한국부식방식학회

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증기발생기 전열관 2차측 응력부식균열의 실험실적 모사 방법
In this work, it is aimed to develop the fabrication method of axial stress corrosion cracking (SCC) defects having various sizes, on the outer diameter surface of the steam generator (SG) tubings. To control the length of the artificial SCC defect, the specific area of the SG tubing samples was exposed to an acidic solution after a sensitization heat treatment. During the exposure to an acidic solution, a direct current potential drop (DCPD) method was adopted to monitor the crack depth. The size of the SCC defect was first evaluated by an eddy current test (ECT), and then confirmed by a destructive examination. From the comparison, it was found that the actual crack length was well controlled to be similar to the length of the surface exposed to an acidic solution (5, 10, 20 or 30 mm in this work) with small standard deviation. From in-situ monitoring of the crack depth using the DCPD method, it was possible to distinguish a non-through wall crack from a through wall crack, even though the depth of the non-through wall crack was not able to be precisely controlled. The fabrication method established in this work was useful to simulate the SCC defect having similar size and ECT signals as compared to the field cracks in the SG tubings of the operating Korean PWRs.
KEYWORDs : direct current potential drop method, eddy current test, non-through wall crack, steam generator tubing, stress corrosion cracking, through wall crack
AUTHORs : 이재민·김성우†·황성식·김홍표·김홍덕

Page : 107 - 111 DOWNLOAD
착화제와 pH가 무전해 Ni-Co-P 도금 피막의 석출거동에 미치는 영향
Electroless plated Ni-Co-P films have been used to suppress the electromagnetic waves from magnetic recording media, and the suppression is known to be achieved with films made with optimized plating composition and plating condition. Effects of complexing agents on the deposition rate and bath stability of Ni-Co-P film were studied using sodium citrate, sodium tartrate and multi-complex agents containing both of them. Deposition of electroless Ni-Co-P platings was dependent upon the complexing agents. Deposition rate was twice when using sodium tartrate compared to that using sodium citrate. And it was slightly slower with multi-complex agents than with sodium tartrate, bath stability being declined in the former. Deposition rate increased with increasing pH until pH 11. Excellent bath stability and good deposition rate were obtained using multi-complex agent as sodium citrate 0.10 mol/L and sodium tartrate 0.15 mol/L in the electroless Ni-Co-P plating films.
KEYWORDs : electroless plating, Ni-Co-P, deposition behavior, sodium citrate, sodium tartrate
AUTHORs : 최벽근·양승기·신지웅·황운석†

Page : 102 - 106 DOWNLOAD
Ni-Mn 전착층의 기계적 성질에 미치는 공정조건의 영향
Nickel electrodeposition from sulfamate bath has several benefits such as low internal stress, high current density and good ductility. In nickel deposited layers, sulfur induces high temperature embrittlement, as Ni-S compound has a low melting temperature. To overcome high temperature embrittlement problem, adding manganese is one of the good methods. Manganese makes Mn-S compound having a high melting temperature above 1500℃. In this work, the mechanical properties of Ni-Mn deposited layers were investigated by using various process variables such as concentration of Mn(NH2SO3)2, current density, and bath temperature. As the Mn content of electrodeposited layers was increased, internal stress and hardness were increased. By increasing current density, internal stress increased, but hardness decreased. With increasing the bath temperature from 55 to 70℃, internal stress of Ni deposit layers decreased, but hardness didn\'t change by bath temperature. It was likely that eutectoid manganese led to lattice deformation, and the lattice deformation increased hardness and internal stress in Ni-Mn layers. Increasing current density and decreasing bath temperature would increase a mount of H2 absorption, which was a cause for the rise of internal stress.
KEYWORDs : Ni-Mn, electrodeposition, internal stress, hardness, sulfamate bath
AUTHORs : 신지웅·양승기·황운석†

Page : 95 - 101 DOWNLOAD
산성 염화물 환경에서 F53 슈퍼 듀플렉스 스테인리스강의 2 상간의 공식 거동 연구
The pitting corrosion behaviors between the constituent phases in F53 super duplex stainless steel (SDSS) in acidified chloride environments were investigated using a critical pitting corrosion temperature test, a potentiodynamic anodic polarization test, and the microstructure analyses through a SEM-EDS and a SAM. As the solution annealing temperature decreased from 1150℃ to 1050℃, the γ-phase fraction increased whereas the α-phase fraction decreased. The pitting potential and the critical pitting temperature increased with a decrease of solution annealing temperature, thereby increasing the resistance to pitting corrosion. The pitting corrosion of the SDSS was selectively initiated at the α-phases because the PREN (pitting resistance equivalent number, PREN = %Cr+3.3%Mo+30%N) value of the γ-phase is much larger than that of the α-phase, irrespective of the solution annealing temperature. The pitting corrosion was finally propagated from the α-phase to the γ-phase. The decrease of solution annealing temperature enhanced the resistance to pitting corrosion greatly in acidified chloride environments due to a decrease of PREN difference between the γ-phase and the α-phase, that is, a decrease of PRENγ by dilution of N in γ-phase with an increase in the γ-phase volume fraction and an increase of PRENα by enrichment of Cr and Mo in the α-phase with a decrease in the α-phase volume fraction.
KEYWORDs : super duplex stainless steel, potentiodynamic polarization, critical pitting temperature, SEM-EDS, PREN
AUTHORs : 김순태†·공경호·이인성·박용수·이종훈·김두현

Page : 87 - 94 DOWNLOAD
원자력발전소용 316 스테인리스강 배관의 부식특성에 미치는 유도가열벤딩공정의 영향
Recently, the application of bending products has been increased since the industries such as automobile, aerospace, ships, and plants greatly need the usage of pipes. For facility fabrication, bending process is one of key technologies for pipings. Induction heat bending process is composed of bending deformation by repeated local heat and cooling. Because of local heating and compressive strain, detrimental phases may be precipitated and microstructural change can be induced. This work focused on the effect of induction heat bending process on the properties of ASME SA312 TP316 stainless steel. Evaluation was done on the base metal and the bended areas before and after heat treatment. Microstructure analysis, intergranular corrosion test including Huey test, double loop electropotentiokinetic reactivation test, oxalic acid etch test, and anodic polarization test were performed. On the base of microstructural analysis, grain boundaries in bended extrados area were zagged by bending process, but there were no precipitates in grain and grain boundary and the intergranular corrosion rate was similar to that of base metal. However, pitting potentials of bended area were lower than that of the base metal and zagged boundaries was one of the pitting initiation sites. By re-annealing treatment, grain boundary was recovered and pitting potential was similar to that of the base metal.
KEYWORDs : corrosion, 316 stainless steel, induction heat bending, nuclear power plant
AUTHORs : 신민철·김영식†·김경수·장현영·박흥배·성기호

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