• Corrosion Science and Technology
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• 제20권1호
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• pp.22-25
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• 2021

In the past, Alloy 600 nickel-based alloys have been widely used in steam generators. However, most of them have been replaced by thermally treated alloy 690 tubes in recent years because mill annealed alloy 600 materials are known to be susceptible to stress corrosion cracking. Unlike this general perception, some steam generators using mill annealed alloy 600 tubes show excellent performance even though they are designed, manufactured, and operated in the same way. Therefore, various analyses were carried out to determine causes for the degradation of steam generators. Based on the general stress corrosion cracking mechanism, tube material susceptibility, residual stress, and sludge deposits of steam generators were compared to identify factors affecting stress corrosion cracking. It was found that mill annealed alloy 600 steam generator tubes showed higher resistance to stress corrosion cracking when the amount of sludge deposits on tube surface was smaller and residual stress generated during the fabrication was lower.

• 연구논문집
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• 통권28호
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• pp.183-192
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• 1998

The wear and oxidation resistance of two phase nickel aluminides was investigated. Wear tests of various heat-treated specimens at room temperature and at $500^{\circ}C$ were performed under no lubricant condition in air by using a ball-on-disk type tribotester. Isothermal oxidation tests were made at $1100^{\circ}C$ in air flowing at the rate of 70cc/min and at $1000^{\circ}C$ in air by using TGA. Experimental results from wear tests showed that nickel aluminide with a higher content of Al had an improved wear resistance at both temperatures. Also the examination of the wear tracks after wear test at both room temperature and $500^{\circ}C$ indicated that regardless of the alloy compositions the wear tracks of the two phase nickel aluminides showed an abrasive type wear The improved oxidation resistance observed in the Ni-34at%Al alloy could to be attributed to the microstructural difference between the aluminides. An accelerated oxidation along the thin layer of $Ni_3AL$ along the grain boundary observed in the microstructure of the Ni-32at%Al aluminide could be attributed to the poor oxidation resistance.

• Corrosion Science and Technology
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• 제2권2호
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• pp.59-67
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• 2003

Electrochemical potentiokinetic reactivation (EPR) tests are used to evaluate the degree of sensitization (DOS) of stainless steels and nickel base alloys. The validity of EPR test to detect DOS of these alloys, however, depends all the electrolyte composition employed. The existence of precipitates such as NbC, and TiC, etc. in the alloys also affects the reactivation behaviors of these alloys. In this investigation, the reactions involved during EPR processes are analyzed. In 0.5 M $H_2SO_4$+ 0.01 M KSCN electrolyte, a reactivation peak associated with the localized attack around NbC, different from that of intergranular corrosion, is observed for the solution annealed 347 SS. For solution annealed Alloy 600, matrix corrosion and localized attack around TiC with distinct anodic peaks appeared in the EPR curves are seen in the $H_2SO_4$+ KSCN electrolyte. With proper adjustment of elect rolyte composition, the contribution from intergranular corrosion, as a result of chromium carbide precipitation along the grain boundaries, can be distingui shed from the matrix and localized corrosion for the sensitized Alloy 600.

• 한국주조공학회지
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• 제3권3호
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• pp.174-180
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• 1983

The matrix changes and graphite formation in high manganese cast iron (Fe-12Mn-3.5C) are studied with increasing nickel and silicon content. Also, the decomposition of carbides and graphite precipitation are studied by adequate heat treatment.The results obtained in this work are as follows. 1. In high manganese cast iron, fine flakes graphite appeared by adding 5 wt% nickel and A-type flakes graphite can be obtained by adding 7 wt% nickel. 2. Nodular graphite are obtained by graphite spheroidizing treatment with same melt. 3. In high manganese cast iron containing 7 wt% nickel, full austenitic matrix with nodular graphite can be achieved by water quenching after 10 hours' solution heat treatment at $1050^{\circ}C$ in case of containing 2.0 wt% silicon, and 6 hours' at the same temperature in case of containing 2.5 wt% silicon.

