• Resources Recycling
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• v.27 no.4
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• pp.16-22
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• 2018

Inconel713C which of a commercial Ni super alloy have the compositions of 70 wt.% Ni, 12 wt.% Cr, 6 wt.% Al and 4 wt.% Mo. In this study, solvent extraction has been performed to separate Mo from the synthetic leaching solution, formation of Inconel713C alloy similarly and is found the optimum conditions of recovery of Mo from the leaching solution. The effects of some variables, such as the nature and concentration of the extractants, $H_2SO_4$ concentrations, and the presence of impurities were investigated. The extraction percentage of Mo by Cyanex272 is 96% in the condition of pH 1 and 4% of concentration of Cyanex272 but Alamine336 is 99% in the condition of the range of pH 1 to 4 and 1 wt.% of concentration of Alamine336. In the case of Alamine336, the extraction percentage of Mo is increased by increasing of the concentration of Alamine336. The optimum condition of this experiment is pH 1 in aqueous phase, 1% concentration of Alamine336 and activation ratio of $H_2SO_4$ 1:0.5.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.2
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• pp.178-190
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• 2000

The purpose of this study was to evaluate the surface roughness of Ni-Cr-Be alloy($Verabond^{(R)}$, Aalba Dent Inc., USA) according to electrolyte concentration and etching time. Total of 150 metal specimens ($12{\times}10{\times}1.5mm$) composed of 5 polisded specimens, 5 sandblasted specimens, 140 etched specimens were prepared. Etched groups were divided into 28 groups by the $HClO_4$ concentrations(10, 30, 50, 70%) and etching times(15, 30, 60, 120, 180, 240, 300 seconds). The mean surface roughness(Ra) and the etching depth were measured with Optical 3-dimensional surface roughness measuring machine(Accura 1500M, Intek Engineering Co., Korea) and observed under SEM. The results obtaind were as follows: 1. Surface roughness(Ra) and etching depth were affected by the order of etching time, electrolyte concentration, and their interaction(P<0.05). 2. Surface roughness(Ra) and etching depth were increased with etching time in 10%, 30% electrolyte concentrations, but they had no significant difference with etching time in 70% (P<0.05). 3. Surface roughness(Ra) and etching depth decreased in the order of 30, 10, 50, 70% electrolyte concentrations from 120 seconds etching time(P<0.05). 4. The remarkable morphologic changes in etched surface were observed along the grain boundaries in 15, 30 seconds of 10%, 30% concentrations and the morphologic changes could be denoted in the grains themselves as well as along the boundaries with the lapse of time. Even though the noticeable morphologic changes also took place in etched surface with 50% concentration, the degree of changes were less than that of changes with 10%, 30%. However, there were little morphologic changes with 70% concentration regardless of etching time. 5. Surface roughness(Ra) of sandblasting group with $50{\mu}m\;Al_2O_3$ had no significant difference with 30%-30 seconds etched group(P<0.05).

• Journal of the Korean institute of surface engineering
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• v.40 no.4
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• pp.175-179
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• 2007

An Fe-Ni-Co based superalloy Incoloy 909 (Incoloy 909) has been used for gas turbine engine component material. This alloy is susceptible to high temperature oxidation and corrosion because of the absence of corrosion resistant Cr. For the improvement of durability of the component of Incoloy 909 aluminizing-chromate coating by pack cementation process has been investigated at relatively low temperature of about $550^{\circ}C$ to protect the surface microstructure and properties of Incoloy 909 substrate. As a previous study to aluminizing-chromate coating by pack cementation of Incoloy 909, the optimal aluminizing process has been investigated. The size effects of source Al powder and inert filler $Al_O_3$ powder and activator selection have been studied. And the dependence of coating growth rate on aluminizing temperature and time has also been studied. The optimal aluminizing process for the coating growth rate is that the mixing ratio of source Al powder, activator $NH_4Cl$ and filler $Al_O_3$ are 80%, 1% and 19% respectively at aluminizing temperature $552^{\circ}C$ and time 20 hours.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.6
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• pp.654-663
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• 2004

