오오스테나이트 스테인레스강에서 Si 첨가가 응력부식파괴에 미치는 영향

변수일,한유동 대한금속재료학회(대한금속학회) 1981 대한금속·재료학회지 Vol.19 No.6

The effect of Si addition on the stress corrosion cracking (SCC) of austenitic stainless steel was studied in the boiling aqueous solution of 42% MgCl₂. Failutre time, under constant load, remained nearly constant for the specimen with Si content up to 1.42 wt.%, however, it increased drastically as Si content increased from 1.42 to 2.21 wt.%, and further increase in Si content did not affect the failure time. Metallographic examination showed that the specimen with Si <1.42 wt.% and Si> 2.21 wt.% had austenitic single phase and austenitic-ferritic duplex phase respectively. The increased failure time caused by Si addition was explained in terms of retardation of SCC growth due to ferrite phase and formation of stable passive film. No change in pitting potential(breakdown) was observed for both unstressed and stressed specimen regardless of its Si content respectively. The stressed specimen showed lower (more anodic) pitting potential than the unstressed. Critical passivation current density (critical anodic partial current density), in pass estimated from electrochemical polarization curve and weight loss measurement decreased with Si addition and higher passivation current density was observed with the stressed specimen compared with the unstressed.

Current Transient Technique 의 원리 및 계면전기화학에의 응용

변수일,한정남,신헌철 한국부식학회 1998 Corrosion Science and Technology Vol.27 No.2

This paper explained the principles of the current transient technique and their applications to such practical electrochemical systems as hydrogen and lithium intercalation systems. The atom and/or canon transport through Pd, transition metal oxide and hydride forming electrode has been well described on the basis of the analysis of the current transient. The current transient characterised by the transport obeying Fick's law shows first a linear relationship between flux and time in logarithmic scale with a slope of -1 / 2 and then a steep exponential decay with time, which is termed the two-staged behaviour. However, in the presence of trapping, stress-induced diffusion, phase boundary movement and electric field, the current transient is specified by non-Fickian behaviour which deviates from the two-staged behaviour. Based upon the analysis of the current transient, we investigated the influence of each factor on the hydrogen/lithium transport through the electrode.

순철의 입계부식에 대한 속도론적 고찰

변수일,최재훈 대한금속재료학회(대한금속학회) 1984 대한금속·재료학회지 Vol.22 No.5

The corrosion experiments of iron were performed in boiling 55% Ca(NO₃)₂solution (115℃) to elucidate kinetics of intergranular corrosion (IGC) of iron. Four kinds of iron specimens were used in this study. Three kinds of specimens with the following different chemical compositions were prepared from a starting material with 20 to 40 ppm C, 17 ppm N, and 20 ppm P. One batch (A) of this material was normalized only, a second batch (B) was also decarburized up to under 10 ppm C prior to normalizing, and a third batch (C) was decarburizbd, and then nitrided up to 140 to 220 ppm N prior to normalizing. The fourth specimen (O) contained 200 ppm C, 60 ppm N, and 110 ppm P (Armco iron). All normalized specimens (A, B, C, O) were annealed (A₁,B₁,C₁,O₁) and tempered (A₂,B₂,C₂,O₂). After the specimen was exposed for 15 min to 24 h to the IG Ctest solution at 1000 mV_SHE (passive region) and the time-current curve was recorded, the specimen was then examined for IGC by optical microscopy. The time-current curves and optical micrographic observations suggested that IGC occurred after passivation of specimen and passivation is also necessary for occurrence of IGC of iron. All normalized (A, B, C, O), the annealed (A₁,B₁,C₁,O₁) and the tempered (A₂,B₂,C₂) specimens show no intergranular attack. Only the annealed (O₁) and tempered (O₂) Armco iron specimens were markedly susceptible to IGC. The excess dissolved nitrogen or nitride at the grain boundaries (gbs) does not lead to a definite IGC. The presence of fine carbides at the gbs may cause IGC, but a critical amount of carbon at the gbs may be necessary for occurrence of IGC.

