• Journal of Power System Engineering
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• v.12 no.3
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• pp.66-71
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• 2008

Diamond-like-carbon (DLC) coatings could be good candidates as solid lubricants for cutting tools in dry machining of aluminum alloy. In this work, DLC thin films were produced as a friction reduction coating for WC-Co insert tip using the plasma immersion ion beam deposition (PIIED) technique. DLC coatings were also coated on $Al_2O_3$ specimens and high temperature wear tested up to $400^{\circ}C$ in dry air to observe the survivability of the DLC coating in simulated severe cutting conditions using a pin-on-disc tribotester with Hertzian contact stress of 1.3GPa. It showed reduced friction coefficients of minimum 0.02 up to $400^{\circ}C$. And cutting performance of DLC coated WC-Co insert tips to Al 6061 alloy were conducted in a high speed machining center. The main problems of built-up edge formation in aluminum machining are drastically reduced with improved surface roughness. The improvements were mainly related to the low friction coefficient of DLC to Al alloy and the anti-adhesion of Al alloy to WE due to the inertness of DLC.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.89-94
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• 2003

Hard coatings are known to improve the performance of cutting tools in aggressive machining applications, such as high speed machining. New superhard Ti-Al-Si-W films, characterized by a nanocomposite nano-sized (Ti,Al,Si)N crystallites embedded in amorphous $Si_3 N_4$ matrix, could be successfully synthesized on WC-Co substrates by a hybrid coating system of arc ion plating(AIP) and sputtering method. The hardness of Ti-Al-Si-N film increased with incorporation of Si, and had the maximum value ~50 GPa at the Si content of 9 at.%, respectively. And the X-ray diffraction patterns of Ti-Al-Si-N films with various Si content is investigated. In this study, Ti-Al-Si-N coatings were applied to end-mill tools made of WC-Co material by a hybrid coating system. Cutting tests fir the high-hardened material (STD11,$H_R$)C62 and their performances in high speed cutting conditions were studied. Also, the tool wear and tool lift of Ti-Al-Si-N with various si(6, 9, 19) contents were measured.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.178-181
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• 2005

Quaternary Ti-Si-C-N coatings were deposited on WC-Co substrates by a hybrid coating system of arc ion plating (AIP) and sputtering techniques using Ti and Si targets, in an $Ar/N_2/CH_4$ gaseous mixture. The crystallinity, bending status, and microstructure of the Ti-Si-C-N coatings were measured by X-ray diffractometer (XRD) and X-ray photoelectron spectroscope (XPS), The micro-hardness of Ti(C,N) and Ti-Si-N coatings were about 30 and 40 GPa, respectively. As the Si was incorporated into Ti(C,N) coatings, the Ti-Si-C-N coatings having Si content of $8.9\;at.\%$ showed the maximum hardness value of about 55 GPa. In this work, the microstructure and mechanical properties of Ti-Si-C-N coatings were systematically investigated.

• Journal of the Korean institute of surface engineering
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• v.41 no.6
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• pp.292-300
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• 2008

Dental implant system is composed of abutment, abutment screw and implant fixture connected with screw. The problems of loosening/tightening and stability of abutment screw depend on surface characteristics, like a surface roughness, coating materials and friction resistance and so on. For this reason, surface treatment of abutment screw has been remained research problem in prosthodontics. The purpose of this study was to investigate the stability of TiN and WC coated dental abutment screw, abutment screw was used, respectively, for experiment. For improving the surface characteristics, TiN and WC film coating was carried out on the abutment screw using EB-PVD and sputtering, respectively. In order to observe the coating surface of abutment screw, surfaces of specimens were characterized, using field emission scanning electron microscope(FE-SEM) and energy dispersive x-ray spectroscopy(EDS). The stability of TiN and WC coated abutment screw was evaluated by potentiodynamic, and cyclic potentiodynamic polarization method in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The corrosion potential of TiN coated specimen was higher than those of WC coated and non-coated abutment screw. Whereas, corrosion current density of TiN coated screws was lower than those of WC coated and non-coated abutment screw. The stability of screw decreased as following order; TiN coating, WC coating and non-coated screw. The pitting potentials of TiN and WC coated specimens were higher than that of non-coated abutment screw, but repassivation potential of WC coated specimen was lower than those of TiN coated and non-coated abutment screws due to breakdown of coated film. The degree of local ion dissolution on the surface increased in the order of TiN coated, non-coated and WC coated screws.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.104-104
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• 2016

음극아크증착과 스퍼터링을 동시에 사용한 하이브리드 공정으로 제조된 TiAlSiN 코팅층의 물성을 평가하였다. TiAlSiN 코팅층은 음극아크 소스에 Ti-Al 타겟을 장착하고 스퍼터링 소스에는 Si 타겟을 장착하여 아르곤과 질소 가스의 혼합가스 분위기에서 스테인리스(SUS304)와 초경(cemented carbide; WC-15wt.%Co) 기판 위에 제조되었다. 음극아크 소스에 인가되는 전류는 고정하고 스퍼터링 소스에 인가되는 전력을 조절하여 TiAlSiN 코팅층의 Si 함량을 제어하였다. TiAlSiN 코팅층의 Si 함량이 증가하면 코팅층의 구조가 주상정에서 비정질 구조로 변화한다. 이는 Si 함량이 증가하면 코팅층에 형성되는 알갱이 구조의 크기가 줄어들기 때문이다. X-선 회절 결과와 Scherrer's equation을 이용하여 Si 함량에 따른 알갱이 구조의 크기를 계산하면 Si이 없는 코팅층은 약 14 nm의 크기를 보이며 8 at.% 이상의 함량에서 약 2.5 nm로 포화된다. TiAlSiN 코팅층의 경도를 Si 함량에 따라 측정하면 Si 함량이 증가하면 경도도 증가하는 경향을 보이며 약 9 at.%의 Si 함량에서 3200 Hv로 최대가 되고 이후에는 감소한다. TiAlSiN이 코팅된 스테인리스 시편을 대기에서 열처리하고 시편 무게증가를 측정하여 코팅층의 내열성을 평가하였다. Si 함량이 증가하면 내열성도 향상되는데 14.4 at.%의 Si 함량에서 $700^{\circ}C$까지 무게 증가가 없으며 $900^{\circ}C$까지 0.43 mg의 증가를 보인다. 본 실험을 통해서 얻어진 TiAlSiN 코팅층은 비교적 높은 경도와 내열성을 확보하여 절상공구 보호막 코팅 소재 등으로 활용이 가능할 것으로 판단된다.

