• The Journal of Advanced Prosthodontics
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• v.6 no.2
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• pp.138-145
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• 2014

Cobalt-Chromium (Co-Cr) alloys are classified as predominantly base-metal alloys and are widely known for their biomedical applications in the orthopedic and dental fields. In dentistry, Co-Cr alloys are commonly used for the fabrication of metallic frameworks of removable partial dentures and recently have been used as metallic substructures for the fabrication of porcelain-fused-to-metal restorations and implant frameworks. The increased worldwide interest in utilizing Co-Cr alloys for dental applications is related to their low cost and adequate physico-mechanical properties. Additionally, among base-metal alloys, Co-Cr alloys are used more frequently in many countries to replace Nickel-Chromium (Ni-Cr) alloys. This is mainly due to the increased concern regarding the toxic effects of Ni on the human body when alloys containing Ni are exposed to the oral cavity. This review article describes dental applications, metallurgical characterization, and physico-mechanical properties of Co-Cr alloys and also addresses their clinical and laboratory behavior in relation to those properties.

• Journal of the Korean Vacuum Society
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• v.1 no.1
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• pp.106-114
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• 1992

Abstract-Quantitative surface analysis of Co-Ni and Au-Cu alloys by XPS and SIMS was studied. For Co-Ni alloy, quantitative XPS analysis could be done within 1-2% relative error with pure element standards without any correction. For Au-Cu, quantitative XPS analysis was not possible without any correction. But it could be done with standard alloys of various composition within 1-2% relative error. Without standard alloys, Au-Cu alloys could be analyzed by XPS within 10% relative error with pure element standards. For SIMS analysis of Co-Ni alloys, the relative secondary ion yields of Co+/Nit has linear relation with ratio of each composition so that quantitative SIMS analysis was possible for Co-Ni alloys. Preliminary results of XPS round robin test of VAMAS-SCA Japan Project are given.

• Journal of Surface Science and Engineering
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• v.51 no.3
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• pp.139-148
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• 2018

In this study, surface analysis of Ni-Cr and Co-Cr alloys with addition of Ti and Mo for dental CAD/CAM use has been researched experimentally. The surface characteristics of the alloys were examined by Vickers hardness test, bonding strength test, surface roughness test, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction spectroscopy. The shrinkage of the sintered Ni-Cr alloy alloy was slightly larger than that of Ni-Cr-Ti alloy, and larger than Co-Cr alloy. Also, the addition of Mo showed a tendency to decrease shrinkage somewhat. From the result of XRD analysis, NiCr, $Ni_3Cr$ and $Ni_3Ti$ were observed in the sintered Ni-13Cr-xTi and Ni-13Cr-xMo alloys. In addition, ${\sigma}-CrCo$, $Co_2Mo_3$ and $TiCo_2$ were formed in the sintered Co-Cr-xTi and Co-Cr-xMo alloys. Surface hardness of Ti and Mo added alloy was higher than those of Ni-Cr and Co-Cr alloy. The bond strength between sintered alloy and porcelain was $16.1kgf/mm^2$ for Ni-13Cr alloy, $17.8kgf/mm^2$ for Ni-13Cr-5Ti alloy, and $8.2kgf/mm^2$ for Ni-13Cr-10Ti alloy, respectively.

• 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 Korea Foundry Society
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• v.27 no.3
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• pp.120-125
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• 2007

The microstructure, mechanical properties and melting range of Ni-Cr-Mo based alloys were investigated to develop Be-free Ni-Cr-Mo base dental alloys for Porcelain-Fused-to-Metal Firing(PFM). All as-cast alloys showed dendritic structure. Rockwell hardness of 20Cr7Mo was increased with addition of Si and Ti. On the contrary, it was decreased with addition of Co. The duplex alloying elemental addition such as 3Co + xTi, 2Si + xCo and 2Si + xTi to 20Cr7Mo resulted in much increase of hardness. Rockwell hardness and compressive strength for 20Cr3CoSiTi or 17Cr6CoSiTi alloy that add Si-Ti had similar values compared to the commercial alloys. Melting range for 20Cr3CoSiTi and 17Cr6CoSiTi alloy that add Si-Ti showed similar or lower than commercial alloys. In conclusion, 20Cr3CoSiTi and 17Cr6CoSiTi alloys can be applied for commercial use.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.107-107
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• 2015

In order to investigate electrochemical behavior and biocompatibility of Co-Cr dental alloy by electrochemical corrosion test and MTT assay, the xCo-25Cr-yW-zNi alloys were used in this study. Samples of Co-Cr-W-Ni alloys were manufactured using arc melting furnace. The microstructure of the alloys was examined by optical microscopy (OM), Field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), MTT assay, and corrosion test. Corrosion resistance increased slightly as cobalt (Co) content increased. And bioactivity was concerned with nickel (Ni) and tungsten (W). Biocompatibility of Co-Cr alloy depended on Ni and W contents.

