies revealed a decrease in efficiency with rise in temperature and corrosion activation energies increased in the presence of the hydrazide derivatives, probably implying that physical adsorption of cationic species may be responsible for the observed inhibition behavior. Electrochemical impedance studies showed that the presence of benzohydrazide derivatives decreases the double layer capacitance and increases the charge transfer resistance. The adsorption of these compounds on carbon steel surface was found to obey Temkin's adsorption isotherm. Synergistic effects increased the inhibition efficiency in the presence of halide additives namely KI and KBr. An inhibition mechanism was proposed in terms of strongly adsorption of inhibitor molecules on carbon steel surface.

• 한국레이저가공학회지
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• 제2권1호
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• pp.22-29
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• 1999

This work was carried out as a fundamental experiment to fabricate a Graded-Boundary Ni/Steel material using a laser beam. A Ni sheet was placed on a steel substrate, and then a series of high power $CO_2$ laser beams were irradiated on the surface in order to produce a homogeneous alloyed layer. The processing parameters were : 4 ㎾ laser power, 2m/min traverse speeds, -2mm defocuing, 17 l/min sheiding gas flow rates. The sequential repetition of the laser surface alloying treatment up to 4 times, resulted in about 5mm thick of fair compositional gradient systems. In order to determine the microstructure, phase and compositional profiles in this material, optical microscopy, XRD and EDS were used. The compositions varied from 66% to 0% for Ni and 34% to 100% for Fe in this material The microstructures were typical morphologies of rapid solidification and solid-state cooling. Since compressive stress was formed in the heat affected region due to martensitic transformation, while relative tensile stress was developed in the alloyed region, cracks were formed between the alloyed region and the substrate region.

• 한국표면공학회지
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• 제32권4호
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• pp.547-554
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• 1999

The interfacial reaction, spangle and coating thickness of galvanized steel in Ni added Zn-0.18Al bath have been investigated. The size of spangle and thickness of reaction layer were observed under an optical microscope, SEM and EDS. Analysing the experimental results concerning spangle size of galvanized steel it was found that Ni addition in Zn-0.18Al bath tended to be minimized spangle size. For Zn-0.18Al bath, addition of 0.1Ni suppressed the formation of Fe-Zn intermetallic compounds but increased with Ni content above 0.1%. The coating thickness of galvanized steel was reduced with Ni addition in Zn-0.18Al bath, especially in Zn-0.18Al-0.05Ni bath. Addition of Al in Ni containing bath resulted in forming the Al-Ni intermetallic compounds such as $Al_3$Ni$_2$ and $Al_2$Ni which consist most of top precipitates.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2003년도 춘계학술발표회 초록집
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• pp.31-32
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• 2003

In the Present study, the effect of galvannealing conditions on the phase distribution of the Zn-Fe intermetallic phases in the coating layer of the galvannealed steel sheets(GA) was investigated in an interstitial free steel and two kinds of high strength steels. The composition profiles of the coating layers were analyzed using AA and EDS analysis, and the distribution of the intermetallic phases was examined with the aids of X-ray diffraction. On the basis of the pole figure and OIM analyses, it was clarified that the preferred orientation of the $\zeta$ phase depended on the development of the $\gamma$-fibre texture in the substrate.