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김재윤,김경식,김석윤 ( J . Y . Kim,K . S . Kim,S . Y . Kim ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.4
The direct reaction method has been used for the fabrication of Al-Mg/Al₂O₃functionally gradient materials. It was found that the reaction layer of the Al-Mg/Al₂O₃powder compact at 900℃ under air atmosphere led to the formation of reaction layers with varying ceramic phase contents. As the results of experiments by using the TGA system, the characteristics and growth behavior of the reaction layers were affected by the reaction temperature, the gas flow rate, the Mg contents and the Al₂O₃contents.
미끄럼 거리에 따른 STS 304 스테인리스강의 마멸기구 변화
김재윤(J. -Y. Kim),권혁우(H. Gwon),정영중(Y. -J. Jeong),김고남(G. Kim),김명곤(M. G. Kim),김용석(Y. -S. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
In this paper, sliding wear tests of the 304 stainless steels were performed at room temperature varying sliding distance and applied load using a pin-on-disk wear tester. Worn surfaces and wear debris were analyzed using an XRD and observed by an SEM. Micro Vickers hardness was also measured as a function of depth from the worn surface to evaluate work hardening during the wear. Test results showed that the wear mode changed from mild wear to severe plasticity dominated wear (metallic particle oxidation, adhesive wear) as the sliding distance and the applied load increased. The change in the wear mechanism was associated with subsurface plastic deformation and work-hardening. Strain-induced martensitic transformation was observed on the sliding surface of the austenitic stainless steel. Relationship between the transformation and the work-hardening was explored and discussed.
0.3 wt.% C 탄소강 미세조직 시멘타이트 형상에 따른 3-body 연삭마멸 기구 변화
정영중(Y. -J. Jeong),권혁우(H. Gwon),김고남(G. Kim),김재윤(J. -Y. Kim),김명곤(M. G. Kim),김용석(Y. -S. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
The present investigation was performed to figure out the effect of cementite morphology on 3-body abrasive wear characteristics in a 0.3 wt. %C steel. The steel was heat treated under different conditions to have PF/P (Polygonal ferrite & Pearlite), PF/SP (Polygonal ferrite & Spheroidized pearlite), and TM (Tempered martensite) microstructures. Three body abrasive wear tests were carried out using a ball-cratering tester. AISI52100 steel ball was used as a counterpart. The ball-surface was roughened prior to the test, which was necessary for steady feeding of abrasive slurry into the contact between the ball and the specimen. The slurry was composed of Al₂O₃) particles (4 ㎛) suspended in water with a concentration of 0.75 g/㎖. The slurry was fed on top of the rotating ball throughout the test at the rate of 1.445 g/min. All tests were performed at a normal load of 0.2 N, sliding (ball rotation) speed of 0.1 ㎧ and sliding distance of 50 m. Microstructure of the heat treated specimens was observed by an optical microscope, and the worn surfaces were observed by a stereoscopic optical microscope and an SEM (scanning electron microscope). The PF/P (polygonal ferrite/pearlite) specimen displayed high wear resistance, where the wear proceeded by a ploughing mechanism.
금형 강 표면 처리에 따른 AZ31B 마그네슘 합금 판재 Galling 거동의 변화
권혁우(H. Gwon),정영중(Y. -J. Jeong),김고남(G. Kim),김재윤(J. Y. Kim),김명곤(M. G. Kim),김용석(Y. -S. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
In this study, tribological phenomena and galling mechanisms of tool steel coated with various coatings (DLC, CrN and TiN) were examined during sliding against AZ31 B Mg alloy. Reciprocating sliding of the coated tool steel against the Mg alloy plate was carried out at various temperatures under an un lubricated condition. The galling behavior was evaluated by measuring friction coefficient and surface roughness together with SEM observation. Higher and severely fluctuating friction coefficient (stick-slip oscillations) was measured when the Mg particles are transferred from the alloy plate to the tool steel surfaces. DLC coating showed improved anti-galling properties at room temperature during the sliding. However, at high temperature, the coating did not reduce galling and related tribological interactions between the coated steel and the Mg alloy. CrN and TiN coatings showed poor galling characteristics at room temperature compared with uncoated tool steels.