한국부식방식학회

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치과용 Ni-Ti합금의 표면특성에 미치는 Mo함량의 영향
Ni-Ti shape memory alloy for dental nerve treatment devices was prepared by adding Mo to Ni-Ti alloy to improve flexibility and fatigue fracture characteristics and simultaneously increase corrosion resistance. Surface properties of the alloy were evaluated. Microstructure analysis of the Ni-Ti-xMo alloy revealed that the amount of needle-like structure increased with increasing Mo content. The shape of the precipitate showed a pattern in which a long needle-like structure gradually disappeared and changed into a small spherical shape. As a result of XRD analysis of the Ni-Ti-xMo alloy, R-phase structure appeared as Mo was added. R-phase and B2 structure were mainly observed. As a result of DSC analysis, phase transformation of the Ti-Ni-Mo alloy showed a twostep phase change of B2-R-B19\' transformation with two exothermic peaks and one endothermic peak. As Mo content increased, R-phase formation temperature gradually decreased. As a result of measuring surface hardness of the Ti-Ni-Mo alloy, change in hardness value due to the phase change tended to decrease with increasing Mo content. As a result of the corrosion test, the corrosion potential and pitting potential increased while the current density tended to decrease with increasing Mo content.
KEYWORDs : Ni-Ti file, Shape memory alloy, R-phase, Corrosion resistance, Ni-Ti-Mo alloy
AUTHORs : 최한철†·김재운·박순균

Page : 55 - 63 DOWNLOAD
불특정 공식손상을 가진 316L 스테인리스강의 기계적 물성치 예측을 위한 다중선형회귀 적용
The aim of this study was to propose a multiple linear regression (MLR) equation to predict ultimate tensile strength (UTS) of 316L stainless steel with unspecified pit corrosion. Tensile specimens with pit corrosion were prepared using a potentiostatic acceleration test method. Pit corrosion was characterized by measuring ten factors using a confocal laser microscope. Data were collected from 22 tensile tests. At 85% confidence level, total pit volume, maximum pit depth, mean ratio of surface area, and mean area were significant factors showing linear relationships with UTS. The MLR equation using these three significant factors at a 85% confidence level showed considerable prediction performance for UTS. Determination coefficient (R2`) was 0.903 with training and test data sets. The yield strength ratio of 316L stainless steel was found to be around 0.85. All specimens with a pit corrosion presented a yield ratio of approximately 0.85 with R2 of 0.998. Therefore, pit corrosion did not affect the yield ratio.
KEYWORDs : Multiple linear regression, 316L stainless steel, Unspecified pit, Mechanical properites
AUTHORs : 정광후·김성종†

Page : 44 - 54 DOWNLOAD
고온 고압 응력부식균열 개시 시험용 디스크 시편의 응력과 변형에 대한 유한요소 해석
The rupture disk corrosion test (RDCT) method was recently developed to evaluate stress corrosion cracking (SCC) and was found to have great potential for the real-time detection of SCC initiation in a high temperature and pressure environment, simulating the primary water coolant of pressurized water reactors. However, it is difficult to directly measure the stress applied to a disk specimen, which is an essential factor in SCC initiation. In this work, finite element analysis (FEA) was performed using ABAQUSTM to calculate the stress and deformation of a disk specimen. To determine the best mesh design for a thin disk specimen, hexahedron, hex-dominated, and tetrahedron models were used in FEA. All models revealed similar dome-shaped deformation behavior of the disk specimen. However, there was a considerable difference in stress distribution in the disk specimens. In the hex-dominated model, the applied stress was calculated to be the maximum at the dome center, whereas the stress was calculated to be the maximum at the dome edge in the hexahedron and tetrahedron models. From a comparison of the FEA results with deformation behavior and SCC location on the disk specimen after RDCT, the most proper FE model was found to be the tetrahedron model.
KEYWORDs : Alloy 600, Finite element analysis, Primary water stress corrosion cracking, Rupture disk corrosion test, SCC initiation
AUTHORs : 김태영·김성우†·김동진·김상태

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Exploring the Properties and Potential of Single-crystal NCM 811 for Lithium-ion Batteries
Single-crystal Ni-rich NCM is a material that has drawn attention in the field of lithium-ion batteries due to its high energy density and long cycle life. In this study, we investigated the properties of single-crystal NCM 811 and its potential for use in lithium-ion batteries. High-quality single crystals of NCM 811 were successfully synthesized by crystal growth via a flux method. The single-crystal nature of the samples was confirmed through detailed characterization techniques, such as scanning electron microscopy and x-ray diffraction with Rietveld refinement. The crystal structure and electrochemical performances of the single-crystal NCM 811 were analyzed and compared to its poly-crystal counterpart. The results indicated that single-crystal NCM 811 had electrochemical performance and thermal stability superior to poly-crystalline NCM 811, making it a suitable candidate for high-performance batteries. The findings of this study contribute to a better understanding of the characteristics and potential of single-crystal NCM 811 for lithium-ion batteries.
KEYWORDs : NCM 811, Flux Method, Single-Crystal NCM, Li-Ion Batteries
AUTHORs : Yongseok Lee and Seunghoon Nam†