• 한국표면공학회지
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• 제21권4호
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• pp.168-175
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• 1988

The nickel0zinc allot depositions have been studjen in ammonium chloridw added chloride baths to fine out the effects of ultrasonic irradiation for the electrodeposition processes. The compositions of deposited alloys, the current efficiencies, corrosion resistance and brightness in various conditions of electrodeposition were investigated, in the range of ultrasonic irradiation of 50,500 and 1,000kc/s respectively. The results obtained are as follows; 1. the ratio of nikel to zinc in the deposit increased according 시 the ammonium chloride concentration in irradiated baths. 2. The current efficiencies became also higer in the irradiated bath. 3. Ammonium ions in solution seem to retard formation of zinc hydroxide. 4. The corrsion resistance and brightness of the deposits are dependent upon nickel content of deposits which ranges 10-18%(wt)nickel in the irradiated baths and 11-15%(wt)in ninirradisted baths. 5. The corrosion resistance and brightnes of the deposited are appreciably better in the irradiated baths than in non-irradiated bath with the mole ratio of 3.4(NH+4/Ni+++Zn++).

• 한국표면공학회지
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• 제32권2호
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• pp.157-164
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• 1999

In this study the effect of nickel addition on the coating weight of mini-mill steels containing silicon has been studied. It is shown that the pure zinc accelerated growth of the alloy layers occurred by a rapid growth of the zeta phase at 0.06%Si. The addition of 0.06%Ni to a pure zinc bath was found to be very effective in reducing the coating weight and promoting preferential development of the delta phase. The coating obtained by immersion in the Zn-Ni bath shows the presence of a nickel-rich region between the zeta phase and the eta phase. It is suggested that nickel prevents the rapid growth of the zeta phase due to the formation of the Zn-Ni-Fe ternary compound, which may act as a barrier to inward diffusion of zinc or iron at the zeta-eta boundary.

• 동력기계공학회지
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• 제4권2호
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• pp.31-39
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• 2000

Relationships between the plating condition and the plating rate of the deposition film for the electroless plating of Co-Cu-P alloy were discussed in this report. The result obtained from this experiment were summarized as follow ; The optimum bath composition was consisted of 0.8 ppm thiourea as a stabilizing agent. Composition of the deposit was found to be uniform after two hours of electroless plating. Plating rates of nickel-catalytic surface and zincate-catalytic surface were found to be very closely equal, but the plating time of nickel-catalytic surface took longer than that of the zincated-catalytic surface.

• 한국기계가공학회지
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• 제9권2호
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• pp.1-5
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• 2010

According to the high demand of hybrid components, the hybrid materials development and processing technology were increased in the industry field. Although hybrid materials have various machining technologies, the research about them has rarely been proceed. This study is to carry out results about design technology of miniaturized high-speed air spindle and machining characteristics of hybrid materials using that. We studied machining characteristics in Nickel-Chrome alloy(Ni-Cr) according to change rotating speed using miniaturized high-speed air spindle. As the following results, the change of surface shape and roughness was investigated as the processing conditions such as rotating speed of miniaturized high-speed air spindle.

• 한국표면공학회지
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• 제38권4호
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• pp.156-162
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• 2005

Nickel-iron nanocrystalline alloys with different compositions and grain sizes were fabricated by electro-plating for MEMS devices. The iron content of the deposits was changed by varying the nickel/iron ion ratio in the electrolyte. X-ray diffraction (XRD) analysis was applied for measuring the strength of the texture and grain size of the deposits. The nickel/iron atom ratio of the deposits was analyzed by EDS. The hardness of the alloys was evaluated by Vickers hardness indenter. The internal stress of the deposits was measured by Thin Film Stress Measurement using Stoney's formula. Surface morphology and roughness were investigated by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The results of this study revealed that at a grain size of approximately $17\~24$nm the hardness, internal stress and roughness depend strongly on the iron content. With increasing the iron content, the hardness and internal stress of the deposits increased. An excellent correlation between the increase in the internal stress and the loss of (200) texture was found.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 추계학술발표회 발표논문집
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• pp.995-996
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• 2004