• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.72-73
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• 2006

The error function can be calculated based on the Simpson method through a subroutine program. An integration program by FORTRAN language was made for diffusion equations of extended source with infinite extent and limited extent. The results on some alloying elements such as C, Co, Cr, Mn, Mo, Ni and V's diffusion in iron, showed the diffusion distance for Ni and Mo can only be $1{\sim}3\;{\mu}m$ and more distance for Co at common sintering temperature of $1120^{\circ}C$. To refine the particle size of the added elements down to a scale of micrometers is an effective way to get homogeneous distribution.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.4
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• pp.396-405
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• 2002

The purpose of this study was to evaluate the effects of four metal surface treatments on the shear bond strength of reline resin to Ni-Cr alloy. The denture base metal used in this study was Ni-Cr alloy(Ticonium Premium 100. Ticonium Co., U.S.A.). 120 specimens were divided into five metal surface treatments: sandblasting only, MR. BOND(Tokuyama Corp.. Japan), Cesead Opaque Primer(Kuraray Co., Japan), METALPRIMER II(GC Corp., Japan) and Super-Bond C&B(Sun Medical Co., Japan) after sandblasting. They were bonded with one of three reline resins Mild Rebaron(GC Corp., Japan), Mild Rebaron LC(GC Corp., Japan) and Meta Base M(Sun Medical Co., Japan). Then they were thermocycled 1,000 times at temperature of $4^{\circ}C$ and $60^{\circ}C$. The shear bond strengths were measured using the universal testing machine(Instron, Model 4301, England) with a cross-head speed of 2 mm/min. The results were as follows : 1. All metal primers and adhesive cement significantly improved the bond strength of reline resin to Ni-Cr alloy compared with sandblasted specimens. 2. In Mild Rebaron and Mild Rebaron LC. Cesead Opaque Primer showed the highest bond strength, but the differences among Cesead Opaque Primer, MR. BOND and METALPRIMER II were not significant. The bond strength of Cesead Opaque Primer was significantly different with that of Super-Bond C&B. 3. In Meta Base M, Super-Bond C&B showed the highest bond strength, but there was no difference between Super-Bond C&B and three metal primers. 4. There was no difference in the bond strength between Mild Rebaron and Mild Rebaron LC when metal surface was treated with the same method. 5. The bond strengths of Mild Rebaron and Mild Rebaron LC treated with Cesead Opaque Primer were higher than that of Meta Base M. The bond strengths of Mild Rebaron treated with MR. BOND and METALPRIMER II was higher than that of Meta Base M, However, there was no difference among three reline resins treated with Super-Bond C&B.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.2
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• pp.214-225
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• 2000

The purpose of this study was to investigate the effects of investing conditions on the marginal discrepancy of conical telescope outer crown with Co-Cr-Ti alloy(Dentitan) and to compare the marginal discrepancy and the retention force of outer crowns using different pattern materials(plastic foil, casting wax, pattern resin). To evaluate the effects of investing conditions on the marginal discrepancy, patterns with plastic foil were invested under three different liquid/powder ratio conditions using phosphate bonded investment(Univest-nonprecious): standard, 10% decreased and 10% increased. At each liquid/powder ratio condition, metal ring was lined with single or double layers of ceramic ring liner. The marginal discrepancy of outer crown at different investing conditions was measured by ${\times}100$ compact measuring microscope(STM5, Olympus, Japan). For measurement of the marginal discrepancy and the retention force of outer crown using different pattern materials, the investing condition of 10% decreased liquid/powder ratio and double layers of ring liner was selected because this investing condition resulted in the best fit of outer crown. Marginal discrepancy was measured in the same way above and retention force on universal testing machine. Under the conditions of this study, the following conclusions were drawn: 1. The thickness of ring liner had more influence on the marginal discrepancy of outer crown than the liquid/powder ratio, and the acceptable marginal fitness could not be expected at the investing condition directed by investment manufacturer 2. There were no differences in the marginal discrepancy of outer crown among three different pattern materials(P>0.05). 3. Casting wax showed the greatest retention force(1640g) of outer crown, followed by pattern resin(1110g), plastic foil(820g). However, there was no significant difference between plastic foil and pattern resin(P>0.05). 4. Plastic foil showed the least variation in marginal discrepancy and retention force.

• Journal of Powder Materials
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• v.28 no.6
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• pp.478-482
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• 2021

The effect of the process conditions of high-velocity oxygen fuel (HVOF) thermal spray coating on the porosity of the coating layer is investigated. HVOF coating layers are formed by depositing amorphous FeMoCrBC powder. Oxygen pressure varies from 126 to 146 psi and kerosene pressure from 110 to 130 psi. The Microstructural analysis confirms its porosity. Data analysis is performed using experimental data. The oxygen pressure-kerosene pressure ratio is found to be a key contributor to the porosity. An empirical model is proposed using linear regression analysis. The proposed model is then validated using additional test data. We confirm that the oxygen pressure-kerosene pressure ratio exponentially increases porosity. We present a porosity prediction model relationship for the oxygen pressure-kerosene pressure ratio.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.2
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• pp.66-74
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• 2016

In this study, characteristics of TiAl alloy and SCM440 (Cr-Mo steel) have been investigated with the various joining condition by servo motor type friction welder. The experimental factors of friction welder used in this study are spindle revolution, friction speed, and distance, upset speed and distance, respectively. Servo motor type friction welder could be controlled by the level of oil pressure, and it could be performed by position control dependence of electrical energy. Mechanical properties and morphology of welded interface were characterized by various joining condition. This aroused due to the bond strength dependence on friction heat and size of the heat affected zone. Therefore, it is necessary to have enough friction heat and decreased heat affected zone for good friction welding between dissimilar metals. An optimum bond was obtained between TiAl alloy and SCM440 by controlling friction speed and distance. At the spindle revolution 4,000 rpm, friction speed 120 mm/min, friction distance 15 mm, the bond strength was found to be 312 MPa.

