• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.203-207
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• 1998

After etching Al-Cu alloy films using $SiCl_4/Cl_2/He/CHF_3$ plasma, a corrosion phenomenon on the metal surface has been studied with XPS (X-ray photoelectron spectroscopy) and SEM (Scanning electron microscopy). In Al-Cu alloy system, the corrosion occurs rapidly on the etched surface by residual chlorine atoms. To prevent the corrosion, the $SF_6$ plasma treatment subsequent to the etch has been carried out. A passivation layer is formed by fluorine-related compounds on etched Al-Cu alloy surface after $SF_6$ treatment, and the layer suppresses effectively the corrosion on the surface as the RF power of $SF_6$ treatment increases. The corrosion could be suppressed successfully with $SF_6$ treatment in the RF power of 150watts.

• Corrosion Science and Technology
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• v.16 no.5
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• pp.257-264
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• 2017

Film of new Ti-15Zr-5Nb alloy formed during galvanic anodizing in orthophosphoric acid solution was characterized by optical microscope, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and Raman micro-spectroscopy. Its anticorrosive properties were determined by electrochemical techniques. The film had a layer with nanotube-like porosity with diameters in 500-1000 nm range. The nano layer contained significant amounts of P and O as well as alloying element. Additionally, Raman micro-spectroscopy identified oxygen as oxygen ion in $TiO_2$ anatase and phosphorous as $P_2O_7{^{4-}}$ ion in phosphotitanate compound. All potentiodynamic polarization curves in artificial Carter-Brugirard saliva with pH values (pH= 3.96, 7.84, and 9.11) depending on the addition of 0.05M NaF revealed nobler behavior of anodized alloy and higher polarization resistance indicating the film is thicker and more compact nanolayer. Lower corrosion rates of the anodized alloy reduced toxicity due to less released ions into saliva. Bigger curvature radii in Nyquist plot and higher phase angle in Bode plot for the anodized alloy ascertain a thicker, more protective, insulating nanolayer existing on the anodized alloy. Additionally, ESI results indicate anodized film consists of an inner, compact, barrier, layer and an outer, less protective, porous layer.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.30-30
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• 2008

In this study, electrochemical impedance characteristics of anodic oxide layer formed on titanium binary alloy surface have been investigated. Titanium oxide layers were grown on Ti-$_XTa$ and Ti-$_XNb$(X=10, 20, 30 and 40 wt%) alloy substrates using phosphoric acid electrolytes.

• Journal of the Korean institute of surface engineering
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• v.35 no.1
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• pp.5-10
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• 2002

This study was performed to investigate the influence of spraying condition to the coating layer properties of Fe-Cr-Ni-Mo-Si-B alloy using the HVOF. The investigations, such as thickness measurement, surface roughness, hardness, friction coefficient, resistance of corrosion were carried out. Matrix is prepared by gritting and coating layer is made of Fe-Cr-Ni-Mo-Si-B alloy powder using HVOF. Alumina gritting layers are superior to steel gritting layers. The less spaying distance, the more coating layer properties confirmed. The optimum spraying condition, in this study, was proved as 13inch spraying distance with feed rate 350rpm (78g/min).

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.4
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• pp.197-210
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• 1999

The hydrogen storage performance and electrochemical properties of $Zr_{1-X}Ti_X(Mn_{0.2}V_{0.2}Ni_{0.6})_{1.8}$(X=0.0, 0.2, 0.4, 0.6) alloys are investigated. The relationship between discharge performance and alloy characteristics such as P-C-T characteristics and crystallographic parameters is also discussed. All of these alloys are found to have mainly a C14-type Laves phase structure by X-ray diffraction analysis. As the mole fraction of Ti in the alloy increases, the reversible hydrogen storage capacity decreases while the equilibrium hydrogen pressure of alloy increases. Furthermore, the discharge capacity shows a maxima behavior and the rate-capability is increased, but the cycling durability is rapidly degraded with increasing Ti content in the alloy. In order to analyze the above phenomena, the phase distribution, surface composition, and dissolution amount of alloy constituting elements are examined by S.E.M., A.E.S. and I.C.P. respectively. The decrease of secondary phase amount with increasing Ti content in the alloy explains that the micro-galvanic corrosion by multiphase formation is little related with the degradation of the alloys. The analysis of surface composition shows that the rapid degradation of Ti-substituted Zr base alloy electrode is due to the growth of oxygen penetration layer. After comparing the radii of atoms and ions in the electrolyte, it is clear that the electrode surface becomes more porous, and that is the source of growth of oxygen penetration layer while accelerating the dissolution of alloy constituting elements with increasing Ti content. Consequently, the rapid degradation (fast growth of the oxygen-penetrated layer) with increasing Ti substitution in Zr-based alloy is ascribed to the formation of porous surface oxide through which the oxygen atom and hydroxyl ion with relatively large radius can easily transport into the electrode surface.