• Journal of Welding and Joining
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• v.32 no.6
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• pp.41-46
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• 2014

In this study, cracking susceptibility of laser cladding was investigated according to the processing parameters such as laser power, scan speed and feeding rate with blended powders of stellite#6 and technolase40s (WC+NiCr). The solidification microstructure of clad was composed of Co-based dendrite structures with ${\gamma}+Cr7C3$ eutectic phases at the dendritic boundaries. The crack propagation showed transgranular fracture along dendritic boundaries due to brittle chrome carbide at the eutectic phases. From results of fractography experiments, the fracture surface was typical cleavage brittle fracture in the clad and substrate. The number of clad cracks, caused by a tensile stress after the solidification, increased with increase of laser power, scan speed and feeding rate. Increase of the laser power caused large pores by facilitating WC decarburizing reaction. And the pores affected increase of crack susceptibility. High scan speed caused increment of clad cracks due to thermal stress and WC particle fractures. Also, increase of the feeding rate accompanied an amount of WC particles causing crack initiation and decarburizing reaction.

• Korean Journal of Materials Research
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• v.29 no.1
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• pp.52-58
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• 2019

The microstructure, hardness, and wear behaviors of a High Velocity Oxygen Fuel(HVOF) sprayed WC-CoFe coating are comparatively investigated before and after laser heat treatments of the coating surface. During the spraying, the binder metal is melted and a small portion of WC is decomposed to $W_2C$. A porous coating is formed by evolution of carbon oxide gases formed by the reaction of the free carbon and the sprayed oxygen gas. The laser heat treatment eliminates the porosity and provides a more densified microstructure. After laser heat treatment, the porosity in the coating layer decreases from 1.7 % to 1.2 and the coating thickness decreases from $150{\mu}m$ to $100{\mu}m$. The surface hardness increases from 1440 Hv to 1117 Hv. In the wear test, the friction coefficient of coating decreases from 0.45 to 0.32 and the wear resistance is improved by the laser heat treatment. The improvement is likely due to the formation of oxide tribofilms.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.5
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• pp.262-269
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• 2022

In order to process materials such as engineering plastics, which are difficult to mold due to their high strength compared to conventional polymer materials, it is necessary to improve the hardness and strength of parts such as screws and barrels of injection equipment in extrusion system. High-velocity oxygen fuel (HVOF) process is well known for its contribution on enhancement of surface properties. Thus in this study, using the HVOF process, WC coating layers of different thicknesses were bonded to the surface of S30C substrate by controlling the movement speed of the spray nozzle and each property was evaluated to decide the optimization condition. Through the results, the thickness of WC coating layer increased from 0 to 200 ㎛ maximum, along with the decrement of nozzle movement speed and the surface hardness get increased. Especially, the coated layer with the thickness over 180 ㎛ under the nozzle speed 500 mm/s had high hardness than thinner layer. In addition, the amount of wear consumed per unit time was also significantly reduced due to the formation of the coating layer.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.161-162
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• 2009

하이브리드 코팅장비를 이용해 WC-CO기판위에 Ti-Si-N박막을 증착 시켰다. 이 연구는 Ti-Si-N박막의 기계적 성질에 온도와 바이어스가 미치는 영향에 대해 실험을 하였다. 증착온도가 $300^{\circ}C$까진 Ti-Si-N박막의 미세경도와 탄성률은 증가했지만 증착온도가 $300{\sim}350^{\circ}C$에서는 탄성률은 감소하고 결정 성장으로 인해 미세경도는 감소하였다. 기판 바이어스는 박막과 미세구조에 압축 잔류 응력을 야기 시킨다. 그러나 기판바이어스가 -400V 이상에서는 re-sputtering에 의해 Si함량이 감소한다. Ti-Si-N 박막의 가장 우수한 기계적 성질은 $300^{\circ}C$, -100V에서 얻을 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.27-36
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• 2019

The demand for a low dispersion lens with a small refractive index and a high refractive index is increasing, and accordingly, there is an increasing need for a releasable protective film with high heat resistance and abrasion resistance. On the other hand, the optical industry has not yet established a clear standard for the manufacturing process and quality standards for mold-releasing protective films used in aspheric glass lens molding. Optical lens manufacturers treat this technology as proprietary information. In this study, an experiment was conducted regarding the optimization of ion etching, magnetron, and arc current at each source and filter part, and bias voltage in FCVA (filtered cathode vacuum arc)-based Ta-C thin film coatings. This study found that compared to iridium-rhenium alloy thin film sputtering products, the coating conditions were improved by approximately 50%, 20%, and 40% in terms of thickness, hardness, and adhesive strength of the film, respectively. The thin-film coating process proposed in this study is expected to contribute significantly to the development and utilization of glass lenses, which will help enhance the minimum mechanical properties and quality of the mold-release thin film layer required for glass mold surface forming technology.