• Tribology and Lubricants
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• v.36 no.1
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• pp.18-26
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• 2020

The effects of the carburizing process on the sliding wear behavior of SCM420H steel have been investigated. In particular, the effects of grain boundary corrosion observed in the surface layer after gas carburizing and the effects of hardness of the carburized cases after heat-treatment on the sliding wear properties were examined. Pin specimens carburized by two methods (gas carburizing and vacuum carburizing) were tempered at two temperatures of 180℃ and 400℃ after oil-quenching, respectively. Sliding wear tests were carried out against heattreated SKH51 steel at several sliding speeds using a pin-on-disc type test machine. As results, it can be found that there is no difference in the wear behavior between the pins carburized using two methods. This implies that the grain boundary corrosion that formed in the surface layer after gas carburizing has no effect on the sliding wear behavior of carburized SCM420H steels. Additionally, there is no significant difference in the wear behavior between carburized pins tempered at 400℃ and at 180℃ after oil-quenching, regardless of the carburizing method. This is because carburized pins tempered at 400℃ have a troostite structure, which exhibits higher tribochemical reactivity even though its hardness is lower than that of martensite structure. In this respect, it can be considered that good wear resistance of carburized cases is maintained at least until the effective case depth.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.3
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• pp.270-278
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• 2009

Friction stir welding is a relatively new solid state joining process. A6061-T6 and A5052-H32 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio and good corrosion resistance. This friction stir process uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, etc., and tool pin profile play a major role in deciding FSP zone formation in A6061-T6 and A5052-H32 aluminium alloy. Three different tool pin profiles have been used to fabricate the dissimilar butt joints. The formation of friction stir processed zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the friction stir processed zone formation.

• Tribology and Lubricants
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• v.9 no.2
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• pp.63-69
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• 1993

The wear properties of two types of $Si_3N_4$(silicon nitride) exposed to high and low humidity were examined experimentally for various sliding speed. Bearing steel was used as the disk material at pin-on-disk type sliding. Wear rates of pressureless sintered-plus-hot-isostatic pressed Si3N4 were slightly lower than those of pressureless sintered $Si_3N_4$. It was observed that adsorbed moisture and sliding speed markedly influenced the wear properties of $Si_3N_4$. The highest wear rate was obtained under the high humidity and low sliding speed condition. As the sliding speed was increased, wear rates were decreased and the humidity effect on the wear rates of $Si_3N_4$ was lowered. The result that the $Si_3N_4$ pin showed a high wear rate under the high humidity condition was explained by the property change due to the adsorbed moisture, plowing action by the hard particles of $Fe_2O_3$ from the disk, and the corrosion effect at $Si_3N_4$ surface. Increase in sliding speed was supposed to have reduced the humidity effect on wear rate of $Si_3N_4$ by raising the temperature of both the bearing steel disk and $Si_3N_4$ pin specimen.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.22-28
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• 2008

Friction stir welding(FSW) is an relatively new solid state joining process. A1606l-T6 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio and good corrosion resistance. This friction stir process(FSP) uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, etc., and tool pin profile playa major role in deciding FSP zone formation in A16061-T6 aluminium alloy. Tow different tool pin profiles have been used to fabricate the joints. The formation of friction stir processed zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the friction stir processed zone formation.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.149-157
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• 2000

Tool wear in the shearing process such as blanking, piercing and trimming is very important, because it has great effects on the dimensional accuracy, working efficiency and economy. Most of tools in the shearing process have the coated layer at surface fur good wear and corrosion resistance. When the surface of tool is teated, the wear Phenomena of coated surface layer and inner layer may be different. This paper describes a computer modelling technique by the finite element method in order to investigate the wear mechanism and to predict the wear profile of Ti-N coated tool in piercing process according to the volume of Production. Wear coefficients of the coated layer and inner layer are obtained through Pin-on-Disk wear test, respectively. To verify the effectiveness of the suggested technique, the technique is applied to wear analysis in piercing recess of piston pin and simulation results are compared with experimental ones.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.89-90
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• 2006

