• Laser Solutions
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• v.2 no.1
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• pp.16-21
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• 1999

The surface of Alloy 600 was alloyed using a continuous wave $CO_2$ laser beam in order to improve its corrosion resistance. Laser surface alloying (LSA) was done by melting the surface electroplated with Cr of the alloy. The Cr concentration of the alloyed surface was 28-30 at.%, which is similar to that of Alloy 690. Alloying elements in the alloyed layer was observed to be distributed very homogeneously all over the alloyed region. According to the electrochemical and modified Huey tests, the corrosion resistance, in particular the grain boundary corrosion resistance, of the LSA specimens was significantly improved, compared with that of the as-received(AR) specimen. This improved corrosion resistance of the alloyed specimen might be attributed to the high Cr content which could make possible formation of more stable and dense passive film onto its surface.

• Laser Solutions
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• v.13 no.3
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• pp.19-26
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• 2010

In this study, fundamental experiment was conducted with various strength of UHSS (Ultra High Strength Steel) by $CO_2$ laser. And then, butt and lap joint laser welding with boron alloyed steel and Al-Si coated boron alloy steel have been done by changing laser beam feature, existence of gap and existence of coating layer to know welding characteristics of those materials. As a result, in case of fundamental experiment with various strength steel, hardening was found in the weld metal of all tested materials and softening was found at the heat affected zone of SGAFC 1180. In case of laser butt welding of UHSS, mechanical properties was improved by using small laser beam diameter and Al-Si coating layer caused fracture of weld metal. In case of laser lap welding of UHSS, Al-Si coating layer resulted in formation of intermetallic compound at the fusion boundary where fracture occurred. Al-Si coating layer caused lowering mechanical properties of weld metal.

• Korean Journal of Materials Research
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• v.2 no.6
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• pp.436-442
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• 1992

When $N_2$was used as shielding gas during the formation of Ti surface-alloyed layer by irradiation of $CO_2$laser beam on steel, TiN and F$e_2$Ti were formed regardness of carbon-content in steel. When Ti content was increased in low carbon-content steel, formation of martensitic structure was suppressed due to increase of critical cooling rate for martensitic transformation. In case of high-carbon steel, even though Ti content was about 1.5% in alloyed layer, hardness was increased by formation of martensitic structure instead of ferrite. In addition to that structure, hardness was incrreased further by precipitation of TiC in Ti alloyed-layer of high carbon-steel.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.364-366
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• 1995

We investigated the Electromigration characteristics in Cu alloyed Al line and the effect of Ti/TiN barrier layer on the characteristics. Test structures were fabricated by wafer level and 50% failure times were tested in the condition of j= 2 MA/$cm^3$, T= 300$^{\circ}C$. The reliability of Al line was improved which was 0.5%Cu Alloyed, but Ti/TiN under layer deteriorated the reliability while TiN over layer improved the characteristics.

• Journal of Welding and Joining
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• v.17 no.5
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• pp.107-115
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• 1999

The objective of this research was to study the formation of the thick hardened layer with the addition of metal powder(Cu) and ceramics powders(TiC) on the aluminum 5083 alloys by plasma transferred arc process(PTA process) and to characterize the effect of overlaying conditions on the overlaid layer formation. This was followed by investigating the microstructures of the overlaid layers and mechanical properties such as hardness and wear resistance. The overlaid layer containing copper powder was alloyed and intermetallic compound($CuAl_2$) was formed. The overlaid layers with high melting point TiC powders, however, did not react with base metal. Wear resistance of the alloyed layer was remarkably improved by the formation of $CuAl_2$, precipitate phase, which prevented wear of base aluminum alloys and at higher wear speed, accelerated sliding of the counter part. Wear resistance of the composite layer was also remarkably improved because TiC powder act as a load barring element and Fe debris fragments detached from the counter part act as a solid lubricant on the contact surface.

