• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.156-168
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• 2023

This study investigates the high temperature oxidation behaviour of a Ni-20Cr-1.2Si (wt.%) alloy in steam from 1200 ℃ to 1350 ℃ by Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD). The results demonstrate that exposed Ni-based alloy developed a thin oxide scale, consisted mainly of Cr₂O₃. The oxidation kinetics obtained from the experimental results was applied to evaluate the hydrogen generation considering a simplified reactor core model with different cladding alloys following an unmitigated Loss-Of-Coolant Accident (LOCA) scenario in a hypothetical Small Modular Reactor (SMR). Overall, experimental data and simulations results show that both Fe-based and Ni-based alloys may enhance cladding survivability, delaying its melting, as well as reducing hydrogen generation under accident conditions compared to Zr-based alloys. However, a substantial neutron absorption occurs when Ni-based alloys are used as cladding for current uranium-dioxide fuel systems, even when compared to Fe-based alloys.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.48-50
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• 2005

Advanced hard materials based on diamond are in common use. In this study our main goal was employed to analyze, the mechanisms for the rich phases and chromium carbide, interface of a diamond grits brazed to a Ni-based brazing filler metal matrix. When Ni-7Cr-3Fe-3B-4Si (wt. %) was utilized as the brazing alloy, an isothermal holding resulted in the various products(Ni-rich/Cr-rich domains, carbide). According to these results, the chemical compounds and chromium carbides products is considered to play an important role in brazing temperature and time. Especially chromium carbide has an influence on brazing junction properties.

• Journal of Powder Materials
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• v.1 no.1
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• pp.66-71
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• 1994

Optical microstructures and mechanical properties of Na gas atomized Al-20Si-5Fe alloying powder and its hot extrudates were studied on 3 different types of powder size distribution. This powder showed the size distribution of 10~210 $\mu\textrm{m}$. Also the microstructures of $\alpha$-Al, primary and eutectic Si and needle shaped intermetallic compounds were observed by optical microscope. These needle shaped intermetallic compounds were identified as ${\delta}Al_4FeSi_2$- by XRD and EDX analysis. The ultimate tensile strength(UTS) of these alloy extrudates was increased from 324 to 390 MPa with decreasing powder size range from 120~210 $\mu\textrm{m}$ to 10~64 $\mu\textrm{m}$. A value of Micro-vic-kers hardness was simillar to the result of UTS. These extrudates showed better wear resistance than those of Al-20Si-2X(X : Ni, Cr, Zr), although they are insensitive to the size distribution. These results indicate that the presentation of ${\delta}Al_4FeSi_2$ intermetallic compounds contributed to the wear resistance improvement.

• Journal of Powder Materials
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• v.18 no.5
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• pp.430-436
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• 2011

Joining of NiO-YSZ to 316 stainless steel was carried out with B-Ni2 brazing alloy (3 wt% Fe, 4.5 wt% Si, 3.2 wt% B, 7 wt% Cr, Ni-balance, m.p. 971-$999^{\circ}C$) to seal the NiO-YSZ anode/316 stainless steel interconnect structure in a SOFC. In the present research, interfacial (chemical) reactions during brazing at the NiO-YSZ/316 stainless steel interconnect were enhanced by the two processing methods, a) addition of an electroless nickel plate to NiO-YSZ as a coating or b) deposition of titanium layer onto NiO-YSZ by magnetron plasma sputtering method, with process variables and procedures optimized during the pre-processing. Brazing was performed in a cold-wall vacuum furnace at $1080^{\circ}C$. Post-brazing interfacial morphologies between NiO-YSZ and 316 stainless steel were examined by SEM and EDS methods. The results indicate that B-Ni2 brazing filler alloy was fused fully during brazing and continuous interfacial layer formation depended on the method of pre-coating NiO-YSZ. The inter-diffusion of elements was promoted by titanium-deposition: the diffusion reaction thickness of the interfacial area was reduced to less than 5 ${\mu}m$ compared to 100 ${\mu}m$ for electroless nickel-deposited NiO-YSZ cermet.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.5
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• pp.538-544
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• 2013

In this study, cavitation characteristics of a thermal spray coating were evaluated in order to improve durability and cavitation resistance. For a coating material, a Ni-based self-fluxing alloy was thermal-sprayed over a ALBC3 alloy substrate and subsequently modified by heat treatment.The resulted self-fluxing coating layer had relatively high hardness compared to the base material, and thus would be expected to exhibit good durability. However, the cavitation characteristics were deteriorated due to the intrinsic porous structure of the coating. Therefore, it is essential to optimize heat treatment condition during thermal spraying coating process for self-fluxing alloy, and in this research the increase in heat treatment temperature is thought to increase the fluidity of B and Si in the self-fluxing alloy and to remove pores or defects, leading to the characteristics enhancement.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.1
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• pp.57-62
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• 2008

