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플라즈마 침탄 및 CrN 코팅된 Ti-6Al-4V 합금의 구조 및 Creep특성
위명용,박용권,Wey Myeong-Yong,Park Yong-Gwon 한국재료학회 2004 한국재료학회지 Vol.14 No.8
In order to improve the low hardness and low wear resistance of Ti-6Al-4V alloy, plasma carburization treatment and CrN film coating were carried out. Effects of the plasma carburization and CrN coating were analyzed and compared with the non-treated alloy by mechanical and creep tests. After plasma carburization and CrN coating treatments, the carburized layer was about 150 ${\mu}m$ in depth and CrN coated layer was about 7.5 ${\mu}m$ in thickness. Hardness value of about $H_{v}$ 402 of the non-treated alloy was improved to $H_{v}$ 1600 and 1390 by plasma carburization and CrN thin film coating, respectively. Stress exponent(n) was decreased from 9.10 in CrN coating specimen to 8.95 in carburized specimen. However, the activation energy(Q) was increased from 242 to 250 kJ/mol. It can be concluded that the static creep deformation for Ti-6Al-4V alloy is controlled by the dislocation climb over the ranges of the experimental conditions.
위명용,장곡부 광홍 ( Wey Myeong Yong,Hasebe Mitsuhiro ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.2
In order to elucidate thermal stability of Fe-Fe₂Ti eutectic structure, the initial several structures have been investigated in the changes of coarsening and spheroidization during prolonged annealing under the eutectic temperature. The results are as follows: 1) The rate constant of coarsening and spheroidization was formulated as S^(-n)-S^(-n)_0=k·t, where S is the total area of the interface between α and C(Fe₂Ti) per unit volume, S_0 is initial value and k is the rate constant. 2) The coarsening and spheroidization mechanism was described by Ostwald ripening and controlled by diffusion of Ti-atom in α-phase. 3) The spheroidization rate constant in eutectic lamellar structures was depended upon annealing temperature and showed the Arrhenius relation. The activation energy for spheroidization of lamellar structure was 365 kJ/mole.
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.
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.
박용권(Yong Gwon Park),최재하(Jae Ha Choi),위명용(Myeong Yong Wey) 한국열처리공학회 2002 熱處理工學會誌 Vol.15 No.4
N/A The steady-static creep behaviors of Ti-6Al-4V alloy, using the constant stress creep tester, were investigated over the temperature range of 510∼550℃(0.42-0.44Tm) and the stress range of 200-275 MPa(20.41∼28.06 ㎏/㎟). The stress exponents(n) for the static creep deformation of this alloy were 9.85, 9.35, 9.24 and 8.85 at the temperature of 510, 525, 535 and 550℃, respectively. The stress exponent(n) decreased with increasing the temperature and became close to about 5. The apparent activation energies(Q) for the static creep deformation were 254.4, 241.8, 234.4 and 221.9 kJ/mole for the stress of 200, 225, 250 and 275MPa, respectively. The activation energy(Q) decreased with increasing the stress. From the above results, it can be concluded that the static creep deformation for Ti-6Al-4V alloy was controlled by the dislocation climb over the ranges of the experimental conditions. Larson-Miller Parameter(P) for the crept specimens of Ti-6Al-4V alloy under the static creep conditions was obtained as P=(T+460) (log t_T+21). The failure plane observed by SEM showed up dimple phenomenon at all range.
CrN 박막처리된 Ti-6Al-4V 합금의 기계적 성질과 피로특성
박용권,백창현,위명용,Park, Yong-Gwon,Baeg, Chang-Hyung,Wey, Myeong-Yong 한국재료학회 2002 한국재료학회지 Vol.12 No.8
CrN film coated by AIP method, improved the mechanical properties (Hardness, Roughness, wear and fatigue) of Ti-6Al-4V alloy. The properties were studied using GXRD, XPS, Hardness, Roughness, wear and fatigue testers. CrN thin film thickness was about 7.5$\mu\textrm{m}$ and grew with (111) orientation. Hardness of CrN thin film was very high (Hv 1390) and roughness of the surface layer was greatly improved (Ra=0.063$\mu\textrm{m}$) compared with matrix alloy (Ra=0.321$\mu\textrm{m}$). Such changes of hardness and roughness could be contributed to improving the wear resistance and fatigue life. Striation like pattern with dimples and voids, a typical fatigue fracture mode, was observed throughout the specimen.
백창현,박용권,위명용,Park, Yong-Gwon,Park, Yong-Gwon,Wey, Myeong-Yong 한국재료학회 2002 한국재료학회지 Vol.12 No.8
Microstructure, mechanical properties, and oxidation resistance of TiAIN thin films deposited on quenched and tempered STD61 tool steel by arc ion plating were studied using XRD, XPS and micro-balance. The TiAIN film was grown with the (200) orientation. The grain size of TiAIN thin film decreased with increasing Al contents, while chemical binding energy increased with Al contents. When hard coating films were oxidized at $850^{\circ}C$ in air, oxidation resistance of both TiN and TiCN films became relatively lower since the surface of films formed non-protective film such as $TiO_2$. However, oxidation resistance of TiAIN film was excellent because its surface formed protective layer such as $_A12$$O_3$ and $_Al2$$Ti_{7}$$O_{15}$, which suppressed oxygen intrusion.
Ti-6Al-4V 합금의 미세조직 및 기계적 특성에 미치는 Plasma 침탄 처리의 영향
박용권,김택수,지태구,위명용,Park, Yong-Gwon,Kim, Taek-Su,Ji, Tae-Gu,Wey, Myeong-Yong 한국재료학회 2002 한국재료학회지 Vol.12 No.5
In order to improve the low wear resistance of Ti-6Al-4V alloy, plasma carburization treatment was newly carried out without consumption of its good specific strength and fatigue life over the temperature. Effect of the plasma carburization was analyzed and compared with the non-treated alloy by microstructural observation, structure characterization and mechanical property test. The plasma treated alloy formed a carburized layer of about 150$\mu\textrm{m}$ in depth from the surface, where a fine and hard particles of TiC and $V_4C_3$ were homogeneously dispersed through the layer. It was also found that an increase of the wear resistance, fatigue life and hardness, due to the hard and fine dispersoids.