Statement of problem. According to the fracture pattern in several reports, fractures most frequently occur in the interface between the ceromer and the substructure. Purpose. The aim of this in vitro study was to compare the macro shear bond strength and microshear bond strength of a ceromer bonded to a fiber reinforced composite (FRC) as well as metal alloys. Material and methods. Ten of the following substructures, type II gold alloy, Co-Cr alloy, Ni-Cr alloy, and FRC (Vectris) substructures with a 12 mm in diameter, were imbedded in acrylic resin and ground with 400, and 1, 000-grit sandpaper. The metal primer and wetting agent were applied to the sandblasted bonding area of the metal specimens and the FRC specimens, respectively. The ceromer was placed onto a 6 mm diameter and 3 mm height mold in the macro-shear test and 1 mm diameter and 2 mm height mold in the micro-shear test, and then polymerized. The macro- and micro-shear bond strength were measured using a universal testing machine and a micro-shear tester, respectively. The macro- and micro-shear strength were analyzed with ANOVA and a post-hoc Scheffe adjustment ($\alpha$ = .05). The fracture surfaces of the crowns were then examined by scanning electron microscopy to determine the mode of failure. Chi-square test was used to identify the differences in the failure mode. Results. The macro-shear strength and the micro-shear strength differed significantly with the types of substructure (P<.001). Although the ceromer/FRC group showed the highest macroand micro-shear strength, the micro-shear strength was not significantly different from that of the base metal alloy groups. The base metal alloy substructure groups showed the lowest mean macro-shear strength. However, the gold alloy substructure group exhibited the least micro-shear strength. The micro-shear strength was higher than the macro-shear strength excluding the gold alloy substructure group. Adhesive failure was most frequent type of fracture in the ceromer specimens bonded to the gold alloys. Cohesive failure at the ceromer layer was more common in the base metals and FRC substructures. Conclusion. The Vectris substructure had higher shear strength than the other substructures. Although the shear strength of the ceromer bonded to the base metals was lower than that of the gold alloy, the micro-shear strength of the base metals were superior to that of the gold alloy.

• Korean Journal of Materials Research
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• v.31 no.7
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• pp.392-396
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• 2021

Expensive PCBN or ceramic cutting tools are used for processing of difficult-to-cut materials such as Ti and Ni alloy materials. These tools have the problem of breaking easily due to their high hardness but low fracture toughness. To solve these problems, cutting tools that form various coating layers are used in low-cost WC-Co hard material tools, and research on various tool materials is being conducted. In this study, binderless-WC, WC-6 wt%Co, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are densified using horizontal ball milled WC-Co, WC-Co-Mo₂C powders, and spark plasma sintering process (SPS process). Each SPSed Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are almost completely dense, with relative density of up to 99.5 % after the simultaneous application of pressure of 60 MPa and almost no significant change in grain size. The average grain sizes of WC for Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are about 0.37, 0.6, 0.54, and 0.43 ㎛, respectively. Mechanical properties, microstructure, and phase analysis of SPSed Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are investigated.

• Journal of the Korean Society for Heat Treatment
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• v.21 no.6
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• pp.307-313
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• 2008

The tensile deformation and shape recovery behaviors were studied in Ni-Ti shape memory wires showing different transformation characteristics by annealing at $200{\sim}600^{\circ}C$. Both R phase ${\rightarrow}$ B19' martensitic transformation at lower temperature and B2 ${\rightarrow}$ R phase transformation at higher temperature occurred in the shape memory wires annealed at $200{\sim}500^{\circ}C$. Transformation temperature and heat flow of B19' martensite increase but those of R phase main almost constant even with increasing annealing temperature. In the case of wires annealed and then cooled to $20^{\circ}C$, plateau on stress-strain curves in tensile testing can be observed due to the collapse of R phase variants and the formation of deformation-induced B19' martensite. In the case of wires annealed and then cooled to $-196^{\circ}C$, however, plateau on stress-strain curves does not appear and stress increases steadily with increasing tensile deformation. Comparing shape recovery rate with cooling temperature after annealing, shape recovery rate of the wire cooled to $20^{\circ}C$ is higher than that of the wire cooled to $-196^{\circ}C$ after annealing, and maximum shape recovery rate of 95% appears in the wire annealed at $400^{\circ}C$ and then cooled to $20^{\circ}C$. $R_s$ and $R_f$ temperatures measured during shape recovery tests are higher than $A_s$ and $A_f$ temperatures measured by DSC tests even at the same annealing temperature.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.12
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• pp.31-38
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• 1991

