인코넬 합금의 열처리에 따른 입계 탄화물 석출 및 입계응력부식 거동

맹완영,남태운 ( Wan Young Maeng,Tae Woon Nam ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.4

Inconel alloys used as nuclear power plant components have experienced intergranular stress corrosion cracking problems inspite of their good corrosion characteristics. In order to investigate the effects of heat treatments on carbide precipitation and intergranular stress corrosion cracking(IGSCC) in Inconel alloys, DSC(Differential Scanning Calorimeter), TEM, EDXS and static potential corrosion tests were carried out. Thermal treatment at 750℃ for 15hours in Inconel alloys increased the density of intergranular carbide. The carbides are mainly Cr_7C₃ in Inconel 600, and Cr_(23)C_6 in Inconel 690. The Cr depletion around grain boundary is not crucial factor on IGSCC. The carbides in grain boundary play an important role as acting dislocation source, and as decreasing stress around growing crack.

가스분무법에 의해 급냉응고된 Al-Fe 합금분말의 응고조직

맹완영,남태운 ( Wan Young Maeng,Tae Woon Nam ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.2

N/A The Al-Fe alloy powders were rapidly solidified by gas atomization. Rapidly solidified Al-Fe alloy powders for ranges of composition from 0 to 8wt.%Fe have various microstructure, i.e., cellular, dendritic or two-zone structure. Some small particles(∼10㎛ or less) of Al-Fe alloy at concentrations between 0 and 8wt.%Fe are undercooled significantly prior to solidification and exhibit a two-zone structure in individual powder particles. X-ray diffraction patterns were obtained with Copper K(λ=1.5418Å) in diffractometer to study the extension of the solubility limit of Fe in Al. Lattice parameters were estimated from extrapolation by means of the Nelson-Riley function. The X-ray diffraction patterns for the alloy powders containing up to 4wt.%Fe do not show intensity peak of FeAl₃phase. And the diffraction angles for α Al are shifted up to 4wt.%Fe alloy powders. Thus 4wt.%Fe probably represents the limit of metastable solubility of Fe in Al solidified by gas atomization.

316LN 스테인레스강의 고온 피로균열진전특성

맹완영,강영환,남태운 ( Wan Young Maeng,Young Hwan Kang,Tae Woon Nam ) 대한금속재료학회 ( 구 대한금속학회 ) 1997 재료강도 심포지엄 Vol.- No.-

유무기 TiO₂-SiO₂ 혼성코팅에 미치는 전구체 배합비율의 영향

김동규,맹완영,Kim, Dong Kyu,Maeng, Wan Young 한국재료학회 2016 한국재료학회지 Vol.26 No.5

When a single inorganic precursor is used for the synthesis of a sol-gel coating, there is a problem of cracking on the surface of coating layer. In order to solve this problem of surface cracking, we synthesized inorganic-organic coatings that have hybrid properties of inorganic and organic materials. Sols of various ratios (1:0.07, 0.2, 0.41, 0.82, 1.64, 3.26, 6.54, 13.2) of an inorganic precursor of Tetrabutylorthotitanate ($Ti(OBu)_4$, TBOT) and an organic precursor of ${\gamma}$-Methacryloxy propyltrimethoxysilane (MAPTS) were prepared and coated on stainless steels (SUS316L) by dip coating method. The binding structure and the physical properties of the synthesized coatings were analyzed by FT-IR, FE-SEM, FIB (Focused Ion Beam), and a nano-indenter. Dynamic polarization testing and EIS (electrical impedance spectroscopy) were carried out to evaluate the micro-defects and the corrosion properties of the coatings. The prepared coatings show hybrid properties of inorganic oxides and organic materials. Crack free coatings were prepared when the MAPTS ratio was above a critical value. As the MAPTS ratio increased, the thickness and the corrosion resistance increased, and the hardness decreased.

고분자 분산제 주입을 통한 철산화물(Magnetite, Fe3O4) 입자의 분산 안정성 향상

송근동 ( Geun Dong Song ),김문환 ( Mun Hwan Kim ),이용택 ( Yong Taek Lee ),맹완영 ( Wan Young Maeng ) 한국공업화학회 2013 공업화학 Vol.24 No.6

The iron oxide (Fe3O4) particles in the coolant of the secondary system of a nuclear power plant reduce the heat transfer performance or induce corrosion on the surface of the heat transfer tube. To prevent these problems, we conducted a study to improve the dispersion stability of iron oxide using polymeric dispersant injection in simulated secondary system water. The three kinds of anionic polymers containing carboxyl groups were selected. The dispersion characteristics of the iron oxide particles with the polymeric dispersants were evaluated by performing a settling test and measuring the transmission, the zeta potential, and the hydrodynamic particle size of the colloid solutions. Polymeric dispersants had a significant impact on the iron oxide dispersion stability in an aqueous solution. While the dispersant injection tended to improve the dispersion stability, the dispersion stability of iron oxide did not increase linearly with an increase in the dispersant concentration. This non-linearity is due to the agglomerations between the iron oxide particles above a critical dispersant concentration. The effect of the dispersant on the dispersion stability improvement was significant when the dispersant concentration ratio (ppm, dispersant/ magnetite) was in the range of 0.1 to 0.01. This suggests that the optimization of dispersant concentration is required to maximize the iron oxide removal effect with the dispersant injection considering the applied environments, the iron oxide concentration and the concentration ratio of dispersant to iron oxide.

