• Tribology and Lubricants
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• v.38 no.4
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• pp.162-169
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• 2022

Cobalt-chromium (CoCr)-based alloys have been used for wear applications because of their excellent mechanical properties and wear resistance. With growing concern over environmental problems, CoCr alloys are expected to be used for various tribological applications in degraded lubrication states. To expand the applicability of the materials, data should be accumulated across a broad spectrum of experimental parameters. In this work, the friction and wear characteristics of cobalt-chromium-tungsten (CoCrW) and cobalt-chromium-molybdenum (CoCrMo) alloys are investigated experimentally. The tests are conducted using a pin-on-reciprocating-plate tribotester in dry lubrication. CoCrW and CoCrMo are used as pin and plate materials to investigate the effect of the counter material. The results show that the friction coefficients between CoCrW and CoCrMo generally range from 0.4 to 0.5. The friction coefficient between the CoCrW pin and plate is found to be slightly small. However, the total wear between the CoCrW pin and plate is found to be the largest. In contrast, the total wear between the CoCrW pin and plate is relatively small. Furthermore, CoCrW may cause a faster wear progression of CoCrMo, especially for the case in which CoCrMo is used as the pin material. The results of this work provide a better understanding of the tribological properties of CoCrW and CoCrMo alloys. In addition, this work provides a practical guideline for the use of CoCrW and CoCrMo from the tribological design viewpoint.

• The Journal of the Korea Contents Association
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• v.11 no.3
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• pp.293-301
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• 2011

The material of the dental prosthesis was required bio-compatibility for biological, chemical, and physical stabilities. This study was conducted the stability evaluation of mechanical, biological characteristics through comparing Co-Cr alloy(SC group), Ti alloy(ST group) made by the selective laser melting method with Co-Cr alloy(CC group), Ni-Cr alloy(CN group) made by the casting method. Modulus of elasticity for mechanical characteristic evaluation was measured by the tensile test. And we conducted the release material analysis using lactic acid-NaCl solution for the evaluation of biological stability and were observed cytotoxicity through the content of this release medium. Taking these results into account, the Co-Cr alloy made by the selective laser melting method was observed modulus of elasticity higher than he Co-Cr alloy made by the casting method. And the Co-Cr alloy made by the selective laser melting method had more superior biological stability than the other groups as the result of cytotoxicity evaluation through the release material analysis. By this results, we think that alloys made by the selective laser melting method can be applied as materials for making the dental prosthesis.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.5
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• pp.263-267
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• 2017

The Co-Cr as-cast alloys are widely used in the manufacturing of orthopedic implants made with investment casting techniques because of its high strength, good corrosion resistance and excellent biocompatibility properties. Carbide precipitation at grain boundaries and interdendritic regions is the major strenthening mechanism in the as-cast condition. In this study, effects of GPS (Gas Pressured Sintering) heat-treatment on the microstructure and crystallinity of the as-cast Co-Cr alloy prepared by investment casting were investigated. It was confirmed that the content of metal carbide ($Cr_{23}C_6$) was increased in the grain boundary by using optical microscopy (OM), field-emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS).

• Journal of the Korean Magnetics Society
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• v.4 no.2
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• pp.160-167
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• 1994

In order to develop new magnetic media with higher coercivity, we have investigated the magnetic properties of Co-P/Cr and Co-P-Cr/Cr films. The coercivity of Co-P binary films deposited at RT was around 835 Oe in the range of 9-12 at.% P. In the Co-P binary system coercivity decreased with increasing substrate temperature for P contents of 9-12 at.%, which may be due to the decomposition of Co-P single phase to Co and $Co_{2}P$ phase. However, the coercivity of the films containing more than 12 at.% P is very low due to the formation of amorphous phase. The coercivity of Co-P-Cr ternary films increased with increasing Cr contents and reached the maximum value of 1020 Oe in the water $Co_{84}P_{10}Cr_{6}$ Film.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.434-439
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• 2020

Selective laser melting (SLM) manufactures an alloy using laser as a heat source, and has recently been introduced in the dental industry. However, there is a lack of analytical research on metal-ceramic restorations achieved by SLM. This study evaluates and compares the metal-ceramic bond strength of Co-Cr alloys produced by selective laser melting and casting methods. Co-Cr samples required for this study were produced through the sintering process of ceramics, by applying the SLM and CAST methods. The metal-ceramic bond strength was measured by applying the shear bond strength test. In order to determine the area fraction of adherent ceramic, Si content of the specimen was measured using scanning electron microscopy SEM/ EDS. Results of the metal-ceramic bond strength and AFAC were analyzed by t-test (α = 0.05). No significant difference was observed comparing the bond strength of SLM and CAST Co-Cr alloys (P> 0.05). However, the SLM group had much better ceramic adherence than the CAST group (P < 0.001). Moreover, oxidation characteristics were similar for both SLM and CAST Co-Cr alloys, but metal structures were different. These results imply that although the bond of ceramic and Co-Cr alloy is not related to the manufacturing method, SLM alloys impart better ceramic adherence. This indicates that alloys made with SLM can be used to fabricate upper implant prostheses in the future. In particular, it is expected to overcome the shortcomings of the CAST method, and save time and cost.

