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권혁우(H. Gwon),허하리(H. L. Hur),구본우(B. W. Gu),김종국(J. K. Kim),강용진(Y. J. Kang),김용석(Y. -S. Kim) 한국소성가공학회 2015 한국소성가공학회 학술대회 논문집 Vol.2015 No.10
Tribological characteristics of a-C:H coating and ta-C coating against AZ31 Mg alloy was investigated. The a-C:H coating was deposited on a STD-61 steel pin by the plasma-enhanced chemical-vapor deposition (PECVD) process. The hydrogen-free DLC (ta-C) was prepared by filtered vacuum arc deposition (FCVA). Dry sliding friction and galling characteristics of the two DLC coatings on the STD-61 steel against AZ31 Mg alloy disks were evaluated using a reciprocating sliding tribometer at room temperature and at 250 ℃. To represent a real sliding during the sheet metal forming process, single-stroke tests were adapted (10 mm of stroke length) rather than a reciprocating long sliding-distance test. Both a-C:H coating and ta-C coating suppressed the adhesion between the Mg alloy and the tool steel at room temperature, which kept the friction coefficient low. However, at 250 ℃, both DLC coatings exhibited severe adhesion to the Mg alloy, which increased the friction coefficient and the galling.
열처리된 2024A1 합금의 석출물이 건식 미끄럼 마멸 특성에 미치는 영향
권혁우(H.W. Gwon),윤나래(N.R. Yoon),김종철(J.C. Kim),정영중(Y.-J. Jung),김용석(Y.-S. Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
In the present study, the effect of precipitates on the dry sliding wear characteristics of 2024 A1 alloy was investigated. Dry sliding wear tests were performed on the as-received (T4) and solution treated 2024 A1 alloy, and their wear behavior was compared in connection with work hardening behavior during the wear. Special attention was given to the relationship between strain hardening and the precipitates, which changed the wear rate and characteristics of the alloy. Work-hardening at the wearing surface is the most important factor during sliding wear of metallic materials, since the strain hardening affects the formation of a deformation layer at the surface. The deformation layer is often related with the formation of wear particles which are detached particles from the layer. The hardened deformation layer also acts as a protecting layer that resists further progress of wear. The relationship between the microstructure and the strain-hardening at the wearing surface was explored, which explained the wear-rate variation with the microstructure.
연마제의 크기와 미세조직에 따른 0.18 wt. % C 탄소강의 3 - body 연삭마멸 특성
윤나래(N. R. Yoon),정영중(Y.-J. Jeong),김종철(J. C. Kim),권혁우(H. W. Gwon),김용석(Y.-S. Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.10
Three-body abrasive wear behavior of 0.18 wt % C steel was investigated using a ball-cratering tester. Silicon carbide of various sizes was used as an abrasive. Wear test conditions were optimized to ensure three-body abrasive wear preventing two-body abrasive wear during the test. The abrasive was supplied as a slurry form, of which the concentration was 0.75 g/ml. Sliding distance, speed (ball-rotation speed) and normal load were fixed as 50 m, 0.05 m/s, and 0.2 N, respectively. Before the abrasive wear test, 0.18 wt % C steel was heat treated under various conditions to vary its microstructure. Effect of the microstructure as well as the abrasive-particle size on the wear was investigated. It was found that the abrasive wear behavior did not depend on a specific parameter such as hardness; besides, the effect of microstructure and abrasive-particle size was significant in determining the wear of the steel.
AISI 52100 베어링강의 미세조직에 따른 3-body 연삭마멸거동
정영중(Y. -J. Jeong),김종철(J. C. Kim),권혁우(H. W. Gwon),윤나래(N. R. Yoon),김용석(Y. -S. Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
This investigation was performed to reveal the microstructural effect on 3-body abrasive wear behavior of the AISI 52100 bearing steel. The steel was heat treated under different conditions to obtain bainite and pearlite microstructures. The bainite and pearlite microstructures were obtained by holding the solution treated specimens at 300℃ and 330℃ for 2 hours and at 650℃ and 700℃ for various period followed by water quenching, respectively. Three-body abrasive wear tests were carried out using a ball-cratering tester. Abrasive slurries of SiC particles (4 fim) suspended in water were used at constant concentration (0.75 g/ml). All tests were performed with a sliding speed of 0.05 m/s, normal load of 0.2 N and sliding distances of 50 m. The slurries were fed on to the top of the ball throughout the test at a rate approximately 1.15 g/min. The worn surfaces were observed by a stereoscopic microscope, SEM, and FESEM (field emission scanning electron microscope). The hardness of specimens was measured by a micro Vickers hardness tester. It was found that the wear resistance of the pearlite was better than that of the bainite.
0.2% C강의 미세조직에 따른 3-body 연삭마멸 특성 연구
윤나래(N. R. Yoon),김종철(J. C. Kim),정영중(J. -Y. Jeong),권혁우(H. W. Gwon),김용석(Y. -S. Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
Abrasive wear behavior of 0.2 wt. % C steel with different microstructures was studied. The steel was heat treated to obtain various microstructures under different conditions. Three-body abrasive wear tests were carried out using a ball-cratering abrasive wear tester at fixed load of 0.2 N. Sliding speed and wear distance adopted were 0.05 m/sec and 50 m, respectively. A bearing steel ball was utilized as a counterpart. SiC particles of size approximately 4 ㎛ were used as the abrasive medium. The slurry concentration and feed rate were 0.75 g/ml and 1.15 g/min, respectively. The wear crater was examined using SEM, FESEM, and a surface profilometer to investigate the wear mechanism of the steel. It was found that the abrasive wear resistance was proportional to initial hardness of the heat treated steel.