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CNx 코팅된 강의 회전접촉피로에 미치는 코팅두께의 영향
최병영,Umehara, Noritsugu 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.5
Ion beam assisted deposition system was used to deposit CNx coatings with various thickness on the substrates of high-frequency induction hardened steels. Rolling contact fatigue tests were performed using Polymet RCF-1 machine with a constant supply of lubricant. Rolling contact fatigue life was substantially different in the steels with various thickness of CNx coatings. The optimum thickness of CNx coating was found to be 8.9㎛, showing the longest fatigue life, mainly caused by higher resistance to initiation of cracks and protective overcoat remaining to the surface failure during rolling contact fatigue. Cracks were initiated in the substrates under the surface of wear track and propagated to the surface, which eventually resulted in the failure. The reduction of fatigue life observed in the specimen with elimination of CNx coating during rolling contact fatigue was explained by the substrates deformation.
최병영,Umehara, Noritsugu,Kato, Koji 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.9
Carbon nitride thin films were deposited on the substrates of 0.55wt%C-1.68wt%Mn induction-hardened steels by ion beam assisted deposition. Rolling contact fatigue tests were conducted using Polymet RCF-1 machine under elastohydrodynamic lubricating condition at room temperature. Failure modes during rolling contact were investigated on the basis of surface and subsurface observations of the failed coated steels. Many micropits were formed on the creater surface of wear track of the coated steels in the wedge forming mode. Subsurface cracks were initiated at the relatively large oxide inclusions and propagated in the intergranular fracture mode. It was also found in the surface of wear track after the substrate deformation during repeated rolling contact that Carbon and Oxygen elements of the coating were retained. It was suggested on the basis of the experimental results that failures during rolling contact of the steels were delayed or protected by carbon nitride coating of the steels with smaller oxide inclusions and finer grains.
김종형,Noritsugu Umehara,Hiroyuki Kousaka,Mamoru Shimada,Mitsuru Hasegawa 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1
Adhesion between rubbers and metals is often the main cause of machine trouble. Therefore, efficient utilization of rubber in dynamic and static applications requires the modification of the adhesion property of the rubber surface without affecting the bulk characteristics. In this work, we have studied the mechanism of the reduction in adhesion force between medical rubber, chloride-isobutene-isoprene rubber (CIIR), and stainless steel by using surface wave-excited plasma treatment of the rubber surface with oxygen and argon gases. Experimental results showed that surface roughness derivations increased by about 10 times across the treatment, at maximum, corresponding to the increase in time. In addition, the micro-scale Young’s modulus of treated CIIR sheet increased by about 6.3 times at maximum from that of the untreated CIIR sheet. These changes in Young’s modulus and roughness at the surface of CIIR sheet are considered to be the main reasons for the plasma-assisted reduction of adhesion force between stainless steel ball (SUS 440C, JIS) and CIIR sheet.
Hexagonal 배열 40 μm Dimple 패턴의 트라이볼로지적 특성
최원식,채영훈,Noritsugu Umehara 한국트라이볼로지학회 2009 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.25 No.1
본 연구에서는 pin-on-disk 마찰 시험기를 통하여 Hexagonal 배열 40 μm Dimple 패턴의 효과를 실험하였다. 마찰 실험은 미끄럼 속도가 0.06 ~ 0.34 m/s로 하였으며 마찰하중은 20 ~100 N의 범위로 하였고, Dimple의 밀도는 10 ~ 25%의 범위로 제작하여 실험을 행하였다. 일반적으로 속도가 증가하고 하중이 감소할수록 마찰계수는 감소하는 경향을 나타내었으며, Dimple에 의한 마찰저감 효과는 속도가 0.14~ 0.26 m/s의 범위에서 나타났다. 40 μm Hexagonal 배열 Dimple 패턴의 마찰 특성에서는 밀도가 12.5%에서 가장 좋은 경향을 나타내었다.
Friction Characteristics of CNx Coated Dimple Pattern with Hexagonal Array
wonsik Choi(최원식),Noritsugu Umehara 한국트라이볼로지학회 2011 한국윤활학회지(윤활학회지) Vol.27 No.5
In this study, we examined the friction characteristics of a dimple pattern on a carbon nitride coating. The study was conducted with a hexagonal array 40 ㎛ dimple pattern on a steel bearing containing a CNx coating. The area density of the dimple patterns were varied between 5% and 25%, the speed was varied from 0.06-0.26 ㎧, and the load was varied between 20-100N. In general, we found that as the velocity increased, the friction coefficient increased. Furthermore, the friction coefficient was lowest at a load of 40N. The friction coefficient of the non-coated specimen was 0.025-0.15; on the other hand, the friction coefficient of the coated specimen was 0.002-0.02. Thus, we determined that the coated materials could reduce the friction coefficient by a factor of 7.5.