• Proceedings of the Korean Magnestics Society Conference
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• 1994.03a
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• pp.84-85
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• 1994

• Korean Journal of Materials Research
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• v.7 no.1
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• pp.69-75
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• 1997

Thin films of $Si0_2(1000{\AA})/CoNiCr(400{\AA})/Cr$ were fabricated as a function of Cr thickness by KF magnetron sputtering. The saturation magnetization, coercive force and squareness with annealing temperature for these films were investigated. The values of saturation magnetization of $SiO_2/CoNiCr/Cr$ thin films decreased as the thickness of Cr underlayer increased, whereas coercive force increased as the thickness of Cr underlayer increased. The value of Ms was 600 emu/cc and the maximum value of Hc was 550 Oe. Especially, the value of saturation magnetization was rapidly decreased $SiO_2/CoNiCr/Cr(1700{\AA})$ thin films as the annealing temperature increased And the coercive force increased as the annealing temperature increased When annealing temperature was $650^{\circ}C$, the Ms was reduced to 90 % of the as-deposited film. And the Hc was showed maximum 1600 Oe. It was thought that Cr diffusion into CoNiCr layer reduced the magnetic moment of CoKiCr layer. In addition. Hc might he increased due to grain growth perpendicular to the film plane.

• Tribology and Lubricants
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• v.36 no.4
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• pp.199-206
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• 2020

CoCr-based alloys have been developed as wear-resistant materials owing to their excellent mechanical properties and strong wear resistance. The purpose of this study is to experimentally assess the frictional and wear characteristics of CoCr-based alloys slid against two different counter materials subjected to various normal forces to determine the expansion applicability of CoCr-based alloys. CoCrMo and CoCr alloys were selected as the target materials and NiCr and NiCrB alloys as counter materials. Experimental tests were performed using a pin-on-reciprocating plate tribo-tester under dry lubrication. Before performing the tests, the surface of the specimens was observed through confocal microscopy and the hardness was measured using a micro-Vickers hardness tester. The wear volume of the plate was calculated at the end of the tests using confocal microscope data, and the wear rate was quantitatively obtained based on Archard's wear law. From the results, the wear rates of the CoCrMo specimens that slid against NiCr and NiCrB are 7.69 × 10^-6 ㎣/Nm and 5.26 × 10^-6 ㎣/Nm, respectively. The wear rates of the CoCr specimens that slid against NiCr and NiCrB were higher than those of the CoCrMo specimens by factors of approximately 4 and 8, respectively. The CoCrMo specimens further exhibited lower friction characteristics than the CoCr specimens. The findings of this study will be useful for expanded applications of CoCr-based alloys as wear-resistant materials for various mechanical parts.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.56-62
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• 2008

The biocompatibility and the fatigue strength of Co-Cr-Mo alloy are excellent, so it is used well for the material of artificial joints. The head of artificial joint needs mirror surface for reduction of abrasive resistance. Mirror finishing of Co-Cr-Mo alloy with geometrically defined single crystal diamond cutting tools is handicapped by micro chipping of tool edge. In general, it is said that the micro chipping of diamond tool is caused by work hardening of Co-Cr-Mo alloy for the cut. In the present research, mirror finishing of Co-Cr-Mo alloy by applying ultrasonic elliptical vibration cutting was carried out. The experimental results show that the micro chipping of diamond tool was suppressed and the tool wear was remarkably reduced as compared with the ordinary diamond cutting without elliptical vibration motion. It was confirmed that the good mirror surface of maximum surface roughness of 25 nmP-V was obtained for the cutting length of about 14 m. It is expected that mirror finishing of Co-Cr-Mo alloy can be achieved by applying ultrasonic elliptical vibration cutting practically.

• Journal of Power System Engineering
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• v.9 no.1
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• pp.76-81
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• 2005

The effect of micro-pulse plasma nitriding temperature and time on the case thickness, hardness and nitride formation in the surface of Fe-12Cr-22Mn-X alloy with 3% Co and 1% Ti alloys elements investigated. External compound layer and internal diffusion layer was constituted in plasma nitride case of Fe-12Cr-22Mn-X alloys and formed nitride phase such as ${\gamma}'-Fe4N\;and\;{\varepsilon}-Fe2-3N$. Case depth increased with increasing the plasma nitriding temperature and time. Surface hardness of nitrided Fe-12Cr-22Mn-X alloys obtained the above value of Hv 1,600 and case depth obtained the above value of $45{\mu}m$ in Fe-12Cr-22Mn-3Co alloy and $60{\mu}m$ in Fe-12Cr-22Mn-1Ti alloy. Wear-resistance increased with increasing plasma nitriding time and showing the higher value in Fe-12Cr-22Mn-1Ti alloy than Fe-12Cr-22Mn-3Co alloy.