• Journal of the Korean Society of Safety
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• v.30 no.4
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• pp.8-13
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• 2015

The magnetic shape memory alloys have recently received a lot of attention due to the considerable progress achieved in understanding the particular importance and the development of the factors. Among these alloys, the ferromagnetic Co-Ni- alloys have been concerned specially because of the thermoelastic character of the fcc (g) - bct (a) martensitic transformation which exhibits under the action of the temperature (shape memory effect), the stress (superelasticity) and the magnetic field (magnetoelasticity). The morphological, the crystallographical, and the thermal characteristics of thermally induced martensite in Co-35.3Ni-11.3Al(wt.%) and Co-28.1Ni-47.4Fe-3.3Ti (wt.%) alloy have been investigated by the scanning electron microscope (SEM), the X-ray Diffraction (XRD), and the differential scanning calorimeter (DSC).

• Journal of the Korean Electrochemical Society
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• v.5 no.1
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• pp.17-20
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• 2002

Various compositions of CoFeNi alloys have been electrodeposited in chloride bath and in sulfate bath, and evaluated for electrodeposition characteristics and magnetic properties. For electrodeposited CoFeNi thin film alloys, the increase of Fe content in the deposits from sulfate bath was considerably faster than those from chloride bath. The current efficiencies in sulfate bath showed observable decrease from $75\%\;to\;50\%$ while those in chloride bath showed no significant decrease. From the low coercivity of 3 Oe in the minimum and the higher squarenesses of the alloys from sulfate bath than those from chloride bath, the alloy at Co, Fe, and Ni contents of $80wt.\%,\;10wt.\%,\;and\;10wt.\%$ can be considered to be the best CoFeNi alloy in this research for the soft magnetic material.

• Korean Journal of Materials Research
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• v.33 no.3
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• pp.95-100
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• 2023

This research examines the effect of adding aluminum on the structural, phasic, and magnetic properties of CoCrFe NiMnAl_x high-entropy alloys. To this aim, the arc-melt process was used under an argon atmosphere for preparing cast samples. The phasic, structural, and magnetic properties of the samples were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrational magnetometry (VSM) analyses. Based on the results, the addition of aluminum to the compound caused changes in the crystalline structure, from FCC solid solution in the CoCrFeNiMn sample to CoCrFeNiMnAl BBC solid solution. It was associated with changes in the magnetic property of CoCrFeNiMnAl_x high-entropy alloys, from paramagnetic to ferromagnetic. The maximum saturation magnetization for the CoCrFeNiMnAl casting sample was estimated to be around 79 emu/g. Despite the phase stability of the FCC solid solution with temperature, the solid solution phase formed in the CrCrFeNiMnAl high-entropy compound was not stable, and changed into FCC solid solution with temperature elevation, causing a reduction in saturation magnetization to about 7 emu/g.

• Journal of Powder Materials
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• v.25 no.3
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• pp.208-212
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• 2018

In this paper, a new $Co_{10}Fe_{10}Mn_{35}Ni_{35}Zn_{10}$ high entropy alloy (HEA) is identified as a strong candidate for the single face-centered cubic (FCC) structure screened using the upgraded TCFE2000 thermodynamic CALPHAD database. The $Co_{10}Fe_{10}Mn_{35}Ni_{35}Zn_{10}$ HEA is fabricated using the mechanical (MA) procedure and pressure-less sintering method. The $Co_{10}Fe_{10}Mn_{35}Ni_{35}Zn_{10}$ HEA, which consists of elements with a large difference in melting point and atomic size, is successfully fabricated using powder metallurgy techniques. The MA behavior, microstructure, and mechanical properties of the $Co_{10}Fe_{10}Mn_{35}Ni_{35}Zn_{10}$ HEA are systematically studied to understand the MA behavior and develop advanced techniques for fabricating HEA products. After MA, a single FCC phase is found. After sintering at $900^{\circ}C$, the microstructure has an FCC single phase with an average grain size of $18{\mu}m$. Finally, the $Co_{10}Fe_{10}Mn_{35}Ni_{35}Zn_{10}$ HEA has a compressive yield strength of 302 MPa.