From the progressing results, it was found that thin film using 52 wt% Ni - 38 wt% Cr - 3 wt% Al - 4 wt% Mn - 3 wt% Si target has good characteristics for low TCR (temperature coefficients of resistance) and high resistivity. The optimum sputtering condition was DC 250 W, 5 mtorr, and 50 sccm and the proper annealing condition was $350^{\circ}C$/3.5 hr in air atmosphere. At these fabricated conditions, thin film resistors with TCR values of less than ${\pm}10ppm/^{\circ}C$ were obtained. The TCR of the packaged-samples made at proper fabrication conditions was $-3{\sim}15ppm/^{\circ}C$ after the thermal cycling and $-20{\sim}180ppm/^{\circ}C$ after PCT (pressure cooker test), we could confirm reliability for the thin film resistor and find the need for enduring research about packaging method.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.835-842
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• 1999

Si3N4 -Si3N4 joints were made using Ag-Cu-Ti and Ag-Cu-In-Ti via brazing method and the change in joint strength was investigated after heat treatment at $400^{\circ}C$ or $650^{\circ}C$ for up to 2000h. The initial strength of as-brazed joints with Ag-Cu-In-Ti was lower but the reduction of the strength was less dramatic than that with Ag-Cu-Ti. The joints made of a new brazing alloy Au-Ni-Cr-Mo-Fe which is developed for high temperature applications were heat-treated at $650^{\circ}C$ for 1000h. As the heat treatment time increased the bond strength increased. The results of the joining system with Mo or Cu interlayer showed that the strength of the joint with Mo interlayer was higher but the system incurred problems in joint production Also it was found from oxidation experiment that Ti and In affected the oxidation resistance of brazing alloy.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.211-218
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• 2014

In this paper the magnetic field properties of the soft magnetic alloys (Fe-Si-Cr and Fe-Ni-Cr) are studied in advance for the development of electro-magnetic shielding films, which could be used in the IT Devices (NFC, mobile phone, computer, etc.).As a result each of the selected soft magnetic alloy melts of the corresponding compositions is water-dispersed into the disk-shaped grains, which are soaked in polymer resin, and of which two types of thin film of thickness 0.1mm and 1mm are made by passing through the heating calendar roller. And the magnetic permeability and the shielding effectiveness of the polymer films containing the soft magnetic alloy grains are measured over the whole frequency bands from the low frequency to 10GHz. Before the experiments of the soft magnetic alloy, a special equation is proposed to estimate the permeability of the alloy, and the equation is verified with the pre-published data by MATLAB, and from which the most optimal compositions can be decided. And the SE(Shielding Effectiveness) of the polymer films containing the soft magnetic alloy grains is simulated by the HFSS.

• Journal of Powder Materials
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• v.2 no.1
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• pp.53-62
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• 1995

TLP(Transient-Liquid-Phase) bonding of Fe-base MA956 ODS alloy was performed. As insert metal a commercially available Ni-base alloy(MBF50) and an MA956 alloy with additive elements of 7wt% Si and 1wt% B were used. To confirm the idea that a concurrent use of MA956 powder with Insert metals can enhance the homogenization of constituent elements and thereby reduce the thickness of joint interface, MA956 powder was also inserted In a form of sheet. SEM observation and EDS analysis revealed that Cr-rich phase was formed in the bonded interface in initial stage of isothermal solidification during the bonding process, irrespective of kind of insert metals. Measurement of hardeness in the region of bonded interface and EDS analysis showed that a complete homogenization of composition could not be obtained especially in case of MBF50. Joints using either BSi insert metals only or BSi insert together with MA956 powder interlayer showed, however, a remarkable improvement in a compositional homogenization, even though a rapid grain growth in the bonded interface could not be hindered.

• Journal of Welding and Joining
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• v.18 no.3
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• pp.51-59
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• 2000

Sink roll has been used in molten 55%Al-Zn alloy bath of continuous galvanizing line for sinking and stabilizing working steel strip in molten metal bath. In the process, the sink roll body inevitably build up dross compounds and pitting on the sink roll surface during 55%Al-Zn alloy coated strip production, and the life time of the sink roll is shorten by build up dross compounds and pitting. The present study examined the application of thermally sprayed ceramic coatings method on sink roll body for improving erosion resistance at molten 55% Al-Zn pool. In this experiment, the stainless steels such as STS 316L and STS 430F were used as the substrate materials. The CoNiCr and WE-Co powder were selected as bond coating materials. Moreover $Al_2O_3-ZrO_2-SiO_2 and ZrO_2-SiO_2$ powders selected as the top coating materials. Appearances of the specimens before and after dipping to molten 55%Al-Zn pool were compared and analyzed. As a result of this study, STS430F of substrate, WC-Co of bond spray coatings, $ZrO_2-SiO_2$ power of top spray coatings is the best quality in erosion resistance test at molten 55%Al-Zn pool