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PECVD 에 의해 형성된 TiCN 박막의 형상 및 밀착성
허정(J. Huh),남태운(T. W. Nam) 한국열처리공학회 2002 熱處理工學會誌 Vol.15 No.3
N/A TiCN thin films were deposited on tool steels at 510℃ by PECVD from a TiCl_4+N_2+CH_4+H_2+Ar gaseous mixture. The microstructures and preferred orientation were investigated. The micro-scratch tests were performed using a system equipped with an acoustic emission sensor. Critical loads were determined to evaluate the adhesion of TiCN to substrate. The influences of the microstructures of substrates, double layered coatings, and coatings after nitriding(duplex coating) were investigated. The experimental results showed that the microstructures of substrates and double layered coating did not affect the critical loads considerably. By the duplex coating, critical loads were not always increased. In some cases, duplex coatings decreased critical loads significantly despite of absence of black layer. In this study, we tried to relate the results of scratch test to the residual stress analysis. Nitriding before the coating reduces the tensile residual stress in the film, which gives rise to low critical load in scratch test.
허정(J. Huh),유용주(Y. Z. You) 한국열처리공학회 2002 熱處理工學會誌 Vol.15 No.3
BCl_3를 봉소의 공급원으로 하여 공구강의 표면에 PECVD 방식에 의해 TiBN 박막을 코팅하였다. TiBN박막의 미세조직은 TiN에 비해 상대적으로 치밀하여 Hv 5000이상의 고경도를 얻을 수 있었다. 박막의 경도와 밀착력은 BCl_3양에 따라 증가하여 41/h일 때 최대치를 나타냈는데 내마모성도 이 때가 가장 우수하였다. TiBN 코팅에 의해 금형의 수명을 크게 향상시킬 수 있었고 특히 다이캐스팅 금형에서 그 효과가 크게 나타났다. During warm and hot forging process of steels or aluminum alloys, dies are subject to earty fracture, severe wear by thermo-mechanical stress. Especially, during the die-casting of aluminum alloys, the service life of dies is incredibly lowered. In this study we investigated the characteristics of TiBN films produced by PECVD. TiBN films showed very high hardness, excellent wear resistance, which could enhance the service life of die parts such as forging punch, die casting core pin successfully.
VCM강판 성형성을 위한 하이브리드 코팅에 미치는 중간층의 영향
임형철(H. C. Lim),오상균(S. K. Oh),권태하(T. H. Kwon),서창희(C. H. Suh),장원석(W. S. Jang),정윤철(Y-C. Jung),허정(J. Huh) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
This study was carried out to investigate the properties of DLC coating layer according to the inter-layer when the hybrid coating is applied to dies for VCM sheet forming. It is the hybrid coating that the inter-layer and DLC are successively coated on surface of the base material. And various conditions of the inter-layer affect the DLC coating layer. So Vickers hardness test, scratch test, friction test and roughness measurement are performed in order to check the effect of the inter-layer such as VC, TiAlN, Cr and CrN and whether or not doping of N2 gas is applied. Also, it is analyzed that the correlation between the bonding force and other parameters such as the hardness, roughness and doping of N₂. As a result, it is found that properties of DLC coating layer are better than something else, when the inter-layer is CrN without doping of N₂ gas.
오스테나이트계 스테인리스강에 대한 질소 고용화 처리 및 그 효과
남태운,허정 한국열처리공학회 2000 熱處理工學會誌 Vol.13 No.5
As a case hardening process for stainless steels, nitriding is more preferred and widely used than carburizing which deterioates corrosion resistance severely. In order to add the nitrogen into the stainless steels, passive film on the surface must be removed effectively before nitriding. Conventional gas nitriding process is performed in the temperature range of 500 to 600℃ with NH₃ gas, which often leads to sensitization of stainless steels. In this study, we tried to activate passive film of austenitic stainless steels by heating at low pressure.(900℃, 5×10^(-2) Torr.) Nitriding was performed at the solution treatment temperature of 1100℃ with nitrogen molecules instead of NH₃gas. An attainable nitrogen content in a case depends on the nitrogen gas pressure at constant nitriding temperature. A case depth is proportional to the square not of solution time, which suggests that inward diffusion of nitrogen follows the Fick's 2nd law. Surface nitrogen atoms are dissolved as interstitial solutes, or precipitated in the form of MN, M₂N nitrides, which increase the case hardeness. Dissolved nitrogen in the case enhances the cavitation resistance of austenitic stainless steels dramatically.