복합처리 (Carburized/CrN Coating)로 표면개질된 Ti-6Al-4V 합금의 구조 및 피로특성

위명용,박용권 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.12

In order to improve the surface hardness and fatigue of Ti-6A1-4V alloy, plasma carburization and CrN coating were carried out. After composite surface treatment, the depth of carburized layer was about 150 μm and the thickness of CrN coated layer was about 7.5 pm, respectively. Surface hardness and roughness was significantly improved up to about H_(v)1,960 and 0.045 pm after plasma carburized/CrN coating in comparison with the value hardness and roughness, H_(v), 402 and 0.321 μm of the alloy before surface modification. This result might be associated with the formation of TiC carburized layer and CrN coating on the surface of Ti-6A1-4V alloy. During the scratch test of coating, critical load was as high as 32N as compared with the simply processed CrN coating of a 18N. Such changes of hardness and roughness could be contributed to improving the fatigue life. (Received July 14, 2004)

복합처리 (Carburized/CrN Coating)로 표면개질된 Ti-6Al-4V 합금의 구조 및 기계적 성질

박용권,위명용 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.3

In order to improve the low hardness and low wear resistance of Ti-6Al-4V alloy, plasma carburization and CrN coating were carried out. After composite surface treatment, the carburized layer was about 150 ㎛ in depth and CrN coated layer was about 7.5 ㎛ in thickness, respectively. Based on XRD diffraction patterns, preferential growth along (111) direction was observed. The hardness(Hv) was significantly improved up to about 1,960 after plasma carburized/CrN coating while the hardness value of original alloy was 402 before treatment. This result might be associated with TiC carburized layer and CrN coating formation on the surface of Ti-6Al-4V alloy and such high value of hardness dramatically improve the wear resistance. Through the adhesion test of coating, critical load was as high as 32N as compared with the simply processed CrN coating of a 18N.

플라즈마 침탄과 CrN 코팅된 Ti-6Al-4V 합금의 미세구조 및 기계적 특성

박용권,위명용 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.12

In order to improve the low hardness and low wear resistance of Ti-6Al-4V alloy, plasma carburization treatment and CrN film coating was carried out. Effects of the plasma carburization and CrN coating were analyzed and compared with the non-treated alloy by microstructural observation, structural characterization and mechanical property test. The plasma carburization treated alloy formed a carburized layer of about 150 mm in depth from the surface, where a fine and hard particles of TiC and V₄C₃ were evenly homogeneously dispersed through the layer. CrN thin film thickness was about 7.5 mm and grew with (111) orientation. Hardness value of about Hv 402 in the matrix was improved as Hv 1,600, 1,390 by plasma carburization, CrN thin film, respectively. Roughness test is an important method to evaluate the surface treatment effect on the wear resistance. The optimum surface roughness of about 0.063 mm could be obtained by CrN film coated, while, about 0.321 mm and 0.211 ㎛ in the matrix and plasma carburization specimens, respectively.

플라즈마 침탄 및 CrN 코팅된 Ti-6Al-4V 합금의 기계적특성

박용권,위명용 충북대학교 산업과학기술연구소 2002 산업과학기술연구 논문집 Vol.16 No.2

In order to improve the low hardness and low wear resistance of Ti-6Al-4V alloy, plasma carburization treatment and CrN film coating was carried out. Effects of the plasma carburization and CrN coating were analyzed and compared with the non-treated alloy by microstructural observation, structure characterization and mechanical property test. The plasma carburization treated alloy formed a carburized layer of about 150㎛ in depth from the surface, where a fine and hard particles of TiC and V_4C_3 were homogeneously dispersed through the layer. CrN thin film thickness was about 7.5㎛ and grew with (111) orientation. Hardness value of about Hv 402 in the matrix was improved as Hv 1600, 1390 by plasma carburization, CrN thin film, respectively. Roughness test is an important method to evaluate the surface treatment effect on the wear resistance. The optimum surface roughness of about 0.063 ㎛ could be obtained by CrN film coated, while, about 0.321 ㎛ and 0.211 ㎛ in the matrix and plasma carburization specimens, respectively.

Zr-1.5Nb-xSn 합금의 미세조직 및 부식에 미치는 열처리 온도와 Sn 함량의 영향

김영화,위명용,백종혁,정용환 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.2

The corrosion behaviors of Zr-based alloys were investigated with a series of Zr-1.5Nb-xSn ternary alloys which had the variations of β_(Nb) content and final annealing condition. As a result of microstructural study, the _(enriched) was observed in the samples annealed at 640℃, regardless of Sn content. The volume fraction of the precipitates and the Nb concentration in the precipitates did tend to be increased with increasing the Sn content. The samples annealed at 470℃ and 570℃, where β_(Nb) precipitated, exhibited better corrosion resistance than those annealed at 640℃ where β_(Zr) precipitated. The corrosion resistance of the Zr-1.5Nb-xSn alloy system did tend to increase with increasing Sn content. This would be resulted from the reduction of Nb solubility in matrix with increasing Sn content. Thus it eventually facilitate the formation of β_(Nb) phase from the solid solution state of Nb in Zr matrix. The Nb concentration in β_(Nb) phase increased with increasing the Sn content. This would contribute to the formation of β_(Nb) from soluble Nb that existed in the solid solution of Zr matrix.

