• Journal of the Korean Society for Heat Treatment
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• v.9 no.3
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• pp.177-186
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• 1996

Surface alloying of Ti alloy by $CO_2$ laser is able to produce few hundred micrometers thick TiN or TiC surface-alloyed layer with high hardness on the substrate by injecting reaction gas($N_2$ or $CH_4$). Laser surface alloying by means of process control is in many applications essential in order to obtain predictable hardening layer. This research has been investigated the effect of such parameters on TiN and TiC gas alloying of Ti-6Al-4V alloy by $CO_2$ laser. The maximum surface hardness of TiN layer was obtained 1750Hv on the conditions of 0.8kW laser power, 0.8m/min scanning speed and 100% $N_2$ atmosphere. However, the maximum hardness of TiC formation layer after laser treatment was about 630Hv. As scanning speed was increased, the hardness and depth of these layers were decreased at constant laser power.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2006.06a
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• pp.52-55
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• 2006

• Korean Journal of Optics and Photonics
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• v.1 no.1
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• pp.98-106
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• 1990

Lasers are used increasingly for specialized engineering applications such as drilling, profile cutting, welding and surface heat-treatment(hardening, alloying, annealing0 of metals and non-metals. The most important characteristics of lasers used for these materials-processing applications are reviewed, with special emphasis on the importance of the controlled heating process. In addition to these processes, some optical devices and supplementary equipment used in laser processing are introduced. Finally, some examples shows the wide variety of laser capability for substitution of traditional materials processing.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.1
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• pp.53-62
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• 1987

High power lasers provide a controllable and precise energy source in surface transformation hardening. A careful control of the process is needed in order that the surface layer of the material reaches the austenizing temperature, but that it does not melt. In order to achieve this the results of theoretical and experimental studies on the laser surface hardening of a medium carbon steel are described. A two-dimensional computer program, which can be used generally for the determination of transient temperature distributions in welding and heat treatment, was established on the basis of the finite element method. For the confirmation of the accuracy of the numerical analysis, a medium carbon steel (SM 45C) of 5mm thickness was heat-treated with a 1kW CW CO$_{2}$ laser machine, while the traverse speed and the distance from the focal point (defocused distance) were varied. Experimental and numerical results showed a similar tendency in correlations between the hardened zone shape and the process parameters. With increasing beam spot diameter the width and depth of the hardened zone increased for relatively small beam spot diameters, but decreased rapidly after reaching the maximum value, while with increasing traverse speed the width and depth of the hardened zone decreased monotonously. Too small beam spot diameters are to be avoided, since the surface melting would lower the surface hardness and produce an uneven surface which may be unacceptable because of the possible requirement for subsequent machining. It could be observed that for a given traverse speed and laser power input there exists a optimal range of the beam spot diameter, which produce a large width of the hardened zone but no melting on the surface.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.13-17
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• 1993

Analytical models for the prediction of the size of hardened zone in laser surface hardening are presented. The models are based on the solutions to the problem of three-dimensional heat flow in plates with infinite thickness. The validity of the model was tested on medium carbon steel for Gaaussian mode of beam. Then the model for rectangular beam was used for the prediction of the size of harened zone on various hardening process parameters. From the calculation results it appeared that the size and shape of the hardened zone are strongly dependent on process parameters suchas beam mode, beam size, and traverse speed.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1475-1480
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• 2007

In the last few years, lasers have found new applications in production engineering as tools for surface treatment, cutting, welding, drilling and marking. So far, the laser has mainly been used in special laser processing machines ('laser-only') directly integrated into a production line or serving as stand-alone stations in the workshop. By combining conventional metal cutting technologies with laser processes in one machine, complete processing of a workpiece with different technologies in one setting can be realized. The main advantages are a reduction of the material flow between the production machines, which leads to a reduction in processing time and logistics, and an enhancement of manufacturing quality due to the processing in one setting. In addition to this approach new processing technologies such as laser-assisted machining are possible.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.235-236
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• 2006

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.332-338
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• 1999

