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Na2SO4 용융염에서의 Ni 및 N 기 초합금의 부식
김종집,조성문 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.12
The hot salt corrosion of 99.995% pure Ni. IN-100 and IN-713LC alloys by Na₂So₄ melt has been studied at 910℃ in Pt catalyzed 0.2% SO₂-O₂ gas atmosphere. The values of corrosion current density Icorr., measured by the Tafel method increased in IN-100 and IN-713LC alloys after galvanostatic treatment, but decreased in Ni. These effects were interpreted in terms of the change n the basicity of the melt and the protectiveness of the oxide scale during polarization. The values of Icorr. measured after galvanostatic treatment were found to have a correlation with the parameters such as the activation potential and the stabilized potential after the cathodic treatment. However, these parameters and the Icorr. values measured either prior to or after galvanostatic treatment did not correlate well with the long term corrosion resistance of the alloys.
On the Determination of Electrochemical Noise Resistance
김종집 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.2
The effects of sampling duration and sampling frequency on noise resistance were investigated for Type 316 stainless steel in accordance with a standard procedure employed in polarization resistance measurements. Noise resistance was also determined by wavelet transform and compared with that from AC impedance measurements. An optimum sampling duration for noise resistance determination is shown to be 600 s in comparison to the polarization resistance data, and the sampling frequency of 10 Hz is recommended in noise resistance measurements based on the level of instrumental noise and from the comparison with the polarization resistance data. After wavelet transform, the value of noise resistance for smooth coefficients in the lower level of decomposition tends to be independent of the level of decomposition, but the trend is not observed in detail coefficients. Noise resistance is suggested to be determined at a smooth coefficient with the largest level of decomposition in the independent region. The effects of sampling duration and sampling frequency on noise resistance were investigated for Type 316 stainless steel in accordance with a standard procedure employed in polarization resistance measurements. Noise resistance was also determined by wavelet transform and compared with that from AC impedance measurements. An optimum sampling duration for noise resistance determination is shown to be 600 s in comparison to the polarization resistance data, and the sampling frequency of 10 Hz is recommended in noise resistance measurements based on the level of instrumental noise and from the comparison with the polarization resistance data. After wavelet transform, the value of noise resistance for smooth coefficients in the lower level of decomposition tends to be independent of the level of decomposition, but the trend is not observed in detail coefficients. Noise resistance is suggested to be determined at a smooth coefficient with the largest level of decomposition in the independent region.
뜨임처리가 AISI 403 스테인레스강의 Kiscc 에 미치는 영향
김종집,장현구,한범석,문한규 한국부식학회 1989 Corrosion Science and Technology Vol.18 No.1
The plane strain stress corrosion threshold stress intensity factor, K_(ISCC), has been determined for a martensitic stainless steel, AISI 403, in quenched and tempered conditions. The specimens were tempered at three different temperatures of 390℃, 520℃ and 610℃, and tested in 3.5 percent NaCl solution. The measured K_(ISCC) values varied remarkably depending on the tempering temperature: the highest value of 72.3 MPa◎m for 610℃ and the lowest value of 13.3 MPa◎m for 520℃. Fractographic study revealed that the intergranular fracture was dominant after stress corrosion cracking in all the specimens investigated.
흑연 및 공업용 다이아몬드와 동합금의 Wetting 거동 연구
김종집 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.8
The effects of alloying addition on the wetting of graphite and industrial diamond were, studied using sessile drop tests conducted in Ar-atmosphere at 1,100℃. Alloy systems used in this work were Cu-Mn-Sn. Cu-Mn-V and Cu-Mn-Cr. For all of these alloys, wetting of graphite and industrial diamond were found to be improved by increases in the content of carbide formers such as Mn, V and Cr. Among them, Cr was the most effective one. This result was consistent with earlier observations that the wettability of carbon-based materials was strongly dependent upon Gibb’s free energy of formation for carbides involved. The expected increase in activity of the melts, however, was not found in the Cu-Mn-Sn alloys. In the Cu-Mn-V and the Cu-Mn-Cr alloys, the effect of Mn on wettability was different in that Mn was beneficial in the former, while not in the latter alloys.
Electrochemical Noise Analysis of Localized Corrosion by Wavelet Transform
김종집 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.5
Electrochemical noise (EN) was measured during pitting and stress corrosion tests in NaCl solutions for type 403 stainless steel tempered at 390 °C for 2 h. The EN data were analyzed mainly by wavelet transform in terms of the energy contribution of smooth crystal and detail crystals in three frequency regions. In the early stage of the pitting tests, general corrosion occurs, and contribution of smooth crystal to the total energy was greater than that of low frequency detail crystal, but less with the development of meta-stable pitting. A similar trend was observed in the early stage of stress corrosion cracking (SCC) tests. The contribution of low frequency detail crystals to the total energy decreased as stable pits were formed, and it was less than the energy contribution of smooth crystal when crack propagation occurred in the later stage of SCC. In addition, the contribution of energy of high frequency detail crystal is shown to be indicative of the occurrence of plastic deformation. These results demonstrate that the onset of detailed processes in pitting and SCC can be sensitively detected by wavelet analysis in terms of the energy contribution of smooth crystal and low and high frequency detail crystals, but not with that based on the change in position of peak in energy contribution of detail crystals.