Al-Zn-Mg 합금의 전노출취성과 응력부식파괴 사이의 관계에 대한 연구

변수일,김홍표,이성민 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.11

The stress-corrosion cracking (SCC) mechanism of Al-Zn-Mg alloy has been studied in terms of the relationship between pre-exposure embrittlement (PEE) and SCC. PEE and SCC susceptibilities were measured as a function of ageing state, pre-exposure time and applied potential by means of the slow strain rate method. The specimen pre-exposed to water vapour-saturated air, followed by reheat treatment (re-solutionized in vacuum and aged in dry air) showed a pronounced increase in fracture energy as compared to the pre-exposed specimen. This suggests that PEE is caused by reversible embrittlement, i.e., by hydrogen embrittlement. The similar trends in SCC susceptibility were obtained with respect to ageing state as well as to applied potential. This implies that the SCC mechanism remains unchanged regardless of ageing state and applied potential. When pre-exposure time was large enough than 120 h, the susceptibility to PEE and fracture surface of PEE were very similar to those associated with SCC. On the basis of experimental results, it is believed that SCC as well as PEE is caused by hydrogen embrittlement

액상금속 취성의 기구와 원인

변수일 한국부식학회 1983 Corrosion Science and Technology Vol.12 No.3

일정변형율속도법에 의한 고순도 Al-Zn-Mg 합금의 응력부식파괴에 대한 속도론적 고찰

변수일,김홍균 대한금속재료학회(대한금속학회) 1984 대한금속·재료학회지 Vol.22 No.7

The kinetics of stress-corrosion cracking (SCC) of a high purity Al-Zn-Mg alloy was studied as a function of applied potential, temperature and kind of corrosive media. The SCC tests were carried out in the range of applied potential from -550 to -2150 mV_(SHE) and at the temperatures between 288 and 318 K. 3.5 wt.% NaCl solution (PH=1), air and transformer oil were used as corrosive medium. The percentage elongation and the fracture energy due to SCC increased with decreasing applied potential from -550 to -1150 mV_(SHE) and then decreased. The SCC fractography correspondingly revealed a decreased intergranular-brittle fracture fraction with decreasing applied potential up to -1150 mV_(SHE) and then increased one with decreasing applied potential up to -2150 mV_(SHE). Average SC crack propagation rate, γ, was calculated by introducing a new function related to the σ-εcurve in the inert environment. It was also observed to be 100×10^(-6), 39×10^(-6) and 2.1×10^(-4) ㎜ sec^(-1) at the applied potential of -550, -750 and -1150 mV_(SHE), respectively, tested under the strain rate 8.3×10^(-7) sec^(-1) with the underaged specimen. The observed values are in good accord with the calculated values. The intergranular-brittle fracture mode was also observed in oil, probably caused by the water in oil. Stress-corrosion (SC) fracture mode varied from a simply corroded fracture near the surface/subsurface, followed by an intergranular-brittle fracture over the mixed fracture, composed of the intergranular-brittle fracture and a dimpled rupture, to the pure dimpled rupture in the interior of specimen. It is suggested, on the basis of the observation of potential dependence of the fracture energy and SCC fractography, that SCC is caused by hydrogen-assisted embrittlement. Activation energy for hydrogen-assisted embrittlement in the NaCl solution was found to be 18-20 kJ mole^(-1) for the specimen aged at 180℃ for 0.5h (underaged stage).

인터칼레이션 화합물의 열역학 및 속도론적 개요

변수일,배준성 한국부식학회 1994 Corrosion Science and Technology Vol.23 No.1

부식성 분위기에서의 재료 선정

변수일 한국부식방식학회(구 한국부식학회) 1983 부식 및 방식 강습회 Vol.- No.-

Synthesis and Characterisation of Mixed Conducting Perovskite Type Oxide and Its Electrochemical Application to Electrode Material for Solid Oxide Fuel Cell

변수일,김유미,이경자,김주식 한국전기화학회 2007 한국전기화학회지 Vol.10 No.2

This article is concerned with synthesis, characteriducting perovskite type oxide to electrode materials for solid oxide fuel cell. First, this review provides a compre-hensive survey of the various synthetic methods such as solid state reaction, Pechini, glycine nitrate process and sol-gel methods for the preparation of perovskite type oxide powders. Subsequently, the electrical and microstructuralproperties of the mixed conducting oxides were discussed in detail. Finally, as electrochemical applications of themixed conducting perovskite type oxides to electrode materials for solid oxide fuel cell, fundamentals of theoreticalac-impedance model for porous mixed conducting electrodes iour of porous and dense mixed conducting electrodes prepared by various synthetic methods was discussed.

전자착색 재료 ( Electrochromic Materials ) 란 무엇인가 ?

변수일,김창하 한국부식학회 1991 Corrosion Science and Technology Vol.20 No.2