Austenitic stainless steel has been used as a corrosion resistance material. However, austenitic stainless steel has poor wear resistance property due to its low hardness. In this investigation, we apply powder composite process to obtain hard layer of Stainless steel. The composite material was fabricated from planetary ball milled SUS316L stainless steel powder and WC powder and then sintered by Pulsed Current Sintering (PCS) method. We also added TiC powder as a hard particle in WC layer. Evaluations of wear properties were performed by pin-on-disk wear testing machine, and a remarkable improvement in wear resistance property was obtained.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.20 no.1
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• pp.49-55
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• 2024

Stainless 630 (or 17-4PH) is a precipitation-hardening martensitic stainless steel that has excellent mechanical properties and corrosion resistance. These characteristics make the STS630 to be used as a consisting material for various components such as spider, pin, spring, and spring retainer, of the control rod drive mechanism (CRDM) in pressurized water reactors (PWRs). In general, it is well known that the oxide layer of stainless steel consists of a duplex layer, a compact inner layer of FeCr₂O₄ spinel, and a coarse-grained outer layer of Fe₃O₄ spinel in PWR primary coolant condition. However, the characteristics of the oxide layer can be sensitively influenced by various water chemistry conditions such as temperature, dissolved oxygen, dissolved hydrogen, pH, pH adjuster type, and exposure time. In this work, we investigate the corrosion properties of the STS630 as a function of coolant temperature in an NH3 alkaline solution for its boron-free application in a small modular reactor, to confirm the feasibility for usage as a boron-free SMR structural material. As a result, oxide layer of corroded STS630 is consist of double-layer oxides consisting of a Cr-rich dense inner oxide and a Fe-rich polyhedral outer particles like as that in commercial PWR primary coolant. The corrosion rate of STS630 increases with increase in test time and temperature and the corrosion rate-time model equation was developed based on experimental data. Overall, it is expected that the results in this study provides useful data for the corrosion behavior of STS630 in alkaline environments, contributing to the development of selecting suitable materials for SMRs.

• Journal of the Korean institute of surface engineering
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• v.27 no.2
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• pp.74-82
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• 1994

The structure and properties such as adhesion and corrosion resistance of Cr and $Cr_2O_3$ films, deposited on steel plates by the vacuum evaporation method, were investigated. According to the ESCA and AES analy-sis, it could be concluded that chromium oxide with uniform composition could be formed on the steel sub-strate. The deposited Cr and $Cr_2O_3$ films had high adhesion strength, and they did not peeled off by the tape test. The adhesion property, however, was deteriorated as the film thciknes increased. After bending of the deposited specimen many cracks were observed by SEM, and they were assumed to have propagated along co-lumnar boundaries by the bending test. The corrosion resistance of the films was not generally good, which in-dicates that the films had a porous structure with a large number of defects such as pin holes and voids.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.55-57
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• 2005

Along with the development of the industrial society, as the transportation of water which is the indirect capital of society and petroleum, gas, etc used as energy sources is rapidly increased. the underground material is being expanded. Like this, the pipes laid under the ground not only bring the corrosion to the land circumstances to reduce the life of the pipes, but also raise the social problem of leakage accidents and the economic loss by Pin Hole. By reason of this, for the purpose of protecting the corrosion of the underground material, we are constructing and operating the electrolytic protection facilities. In case of a region of which specific resistance is high, however, we are not keeping proper protection potential(that is -850mV) to get protection effects. In this study, for the water pipes that under-voltage phenomena occur in the protection potential, we made a spot survey on the under-voltage section and normal-voltage section, compared, analyzed each of the contents and examined the under-voltage causes of the protection potential.

• Journal of the Korean Institute of Gas
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• v.5 no.1
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• pp.52-59
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• 2001

Factors to cause accidents were investigated through a systematic analysis of leakage accidents in welded LP-gas cylinder between 199 and 1999. As a result It was showed that most of leakage accident occurred at the pin-hole due to the localized corrosion on welded zone in cylinder. Accordingly, in this paper, we suggested that the problems of heat treatment condition in two-piece welded cylinder and substitute proposal for preventing the tearing of T zone in three-piece welded cylinder. Furthermore, corrosion rate on the weldment and base metal of welded LP-gas cylinder was evaluated using the electrochemical tests in acid rain and $3.5\%NaCl$ solution, Also, the poor adhesion and defects of film which was produced by electrostatic powder spray painting, while the LP-gas cylinder was manufactured, were analyzed using SEM(Scanning Electron Microscopy). And we proposed a optimum coating thickness of the cylinder.