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Mechanical and Structural Behaviors of HfN Thin Films Fabricated by Direct Current and Mid-frequency Magnetron Sputtering
Hafnium nitride (HfN) thin films were fabricated by mid-frequency magnetron sputtering (mfMS) and direct current magnetron sputtering (dcMS) and their mechanical and structural properties were compared. In particular, changes in the HfN film properties were observed by changing the pulse frequency of mfMS between 5 kHz, 15 kHz, and 30 kHz. The crystalline structure, microstructure, 3D morphology, and mechanical properties of the HfN films were compared by x-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, and nanoindentation tester, respectively. HfN film deposited by mfMS showed a smoother and denser microstructure as the frequency increased, whereas the film deposited by dcMS showed a rough and sloppy microstructure. A single δ-HfN phase was observed in the HfN film made by mfMS with a pulse frequency of 30 kHz, but mixed δ-HfN and HfN0·4 phases were observed in the HfN film made by dcMS. The mechanical properties of HfN film made by mfMS were improved compared to film made by dcMS.
KEYWORDs : Pulse frequency, Direct current, Thin film, Magnetron sputtering, HfN
AUTHORs : Sung-Yong Chun†

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Corrosion Behavior Optimization by Nanocoating Layer for Low Carbon Steel in Acid and Salt Media
In this paper, a SiC nano electroless nickel plating layer with excellent corrosion resistance was fabricated using the Taguchi method. The electroless plated low carbon steel was subjected to tests to examine the influence of corrosive media, microhardness, and corrosion rate on the corrosion resistance of this alloy. Three different corrosive media (HCl, Na2SO4, and NaCl) at various temperatures (80, 90, and 100 oC) were used, and at three different times (40, 80, and 120 min.) with a speed of stirring equal to 500 rpm. The results of microhardness were found from 134.276 HV to 278.578 HV at various conditions, while the corrosion rate results were obtained from 0.89643 mpy to 7.12571 mpy at different circumstances. Corrosion, and mechanical characteristics were explained using Taguchi design. Taguchi technique was used to account for all possible combinations of elements in order to conduct a complete study. Models that link the response and procedure parameters were developed using the results of these tests, and the analysis of variance was utilized to validate these models (ANOVA). For maximum efficiency, a function called “desirability” was applied to all responses at once.
KEYWORDs : Electroless plating, Corrosion resistance, Nanocomposites coatings, Taguchi method
AUTHORs : Ahmed S. Abbas, Bahaa Sami Mahdi, Haider H. Abbas, F.F. Sayyid†, A.M. Mustafa, Iman Adnan Annon, Yasir Muhi Abdulsahib, A.M. Resen, M. M. Hanoon, and Nareen Hafidh Obaeed

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Corrosion Inhibition Screening of 2-((6-aminopyridin-2-yl)imino)indolin-3-one: Weight Loss, Morphology, and DFT Investigations
Because of its inexpensive cost, mild steel is frequently employed as a construction material in different industries. Unfortunately, because of its limited resistance to corrosion, a protective layer must be applied to keep it from decaying in acidic or basic environments. The presence of heteroatoms, such as nitrogen, oxygen, and pi-electrons in the Schiff base could cause effective adsorption on the mild steel surface, preventing corrosion. The weight loss method and scanning electron microscopy (SEM) were used to investigate the inhibitory effects of APIDO on mild steel in a 1 M hydrochloric acid environment. The efficiency of inhibition increased as the inhibitor concentration increased and decreased as the temperature increased. The SEM analysis confirmed that the corrosion inhibition of APIDO proceeded by the formation of an organic protective layer over the mild steel surface by the adsorption process. Simulations based on the density functional theory are used to associate inhibitory efficacy with basic molecular characteristics. The findings acquired were compatible with the experimental information provided in the research.
KEYWORDs : Isatin, Schiff base, Mild steel, Corrosion inhibitor, DFT
AUTHORs : Nadia Betti and Ahmed A. Al-Amiery†

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Inhibitory Effect of Benzoate-intercalated Hydrotalcite with Ce3+-loaded clay on Carbon Steel
This work studied the inhibitory effect of the combination of benzoate-intercalated hydrotalcite (HT-BZ) and Ce3+-loaded clay (Clay-Ce) on carbon steel (CS). HT-BZ was prepared by the co-precipitation method and Clay-Ce was fabricated by a cation exchange reaction. HT-BZ and Clay-Ce were assessed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) coupled with zeta potential measurement. Electrochemical measurements coupled with scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) were used for studying the inhibitory action of the mixture of HT-BZ and Clay-Ce on steel electrodes immersed in 0.1 M NaCl. For comparison, the inhibitory effect of HT-BZ or Clay-Ce alone was also evaluated. The results showed that HT-BZ combined with Clay-Ce provided synergistic inhibition of the CS substrate. The mixture of 0.5 g/L HT-BZ + 0.5 g/L Clay-Ce provided 93.5% inhibition efficiency. The protective mechanism of the HT-BZ + Clay-Ce mixture consisted of the reaction of released BZ and Ce3+ and the deposition of HT-BZ and Clay-Ce structures on the CS substrate.
KEYWORDs : Corrosion inhibition, Carbon steel, Hydrotalcite, Benzoate, Ce3+-loaded clay
AUTHORs : Thuy Duong Nguyen†, Thu Thuy Pham, Anh Son Nguyen, Ke Oanh Vu, Gia Vu Pham, and To Thi Xuan Hang†

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