한국부식방식학회

Page : 33 - 38 DOWNLOAD
니켈 합금 모재 및 용접재의 일차수응력부식균열 균열성장속도 시험
Alloy 600/182 with excellent mechanical/chemical properties have been utilized for nuclear power plants. Although both alloys are known to have superior corrosion resistance, stress corrosion cracking failure has been an issue in primary water environment of nuclear power plants. Therefore, primary water stress corrosion
crack (PWSCC) growth rate tests were conducted to investigate crack growth properties of Alloy 600/182. To investigate PWSCC growth rate, test facilities including water chemistry loop, autoclave, and loading system were constructed. In PWSCC crack growth rate tests, half compact-tension specimens were manufactured. These specimens were then placed inside of the autoclave connected to the loop to provide primary water environment. Tested conditions were set at temperature of 360℃ and pressure of 20MPa. Real time crack growth rates of specimens inside the autoclave were measured by Direct Current potential drop (DCPD) method. To confirm inter-granular (IG) crack as a characteristic of PWSCC, fracture surfaces of tested specimens were observed by SEM. Finally, crack growth rate was derived in a specific stress intensity factor (K) range and similarity with overseas database was identified.
KEYWORDs : Primary water stress corrosion cracking, Crack growth rate, Inter-granular crack, Ni-base alloy, Nuclear power plants
AUTHORs : 이종훈†

Page : 24 - 32 DOWNLOAD
아연 코팅과 열처리에 따른 알루미늄 열교환기 소재의 부식
The effects of zinc coating and heat treatment on the corrosion resistance of aluminum alloys including A1100 and the modified A3003, used as heat exchanger tube were investigated in this study. The grain size of the heat-treated specimen is larger than that of the specimen without heat treatment, but the grain size did not significantly affect the corrosion behavior. The concentration of zinc was noted at 11.3 ~ 31.4 at.% for the as-received Zn-coated samples and reduced to 1.2 ~ 2.4 at.% after the heat treatment, as measured by the scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS) on the surface. The concentration of oxygen is 22 ~ 46 at.% for the zinc coated specimens while noted at 7.4 ~ 12.8 at.% for the specimens after the removal of the coating. The corrosion behavior depended largely on the concentrations of zinc, aluminum, and oxygen on the specimen surface, but not on the Mo content. The corrosion potential was high and the corrosion rate was low for a specimen with a low zinc content, a high aluminum content, and a high oxygen content.
KEYWORDs : Corrosion, Heat exchanger, Heat treatment, Zinc coating, Aluminum
AUTHORs : 조수연·김재중·장희진†

Page : 16 - 23 DOWNLOAD
Excellent Seam Weldable Nano-Composite Coated Zn-Ni Plating Steels for Automotive Fuel Tank
Steels for automotive fuel tank require unique properties such as corrosion resistance for fuel, welding for joining, forming for press, and painting for exterior. Recently, automakers have been requiring excellent seam weldable steels to enhance manufacturing productivity of fuel tank. Thus, POSCO developed a new
type of functional steels coated with nano-composite thin layer on Zn-Ni plating steels. The nano-composite coating solution was prepared by mechanical fine dispersion of solutions consisting of polymeric resin and nano-composite materials in aqueous media. The composite solution was coated on the plating steel surface
by using roll coater and cured through induction furnace. These new developed plating steels were evaluated for quality performances such as seam and spot weldability, press formability, and corrosion resistance. These new functional steels coated with nano-composite layer exhibited excellent seam weldability and press formability. Detailed discussion of coating solution and experimental results suggest that nano-sized composite dispersion as coating layer plays a key role in enhancing the quality performance.
KEYWORDs : Automotive fuel tank, Zn-Ni Plating steels, Corrosion resistance, Seam weld, Press forming
AUTHORs : Du-Hwan Jo†, Sang-Man Yun, Kee-Cheol Park, Myung-Soo Kim, and Jong-Sang Kim

Page : 8 - 15 DOWNLOAD
High Temperature Oxidation Behavior of Nickel and Iron Based Superallo in Helium Containing Trace Impurities
A high-temperature gas-cooled reactor (HTGR) is recognized as the best candidate reactor for next generation nuclear reactors. Helium is used to be the coolant in the core of the HTGR with temperature expected to exceed 900 °C at the core outlet. Several iron- and nickel-based superalloys, including Alloy 800H, Hastelloy X, and Alloy 617, are potential structural materials for intermediate heat exchanger (IHX) in
an HTGR. Oxidation behaviors of three selected alloys (Hastelloy X, Alloy 800H, and Alloy 617) were investigated at four different temperatures from 650°C to 950 °C under helium environments with various concentrations of O2 and H2O. Preliminary results showed that chromium oxide as the primary protective layer was observed on surfaces of the three tested alloys. Based on results of mass gain and SEM analyses, Hastelloy X alloy exhibited the best corrosion resistance in all corrosion tests. Further details on the oxidation mechanism of these alloys are presented in this study.
KEYWORDs : HTGR, Superalloys, Oxidation, Corrosion, Helium gas
AUTHORs : C. J. Tsai, T. K. Yeh, and M. Y. Wang†

Page : 1 - 7 DOWNLOAD
Effects of Surface Machining by a Lathe on Microstructure of Near Surface Layer and Corrosion Behavior of SA182 Grade 304 Stainless Steel in Simulated Primary Water
To find proper lathe machining parameters for SA182 Grade 304 stainless steel (SS), six kinds of samples with different machining surface states were prepared using a lathe. Surface morphologies and microstructures of near surface deformed layers on different samples were analysed. Surface morphologies and chemical composition of oxide films formed on different samples in simulated primary water with 100 μg/L O2 at
310 °C were characterized. Results showed that surface roughness was mainly affected by lathe feed. Surface machining caused grain refinement at the top layer. A severely deformed layer with different thicknesses formed on all samples. In addition to high defect density caused by surface deformation, phase transformation, residual stress, and strain also affected the oxidation behaviour of SA182 Grade 304 SS in the test solution. Machining parameters used for # 4 (feed, 0.15 mm/r; back ngagement, 2 mm; cutting speed, 114.86 m/min) and # 6 (feed,0.20 mm/r; back engagement, 1 mm; cutting speed, 73.01 m/min) samples were found to be proper for lathe machining of SA182 Grade 304 SS.
KEYWORDs : Surface machining, Cold-working, Microstructure, SS, Oxidation
AUTHORs : Zhiming Zhang, Jianqiu Wang†, En-hou Han, and Wei Ke

메인메뉴