Inconel 600, 900 및 Incoloy 800 의 산화거동 비교

맹완영,강영환,주기남,유우석 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.12

Spalled oxide particles and corrosion products released from the surface of steam generator materials cause various problems of accelerating stress corrosion cracking, denting, wastage, erosion of turbine, and decrease of thermal efficiency. Because the major part of exposed material surface in steam generator atmosphere is the surface of the steam generator tube, it is important to know the oxidation behavior of the tube material. The oxidation behavior of three kinds of Inconel alloys, i.e., Inconel 600, Inconel 690 and Incoloy 800 in air, pure water, and steam was studied and the oxide layers were analysed by SEM, EDX, X-ray diffractometer. And thermal diffusivities of Inconel alloys were measured by the laser flash method. Inconel 690 shows the best resistance to oxidation among the three alloys tested in static air, pure water, and steam. The good oxidation resistance of Inconel 690 is due to maintaining uniform Cr₂O₃ layer during the oxidation time. The thermal diffusivity decreases as the extent of oxidation increases. The thermal diffusivity of Inconel 600 oxidized at 500℃ for 3hours in static air decreases to 85% of that of non-oxidized specimen. The results of this study can be applied to the development of oxidation resistant materials of controlled Cr content. And the test data can be used as reference for the estimation of the amount of sludge, and as input data of steam generator design.

분말 제조변수의 조절에 의한 가스 분무 조업의 최적화

맹완영,강영환 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.6

The optimized condition for preventing metal delivery tube from freezing up during atomization was evaluated by analyzing the experimental data of gas atomizations which were carried out on various conditions. The optimum condition was established by controlling the protrusion length and the temperature of metal delivery tube. It was observed that powder shape is affected by the collision of particles. The probability of collision among particles can be controlled by changing atomization variables such as protrusion length of metal delivery tube, nozzle slit size and the condition of atomizing chamber. So it is possible to control the powder shape by changing the atomizing variables. It was also shown that the average particle size decrease with increasing atomizing pressure.

고온 고압 수 환경에서 인코넬 600 의 부식 피로 균열 성장 거동

남태운,맹완영,강영환,Ohashi, S .,Ishihara, T . 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.10

It is important to predict the corrosion fatigue crack growth rate of Inconel 600 for the structural integrity of nuclear power plants. In order to evaluate the corrosion fatigue crack growth rate of Inconel 600 in various applied load types, 3 different types of cracking loads which simulate corrosion fatigue, SCC and mixed mechanism of corrosion fatigue and SCC were applied to CT type Inconel 600 specimens in high temperature water at 290℃ with 4ppm dissolved oxygen concentration. There was synergistic effect on corrosion fatigue crack growth rate when mixed mode of SCC and corrosion fatigue load is applied to Inconel 600 specimens in the environment. The measured crack growth rate of the specimen to which mixed load were applied wsa faster than the predicted crack growth rate based on the superposition model. The increase in the crack growth rate indicates that there is sysnersistic interaction of fracture process at the growing crack tip which experiences mixed load of SCC and corrosion fatigue. So it is necessary to account for the synergistic acceleration of corrosion fatigue crack growth to predict the life of structural components of Inconel 600 alloys in corrosive environments.

고온 . 고압 환경하에서 정전위법에 의한 인코넬합금의 입계응력부식 저항성 평가

남태운,맹완영 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.8

Inconel alloys which have good high temperature mechanical properties and corrosion resistance have been used extensively as steam generator tube of nuclear power plants. There have been some reports on the intergranular stress corrosion cracking (IGSCC) failure problems in steam generator tubes of nuclear reactors. In order to evaluate the effects of heat treatment and composition on the IGSCC behavior of Inconel alloys in simulated nuclear reactor environment, four different specimens(Inconel 600 MA, 600TT, 690 MA and 690 TT) were prepared and tested by electrochemical method. Static potential tests for stressed C-ring type Inconel specimens were carried out in 10% NaOH solution at 300℃(75atm). It was found that IGSCC was initiated in Inconel 600 MA specimen, but the other three specimens were not cracked. Based on the gradients of corrosion current density of the four specimens as a function of test time, thermally treated alloys show better IGSCC resistance than mill-annealed alloys, and Inconel 690TT has better passivation characteristic than Inconel 600 MA. Inconel 690 TT shows clear periodic passivation that indicates good SCC resistance. The good IGSCC resistance of Inconel 690TT is due to periodic passivation characteristics of surface layer.