• 연구논문집
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• s.29
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• pp.141-149
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• 1999

Brazing of Fe-Cr-Al alloy was carried out at $1200^{\circ}C$ in vacuum furnace using nickel-based filler metals : BNi-5 powder(Ni-Cr-Si-Fe base alloy} and MBF-50 foil (Ni-Cr-Si-B). The effect of boron content on the stability of oxide scale on the brazed joint was investigated by means of cyclic oxidation test performed at $1050^{\circ}C$ and $1200^{\circ}C$. Apparently, the joints brazed with MBF-50 containing boron showed relatively stable oxidation rates compared to boron-free BNi-5 at both temperatures. However, it was considered that the slower weight loss of MBF-50 brazed specimen wasn’t resulted from the low oxidation rate but from the spallation of oxide layer. The oxide layer consisted of thick spinel oxide on the surface and $Al_2 O_3$ internal oxide layer along the interface between mother alloy and braze, the mother alloy was also eroded seriously by the formation of spinel oxides such as $FeCr_2 O_4$ and $NiCr_2 O_4$ on the surface, likely to be induced by the change of oxide forming mechanism due to diffusion of boron from the braze. On the contrary, the joint brazed with BNi-5 showed the good oxidation resistance during the cyclic oxidation test. It seems that the oxidation can be retarded by the formation of stable $Al_2 O_3$ layer at the surface.

• Journal of Technologic Dentistry
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• v.31 no.4
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• pp.15-23
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• 2009

The aim of this study was to evaluate the bond strength of using a Au bonding agent applied on cp-Ti and nonprecious metal-gold-ceramic system. Metallic frameworks(diameter: 5mm, height: 20mm)(N=56, n=7per group) cast in Ni-Cr alloy, Co-Cr alloy and cp-Ti were obtained using acrylic templates and airborne particle abraded with $110{\mu}m$ aluminum oxide. Au bonding agent was applied on wash opaque firing as intermediate layer. SEM and SEM/EDS line profile were performed on the cutting the cross-section of the metal substrate-porcelain with intermediate Au coating. Groups were tested using shear bond strength(SBS) testing at 0.5mm/min. The mean SBS values for the ceramic-Au layer-metal combination were significantly higher than those ceramic-metal combination. While ceramic-Au layer-cp-Ti combinations failed to increase bond strength instead of using a titanium bonding porcelain. The appication of using Au intermediate layer significantly improve the bond strength combination with metal-ceramic system.

• Corrosion Science and Technology
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• v.11 no.4
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• pp.141-150
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• 2012

Stress corrosion cracks in Alloy 600 compact tension specimens tested at $325^{\circ}C$ in a simulated primary water environment of pressurized water reactor were analyzed by analytical transmission electron microscopy and secondary ion mass spectroscopy (SIMS). From a fine-probe chemical analysis, oxygen was found on the grain boundary just ahead of the crack tip, and chromium oxides were precipitated on the crack tip and the grain boundary attacked by the oxygen diffusion, leaving a Cr/Fe depletion (or Ni enrichment) zone. The oxide layer inside the crack was revealed to consist of a double (inner and outer) layer. Chromium oxides existed in the inner layer, with NiO and (Ni,Cr) spinels in the outer layer. From the nano-SIMS analysis, oxygen was detected at the locations of intergranular chromium carbides ahead of the crack tip, which means that oxygen diffused into the grain boundary and oxidized the surfaces of the chromium carbides. The intergranular chromium carbide blunted the crack tip, thereby suppressing the crack propagation.

• Corrosion Science and Technology
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• v.14 no.3
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• pp.113-119
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• 2015

Alloy 82/182 weld metals had been extensively used in joining the components of the PWR primary system. Unfortunately, there have been a number of incidents of cracking caused by PWSCC in Alloy 82/182 welds during the operation of PWR worldwide. To mitigate PWSCC, optimization of water-chemistry conditions, especially dissolved hydrogen (DH) and Zn contents, is considered as the most promising and effective remedial method. In this study, the PWSCC behaviours of Alloy 182 weld were investigated in simulated PWR environments with various DH content. Both in-situ and ex-situ oxide characterizations as well as PWSCC initiation tests were performed. The results showed that PWSCC crack initiation time was shortest in PWR water (DH: 30cc/kg). Also, high stress reduced crack initiation time. Oxide layer showed multi-layered structures consisted of the outer needle-like Ni-rich oxide layer, Fe-rich crystalline oxide, and inner Cr-rich inner oxide layers, which was not altered by the level of applied stress. To analyse the multi-layer structure of oxides, EIS measurement were fitted into an equivalent circuit model. Further analyses including TEM and EDS are underway to verify appropriateness of the equivalent circuit model.

• Korean Journal of Materials Research
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• v.12 no.5
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• pp.341-346
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• 2002

In order to improve the low wear resistance of Ti-6Al-4V alloy, plasma carburization treatment was newly carried out without consumption of its good specific strength and fatigue life over the temperature. Effect of the plasma carburization was analyzed and compared with the non-treated alloy by microstructural observation, structure characterization and mechanical property test. The plasma treated alloy formed a carburized layer of about 150$\mu\textrm{m}$ in depth from the surface, where a fine and hard particles of TiC and $V_4C_3$ were homogeneously dispersed through the layer. It was also found that an increase of the wear resistance, fatigue life and hardness, due to the hard and fine dispersoids.