Surface hardening of plain carbon steel (SM$%C) by Laser are usually much finer and stronger than those of the base metals. The present study was undertaken to investigate the wear resistance and a processing parameters such as, power density, pulse width, defocusing distance, and molten depth for surface modification of plain carbon steel. The wear test was carried out under experimental condition using the wear test device, and in which the annular surfaces of wear test specimens as well as mating specimen of alumina ceramics(Al2O3) was rubbed in dry sliding condition. It is shown that molten depth and width depend on defocusing distance. The wear loss on variation of sliding speed was much in lower speed range below 0.2m/sec and in higher speed range above 0.7m/sec, but wear loss was little in intermediate speed range. It depends on oxidation speed and wear speed.

• KSTLE International Journal
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• v.1 no.1
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• pp.12-20
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• 2000

Nano-wear and friction of carbon overcoated laser-textured and mechanically-textured computer hard disk were characterised after contact start/stop (CSS) wear test. Various analytical and mechanical testing techniques were employed to study the changes in topography, roughness, chemical elements, mechanical properties and friction characteristics of the coating arising from the contact start/stop wear test These techniques include: the atomic force microscopy (AFM), the continuous nano-indentation test, the nano-scratch test, the time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and the auger electron spectroscopy (AES). It was shown that the surface roughness of the laser-textured (LT) bump and mechanically textured (MT) Bone was reduced approximately am and 7nm, respectively, after the CSS wear test. The elastic modulus and hardness values increased after the CSS test, indicating straining hardening of the top coating layer, A critical load was also identified fer adhesion failure between the magnetic layer and the Ni-P layer, The TOF-SIMS analysis also revealed some reduction in the intensity of C and $C_2$$F_59$, confirming the wear of lubricant elements on the coating surface.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.95-95
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• 2010

자동차 산업에서 차체를 성형하는 프레스 금형 산업은 꾸준히 증가하고 있는 자동차 생산대수와 함께 성장해가고 있으며, 자동차 산업의 국제 경쟁이 심해지고 소비자들의 요구가 다양해짐에 따라 신제품 개발주기에 발맞추어 금형의 제작에도 단납기 및 비용절감을 위한 노력과 제품의 품질 향상을 위해 신기술, 신공법이 적용되고 있다. 한편 자동차 차체를 제작하는 프레스 금형가공은 박판소재를 원하는 형상으로 제작하는 공정으로써, 프레스의 상 하 운동을 이용하여 강판을 성형한다. 이러한 금형의 형태는 곧 자동차 차체 제품의 형태를 완성하므로 제품을 성형하는 도중에 금형과 소재의 마찰에 의해 금형의 마모나 마멸이 발생하여 제품의 품질을 저하시킬 우려가 있다. 따라서 금형의 내마모성 및 수명을 향상시키기 위한 방안들 중 표면경화처리가 행해지고 있으며, 그중 공정 속도가 빠르고 국부적인 열처리가 가능한 레이저 표면처리 방법이 많은 관심을 받고 있다. 본 연구에서는 이러한 금형의 성질을 향상시키기 위해 고출력 다이오드 레이저를 이용하여 프레스 금형공정 중 드로잉(drawing) 공정에의 적용을 위한 표면경화처리를 실시하였다. 최대출력 4.0kW의 다이오드 레이저를 사용하였으며, 6축 외팔보 로봇에 열처리용 광학계를 장착하여 열처리를 실시하였다. 또한 광학계 부근에는 적외선 온도센서가 부착되어있어 열처리시 시험편의 표면온도를 실시간으로 측정할 수 있도록 구성되어져있다. 시험편은 금형재료용 구상흑연 주철인 FCD550 소재를 사용하였으며, 공정변수에 따른 열처리 특성을 파악하고, 그 경화특성을 평가하였다. 실험 결과, FCD550 소재의 표면 열처리시 레이저 출력 3.5kW, 빔 이송속도 3mm/sec에서 최적의 열처리 특성을 나타내었으며, 이때의 최고 경도는 930Hv을 나타내며 모재에 비해 경도가 3배 정도 상승하는 우수한 경화특성을 보였다.