GaN DFB-레이저다이오드용 회절격자의 제작

김상진,이형규,위명용 충북대학교 컴퓨터정보통신 연구소 2001 컴퓨터정보통신연구 Vol.9 No.1

GaN 에피층을 CCl2F2 와 Ar 가스를 사용한 RIE로 건식각 공정을 개발하여 청색발광용 DFB 레이저 다이오드의 회절격자를 제작하였다. 회절격자의 패턴은 레이저 홀로그래피와 최적조건의 식각 조건 하에서 제작되었다. 얇은 감광제만을 식각 마스크로 사용하면 플라즈마에 의한 마스크 침식에 의해 불규칙적이며 굴곡이 있는 회절격자가 형성되었다. 반면 SiO2/감광제 이중 마스크를 사용하면 마스크 침식 현상이 현저히 감소하여 매우 선명하며 주기적인 격자를 형성할 수 있었다. 제작된 회절격자는 주기 0.25 ㎛, 깊이 약 50nm 인 정현파 형태를 가지고 있었다. We investigated RIE etching parameters of GaN using CCl2F2 and Ar gases and fabricated DFB gratings for the GaN based blue laser diode. Grating patterns were defined by the laser holography followed by RIE etching. Using thin PR as an etch mask, the mask erosion was severe to render the etched pattern rough and aperiodic. However, when SiO2/PR double mask was employed, the mask erosion problem was greatly reduced and a sharp and periodic pattern was obtained. the fabricated grating had a sinusoidal shape with period of 0.25 ㎛ and depth of 50 nm.

아고용한 Zr-Nb 2원계 합금의 미세조직 및 부식특성

林潤洙,崔洋鎭,河憲永,魏明鏞 大田産業大學校 2000 한밭대학교 논문집 Vol.17 No.1

Effect of niobium content on the microstructure and corrosion characteristic of hypo-solubility in binary Zr-Nb alloys were studied. The specimens with 0.2 and 0.4wt.% of niobium were prepared under various annealing temperatures from 400℃ to 800℃ and times from 30 to 5.000 minutes after vacuum arc remelting. The microstructures behavior was observed by a polarized optical microscope. TEM and micro-vickers hardness tester. The recrystallization temperature of the alloys slightly increased with niobium content due to increase of activation energy. The grain growth of the alloys more 0.2 than 0.4 wt.% of niobium occured rapidly. The specimens for corrosion test were prepared by annealing with 590℃ for 2hr to be recrystallized and performed in distilled water at 360℃ using a static mini-autoclave and the corrosion characteristic was measured by weight gains with exposure time. With increasing Nb content from 0.2 to 0.4wt.% the corrosion resistance in Zr-xNb binary alloys decreased an d oxide structure was slowly transformed from tetragonal -ZrO2 to monoclinic-ZrO2.

열처리시 냉간가공된 Zircaloy-4합금의 미세조직 및 재결정 거동

林潤洙,崔洋鎭,鄭蓮眺,魏明鏞 大田産業大學校 1999 한밭대학교 논문집 Vol.16 No.1

Effects of heat-treatment on the microstructure and recrystallization behavior of cold-worked Zircaloy-4 were studied. We used 70% cold-rolled, thin strip specimens. Heat-treatment of the specimens were performed at temperatures between 300℃ and 800℃ for 30 to 5,000 minutes. The recrystallization behavior were observed by means of polarized optical microscopy and TEM. Hardness were measurement by Micro-victors hardness tester. As the annealing time increased, the temperature region of hardness drop moved to lower, because the recovery and recrystallization could occur in lower temperature. The recrysatllization of cold-worked Zircaloy-4 alloys was completed between 500℃ and 600℃ for 60 min. The size of recrystallized grain visibly increased at 800℃ for above 600 min. The activation energy(Q) for recrystallization of Zircaloy-4 alloys was determined by the time for constant fraction technique and it was 253KJ/mo1.

가공된 층상조직의 구상화 속도의 해석

위명용 ( Myeong Yong Wey ) 한국열처리공학회 1991 熱處理工學會誌 Vol.4 No.2

The spheroidization of cold rolled lamellar pearlite in annealing at the temperatures bwtween 600 and 700℃ has been studied by quantitative micrography. It was foud that the spheroidization proceeded as two stageh. The first stage was the stage of relieving the stored energy by cold work, the second was the stage of reducing the interface energy between ferrite and cementite. The spheroidization rate combining the spheroidization rate of each stages is described by the following equation : d(1/S)/dt=k₃·D/_(1/s){σV/_(1/s)+k₄·exp(-bt)} Where, S is the total area of the interface between ferrite and cementite per unit volume, D is the diffusion coefficient, Q is the boundary energy, V is the volume fraction of the cementite, and k₃, k₄, b are constants.

고 망간강 2상 혼합조직의 열적 안정성에 관한

위명용 ( Myeong Yong Wey ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.1

The thermal stability of duplex high Mn-steel structure have been investigated using 15%Mn-1.0%∼2.4%C steels which are composed of γ- and θ-phases in the range of temperature from 900 to 1100℃, and time from 50 to 300h. The results are as follows ; 1) The grain growth in single-phase region proceeds by grain boundary migration and the relation between mean radius r-￣ and annealing time t is described as follows ; r￣^(-2)-r￣^(-2)_0=k_0·t 2) The grain growth of duplex, (γ+θ) , strucrure is slower than that single phase because the chemical composition of γ- and θ-phases differs esch others. 3) The grain of (γ+θ) duplex structure grow slowly in a mode of Ostwald ripening. Because grain boundaries of γ-phase migrate under a restriction of pinning by θ-phases. 4) In the duplex structures, the dispersed structures change to the dual-structures, as the volume fraction of the dispersed second-phase increase. Consequently, the growth-law, which is controlled by boundary-diffusion change to that of the volume diffusion-mechanism.