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레이저 쇼크 피닝에 의한 2205 듀플렉스 스테인리스강의 표면 경도 향상과 표면 변화 관찰
임현택(H. T. Lim),정회민(H. M. Jeong),김필규(P. K. Kim),정성호(SungHo Jeong) 한국레이저가공학회 2011 한국레이저가공학회지 Vol.14 No.1
This work reports the results for laser shock peening of duplex stainless steel (22% Chromium - 5% Nickel) using a pulsed Nd:YAG laser (wavelength = 532nm, pulse width = 8ns). for the application to high-capacity pumps for seawater desalination plants. By properly selecting the process parameters such as laser intensity of 10GW/cm2, laser pulse density of 75pulse/mm2, and 100μm thick aluminum foil as an absorbent coating layer, the surface hardness of duplex stainless steel could be enhanced by 26%, from 256HV to 323HV with little changes in surface morphology and roughness. The depth of laser shock peened layer was measured to be around 2mm. The large enhancement of surface hardness is considered to have high practical importance in minimizing abrasive and corrosive deterioration of pump parts.
임현택(H. T. Lim),이명화(M. H. Lee),김필규(P. K. Kim),박종복(J. B. Park),정성호(S. H. Jeong) 한국레이저가공학회 2009 한국레이저가공학회지 Vol.12 No.3
Experimental results for the laser shock peening of stainless steels, duplex stainless steel and STS304, for the enhancement of surface hardness are reported. A high power Nd:YAG laser (532 nm, 2nd harmonics) was used to irradiate the workpiece in water at the irradiances of 5, 10, 15 GW/cm2. The surface of a workpiece was covered with Fe or Al foil for protection of the original surface and reduction of laser reflection. The laser pulse densities were varied from 25 pulse/mm2 to 75 pulse/mm2. In the case of the STS304, the surface hardness increased with increasing pulse density and the maximum increase of about 29% was achieved using Fe foil at 10 GW/cm2 and 75 pulse/mm2 conditions. The maximum increase in surface hardness of duplex stainless steel was about 8% at 10 GW/cm2 and 75 pulse/mm2 with also Fe foil. In the case of the Al foil, less increase of surface hardness was obtained, possibly due to the thermal expansion effect.
임현덕(H. D. Im),오광환(K. H. Oh),임현택(H. T. Lim),정성호(S. H. Jeong) 한국레이저가공학회 2008 한국레이저가공학회 학술대회 논문집 Vol.2008 No.-
An optical fiber-based laser etching technique is used to fabricate microgrooves on stainless steel foil. A nozzle structure that produces an etchant jet is designed and utilized in experiments so that the application of laser etching technique can be extended to arbitrary size workpiece. The fabricated microgrooves can be applied for the wick-structure of micro heat pipes through which the circulation of working fluid occurs by capillary pressure. The capillary pressure of the microgrooves depends on the parameters including working fluid, groove size and shape, and surface roughness, and directly influences on the performance of micro heat pipes. The capillary flow velocity for varying groove parameters is measured to examine the relationship between groove parameters and cooling capacity of micro heat pipes.
레이저유도 에칭을 이용한 고세장비 마이크로채널 가공 및 응용
오광환(Kwang H. Oh),이민규(M. K. Lee),김수근(S. G. Kim),임현택(H. T. Lim),정성호(S. H. Jeong) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월
High-aspect-ratio(max. 12.5) microchannels with excellent surface quality and good shape uniformity have been realized utilizing laser-induced etching technique. Etch width and depth variations depend largely upon process variables such as laser power and etchant concentration. Etchant concentration in association with viscosity also influence on the cross-sectional profile of the channels. The optimum process conditions for the fabrication of high-aspect-ratio microchannels applicable to micro thermal devices are demonstrated.