• Laser Solutions
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• v.2 no.1
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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.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.4
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• pp.555-562
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• 1990

Alloyed ohmic contact properties of Au-Zn/Au, Au-Be/Au,Au-Zn/Cr/Au, and Au-Be/Cr/Au metal system to p-InP were investigated. Optimum alloying conditions were obtained at the annealing temperature of 425\ulcorner for all the metal systems using a rapid thermal annealing system. Surface AES analysis and auger depth profiling were done for each metal system annealed at the optimum conditions. Outdiffusions of In and P from the InP substrate were found in the metal systems without Cr intermediate layer. Also, small amount of In. P and Cr were detected at the surface in the case of Au-Zn/Cr/Au system, while there were occured no outdiffusion of In, P, and Cr for Au-Be/Cr/Au system. The best surface morpholoty and specific contact resistivity of 4.5x 10**-5 \ulcornercm\ulcornerhave been obtained in this Au-Be/Cr/Au material system alloyed at 425\ulcorner for 60 second.

• Journal of the Korean Society for Heat Treatment
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• v.12 no.3
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• pp.221-230
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• 1999

The surface nitrogen permeation of Al alloyed 0.14%C-13%Cr stainless steels was investigated after heat treating at $1050^{\circ}C{\sim}1150^{\circ}C$ in the nitrogen gas atmosphere. The strong affinity between Al and nitrogen permeates the nitrogen through the interior of the steels. Two precipitates of round type and needle type are observed at the surface layer. These precipitates mainly consist of AlN containing plenty of aluminum. The surface layer of 0.53%Al alloyed specimen shows ferrite phase, while the surface layers of 1.65%Al and 2.27%Al alloyed specimens appear ${\gamma}$ plus ${\alpha}$ phases. The depth of nitrogen permeation depends upon the Al content and microstructure of the matrix. The 1.65%Al alloyed specimen representing ${\alpha}+{\gamma}$ matrix phases at the nitrogen permeation temperature shows the maximum case depth in this experiment. Although the surface hardness increases by raising the Al content of the specimen owing to the increase of nitride precipitation density, the nitride precipitation deteriorates the corrosion resistance in the solution of HCl, $H_2SO_4$, and $FeCl_3$.

• Korean Journal of Metals and Materials
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• v.48 no.6
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• pp.523-532
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• 2010

Co-application of organic coating and cathodic protection has not provided enough durability to low-alloyed steels inseawater ballast tank (SBT) environments. An attempt has made to study the effect of alloy elements (Al, Cr, Cu, Mo, Ni, Si, W) on general and localized corrosion resistance of steels as basic research to develop new low-allowed steels resistive to corrosion in SBT environments. For this study, we measured the corrosion rate by the weigh loss method after periodic immersion in synthetic seawater at $60^{\circ}C$, evaluated the localized corrosion resistance by an immersion test in concentrated chloride solution with the critical pH depending on the alloy element (Fe, Cr, Al, Ni), determined the permeability of chloride ion across the rust layer by measuring the membrane potential, and finally, we analyzed the rust layer by EPMA mapping and compared the result with the E-pH diagram calculated in the study. The immersion test of up to 55 days in the synthetic seawater showed that chromium, aluminium, and nickel are beneficial but the other elements are detrimental to corrosion resistance. Among the beneficial elements, chromium and aluminium effectively decreased the corrosion rate of the steels during the initial immersion, while nickel effectively decreased the corrosion rate in a longer than 30-day immersion. The low corrosion rate of Cr- or Al-alloyed steel in the initial period was due to the formation of $Cr_2FeO_4$ or $Al_2FeO_4$, respectively -the predicted oxide in the E-pH diagram- which is known as a more protective oxide than $Fe_3O_4$. The increased corrosion rate of Cr-alloyed steels with alonger than 30-day exposure was due to low localized corrosion resistance, which is explained bythe effect of the alloying element on a critical pH. In the meantime, the low corrosion rate of Ni-alloyed steel with a longer than 30-day exposure wasdue to an Ni enriched layer containing $Fe_2NiO_4$, the predicted oxide in the E-pH diagram. Finally, the measurement of the membrane potential depending on the alloying element showed that a lower permeability of chloride ion does not always result in higher corrosion resistance in seawater.

• Journal of the Korean institute of surface engineering
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• v.32 no.1
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• pp.10-20
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• 1999