The current-voltage characteristics at annealed Be-Cu alloy(1.8-2 wt% Be, 0.2 wt% Co+Ni) interfaces have been studied by means of the cyclic voltammetric method. The specimens were annealed in nitrogen gas($N_{2}$) furnace at 36$0^{\circ}C$ for 1.5 hours. After annealing, the vickers hardness(HV) was increased from 210 to 385. The used solutions were distilled water(H$_{2}$O), 10$^{-3}M\;CsNO_{2},10^{-2}M\;KCl,10^{-2}M\;KOH,10^{-4}M\;H_{2}SO_{4}$ aqueous electrolytes, and ethylalcohol ($C_{2}H_{5}OH$), etc. The cyclic voltammograms showed significant current-voltage characteristics between the annealed and unannealed specimens at the same conditions. The age hardening and the related surface potential barrer and dissolution effects have been observed during the whole experimental process. The dissolution process of annealed Be-Cu alloys was effectively retarded by the age hardening phenomenon. The age hardening effect also raised the surface potential barrier of Be-Cu alloys. The interfacial phenomena of Be-Cu alloys seem to be one of good models for understanding the activation process.

• Journal of Technologic Dentistry
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• v.42 no.2
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• pp.129-137
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• 2020

Purpose: The aim of this study is to observe the compressive fracture strength of the crown according to the direction of the occlusal force of the mandibular canine and carnassial of the small dog. Methods: The abutment models of mandibular canine and carnassial were prepared, specimens of zirconia, PMMA and Ni-Cr alloy were produced. The experimental jig was fabricated with Co-Cr alloy and buried in acrylic resin after make tilt to specified angle. The specimen was attached to a jig and loaded using a universal testing machine until the specimen fractured. Results: The compressive fracture strengths of CXZ and CXP specimens were found to be 999.21 ± 31.15 N on average and 731.42 ± 59.13 N on average. And CZZ and CZP specimens were 730.48 ± 70.14 N on average and 377.65 ± 11.87 N on average. CXN and CZN specimens were not fractured. In addition, MZZ and MZP specimens were 746.46 ± 50.75 N and 258.64 ± 31.86 N on average. The MZN specimens were not fractured. Conclusion: Zirconia has compressive fracture strength that can be applied to small dog's canine and Carnassial prosthetics, while PMMA has inadequate strength to small dog's carnassial prosthesis.

• Journal of Korea Foundry Society
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• v.34 no.2
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• pp.49-53
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• 2014

In commercial Zr-Nb-Cu-Ni-Al amorphous alloys, expensive element, Zr, was substituted to Sn which was cheaper one, and then, glass forming ability, compressive strength and hardness of them were estimated. Even though the Sn was added up to 1.5%, resulting phase was not changed to the crystalline form. It was confirmed by X-ray diffraction and thermal analyses. In the X-ray profiles, there were no peaks for crystalline phases and typical halo pattern for amorphous phase was appeared at the diffraction angle of $35^{\circ}{\sim}45^{\circ}$. Thermal analyses also showed that the Sn modified alloys were corresponded to the amorphous standards where ${\delta}T$(= Tx - Tg) and Trg(= Tg/Tm) affecting to the amorphous forming ability were more than 50K and 0.60 respectively. Compressive strengths were 1.77 GPa, 1.63 GPa, 1.65 GPa and 1.77 GPa for 0%Sn, 0.5%Sn, 1.0%Sn and 1.5%Sn respectively. Hardnesses of the Sn modified alloys were decreased from 752 Hv to 702 Hv in 1.0%Sn and recovered to 746 Hv in 1.5%Sn.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.2
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• pp.182-188
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• 2007

[ $Zr_{50}-Ni_{27}-Nb_{18}-Co_5$ ] amorphous alloys ribbon was prepared by a single-roller melt-spinning technique. In order to improve the hydrogen kinetics Pd-coating were carried out on each side of the amorphous ribbon. Pd prevents oxidation of Zr and catalyses the dissociation of molecular hydrogen to atomic hydrogen. In this work, the hydrogen embrittlement and surface properties on Zr-based amorphous alloys were investigated. The Zr-based amorphous alloys were characterized by X-ray diffractometry(XRD) and differential scanning calorimetry(DSC). The morphology of surface and roughness was observed by using scanning electron microscopy(SEM) and atomic force microscopy (AFM). A lattice parameter of both Pd and Zr-based amorphous alloy was increased after hydrogen permeation at 473 K. After hydrogen permeation at 473 K, some cracks were observed on the surface of Pd, which was the cause for the hydrogen embrittlement. The crystallization temperature of Zr-based amorphous alloy was decreased due to the permeated hydrogen.