• The Journal of the Korean dental association
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• v.53 no.11
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• pp.804-816
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• 2015

PURPOSE: The aim of this study was to evaluate the influence of the oxide layer removal process in the Co-Cr-Mo (CCM) abutment after casting procedure on the prosthesis settlement and screw stability. MATERIALS AND METHODS: CCM abutments of four different interface conditions (CCM-M; machined, CCM-O; oxide layer formed, CCM-B; blasted, CCM-P; polished after blasted) and gold abutment (Gold-C; Cast with type III Gold alloy) were used. The initial settling values of abutments were evaluated according to the difference of implant-abutment length when the tightening torques were applied at 5 Ncm and 30 Ncm, and the settling values of abutments caused by loading were evaluated according to the difference of implant-abutment length before and after loading with 250 N, 100000 cycle. The loss ratios of removal torque for abutment screws were evaluated according to the difference in value of removal torques under 30 Ncm tightening torque applied before and after cyclic loading. RESULTS: The CCM-P and CCM-B group showed a higher initial settling value compared with the Gold-C group (P<.05), while the Gold-C group showed the highest settling values caused by loading (P<.05) and no significant differences were observed for between CCM groups (P>.05). The loss ratio of removal torque values for the CCM-B, CCM-P groups did not differ significantly from that of the Gold-C group (P>.05). CONCLUSION: Even though the oxide layer was removed by different methods, CCM abutment with internal conical connection structure showed lower abutment settling and similar screw loosening after cyclic loading compared with gold abutment.

• Journal of the Korean institute of surface engineering
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• v.31 no.6
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• pp.334-344
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• 1998

Yew coating pmccss t.o form a surface layer ol CrN phasc on mild steel (A81 1020!, AlSI Hi3, 1Cr-0.5Mo steel (ASTM A213 and Nickrl-base superalloy (Inconel 718) was developed. Surlaces of various alloys t,n.ateii by chromizing for the formation ol Cr diffusion layer was subsequently trcaled by plasma nitriding in order t.o form the hard CrS coating layer on the surfaces. This duplex plasma surface tri-atments of chromizing and plasma nitriding have induced a lormation of a duplex-lrcated surfacr hyer of approximat~ls 70-80 $\mu\textrm{m}$thickncss with a iargcly improved microiiardnrss up to approxiniateW 1500Hv(50gf). The main cause for the lage improvment in the surface hardncss is altribilted to [.he fact that CrN and $Fe_xN$ phases are created successfully by ccliromizins and plasma nilriding treatment. High tenipera1,urc wear resislance of the duplex-treated mild steel and HI3 steels at $600^{\circ}C$ was examined. Comparing the duplex-treated specimens with the specimens treated only by chromizing, the rcsults shovmi that, thc wear volume of the duplex-treated mild skcl and 1113 stcel aSt.er a wear test, at $600^{\circ}C$ were reduced hy a Iactor of 8 and 3, respectively. Characteristics of the CrS phase by duplrx treatment were compared with $CrN_x$,/TEX> film by ion plating and the wear behaviors of CrN film lormed by two different nroccsses arc nea.riy identical.

• 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.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.419-428
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• 2020

The kinetics of direct methanation over activated charcoal-supported molybdenum catalyst at 30 bar was studied in a cylindrical fixed-bed reactor. When the temperature was not higher than 400℃, the CO conversion increased with increasing temperature according to the Arrhenius law of reaction kinetics. While XRD and Raman analysis showed that Mo was present as Mo oxides after reduction or methanation, TEM and XPS analysis showed that Mo₂C was formed after methanation depending on the loading of Mo precursor. When the temperature was as high as 500℃, the CO conversion was dependent not only on the Arrhenius law but also on the catalyzed reaction by nanoparticles, which came off from the reactor and thermocouple by metal dusting. These nanoparticles were made of Ni, Fe, Cr and alloy, and attributed to the formation of carbon deposit on the wall of the reactor and on the surface of the thermocouple. The carbon deposit consisted of amorphous and disordered carbon filaments.

• Journal of Korea Foundry Society
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• v.37 no.1
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• pp.21-29
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• 2017

The effects of W content and heat treatment on the microstructure and mechanical properties of Hastelloy C-276 alloy investment castings were discussed. As the W content was increased, dendritic microstructure was refined and network type precipitate formed during solidification was distributed on the dendritic grain boundaries. Cr, Fe and Mn were highly segregated in the Ni-based dendrite matrix, and Mo, W, C and Si were in the precipitates. Due to the heat treatment, fine granular and flake precipitates were newly formed in the matrix, and unresolved network type precipitates remained on the grain boundary. The network type precipitates and the granular and flake precipitates formed by heat treatment were confirmed to be ${\mu}$ phase intermetallic compounds with similar compositions. Due to the increase of the W content and the heat treatment, hardness and tensile strength were significantly increased. However, tensile strength after aging treatment was decreased with the W content. These results can be explained in that brittle fracturing by the unresolved network type precipitates dispersed in the grain boundary was predominant over ductile fracturing by the dimple ruptures originating from the fine granular precipitates in the matrix.