• Tribology and Lubricants
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• v.29 no.6
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• pp.360-365
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• 2013

In this study, sliding wear tests were conducted to investigate the effects of tempered hardness on the sliding wear behavior of bearing steel. At a sliding speed of 0.3 m/s, the wear resistance of bearing steel with a tempered hardness of HRC 54 was superior to that with HRC 62. It was found that bearing steel with HRC 54 showed a strong tendency for the occurrence of oxidation wear at that speed, compared to that with HRC 62. This would be due to the troostitic structure of bearing steel with HRC 54, which is highly susceptible to corrosion. In this context, it is considered that sliding wear behavior could be affected by the corrosion resistance of the material.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.313-322
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• 1998

Tappet has wear problems like scuffing or pitting because of high Hertzian contact stress by line contact type between cam and tappet. To overcome this wear problems, we developed the high wear resistant tappet. Developed tappet consists of WC base alloyed tip and steel body. These two parts were directly bonded each other at high temperature under vacuum condition. To estimate the wear resistance of tungsten carbide tappet, we perform the scuffing test and engine dynamo test. As the result, tungsten carbide tappet has better wear resistance than conventionally chilled iron tappet.

• Korean Journal of Materials Research
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• v.11 no.10
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• pp.813-819
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• 2001

The microstructure and the distribution of hardness of Co and A1 alloy powder cladding layer in high carbon 9CrSi alloy steel for roll materials cladded by laser surface cladding were investigated. And, for the evaluation of soundness as the roll materials, we examined the wear resistance of the cladding materials with the wear appratus of pin on disc type. The experimental results showed that the microstructure of laser cladding layer was constituted with the clad surface layer, the alloy layer, the heat treatment layer with base metal. The wear resistance of Ni alloy Powder cladding material was superior to that of Co alloy powder cladding material both at the low speed (0.46m/s) and the high speed(0.92m/s). It seemed that the behavior of wear showed the abrasive wear at the early stage and the adhesive wear at the late stage.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.299-306
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• 2003

The SCM420 used mainly to automobile transmission gear has problems that it costs transmission gear maker much money in carburizing treatment. For this, it needs to alternate the existing material and heat treatment to new gear material and surface modification. For this, friction and wear experiment according to sliding speed and applied load was carried out to evaluate the wear resistance of two transmission gear materials with oxidation nitrocarburising and non-oxidation nitrocarburising NT100, The presumed wear volume was calculated with the image processing for evaluation of wear resistance of two transmission gear materials. The results show that the oxidation nitrocarburising has a distinguished wear resistance than non-oxidation nitrocarburising.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.4
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• pp.409-416
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• 2012

Recently, surface modification technology is of importance to improve the wear resistance and the corrosive resistance for high accurate mechanical parts such as LM guide, Ball Screw and Roller Bearing etc., Those has generally featured on rolling contact mechanism to improve not only the wear and the friction, but also the accuracy and the corrosion performances. For surface modifications of high accurate mechanical parts, normally thermal spray, PVD, CVD and E.P. processes have been used with many materials such as DLC, raydent, W, Ni, Ti etc. Diamondlike carbon (DLC) films possess a combination of attractive properties and have been largely employed to modify the tribological behaviors such as friction, wear, corrosion, fretting fatigue, biocompatibility, etc. However, for rolling contact mechanism mechanical parts DLC films are needed to study for commercial benefit. Rolling contact mechanism has features on effects of cyclic motions and stresses, and also not simply sliding motions. The papers focused on the performance test of wear and corrosive resistance according to Me-DLC film thickness. And also, its thickness effect of wear analysis was carried out through the simulation of the maximum shear stress under the rolling contact surface. As the results, Me-DLC films have more potential to improve the wear resistance for high precision mechanical parts than raydent films.

• Korean Journal of Materials Research
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• v.12 no.7
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• pp.550-554
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• 2002

The effect of Mn on cavitation erosion resistance and the sliding wear resistance of Fe-base hardfacing NewAlloy was investigated. Mn is known to decrease stacking fault energy and enhance the formation of $\varepsilon$-martensite. Cavitation erosion resistance for 50 hours and sliding wear resistance for 100 cycles were evaluated by weight loss. Fe-base hardfacing NewAlloy showed more excellent cavitation erosion resistance than Mn-added NewAlloys. $\Upsilon-\alpha$' phase transformation that can enhance erosion resistance by matrix hardening occurred in every specimens. But, only in Mn free Fe-base hardfacing NewAlloy, the hardened matrix could repress the propagation of cracks that was initialed at the matrix-carbides interfaces more effectively than Mn-added NewAlloy The Mn free Fe-base hardfacing NewAlloy showed better sliding wear resistance than Mn-added alloys. Mn-addition up to 5wt.% couldn't increase the sliding wear and cavitation erosion resistance of Fe-base hardfacing alloy because it didn't make $\Upsilon\to\varepsilon$ martensite phase transformation. Therefore, it is considered that the cavitation erosion and the sliding wear resistance can be improved due to $\Upsilon\to\varepsilon$ martensite phase transformation when Mn is added more than 5wt.% in Fe-base hardfacing alloys.

• Journal of Welding and Joining
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• v.35 no.2
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• pp.58-62
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• 2017

A319 aluminum alloy containing 6.5% Si and 3.5% Cu as major alloying elements has been widely used in machinery parts because of its excellent castability and crack resistance. However it needs more wear resistance to extend its usage to the severe wear environments. It has been known that hyper-eutectic Al-Si alloy having more than 12.6% Si contains pro-eutectic Si particles, which give better wear resistance and lubrication characteristics than hypo-eutectic Al-Si alloy like A319 alloy. In this study, it was tried to clad hyper-eutectic Al-Si alloy on the surface of A319 alloy. In the experiments, Al-36%Si alloy powder was mixed with organic binder to make a fluidic paste. The paste was screen-printed on the A319 alloy surface, melted by pulsed Nd:YAG laser and alloyed with the A319 base alloy. As experimental parameters, the average laser power was changed to 111 W, 202 W and 280 W. With increasing the average laser power, the melting depth was changed to $142{\mu}m$, $205{\mu}m$ and $245{\mu}m$, and the dilution rate to 67.2 %, 72.4 % and 75.7 %, and the Si content in the cladding layer to 16.2 %, 14.6 % and 13.7 %, respectively. The cross-section of the cladding layer showed very fine eutectic microstructure even though it was hyper-eutectic Al-Si alloy. This seems to be due to the rapid solidification of the melted spot by single laser pulse. The average hardness for the three cladding layers was HV175, which was much higher than HV96 of A319 base alloy. From the block-on-roll wear tests, A319 alloy had a wear loss of 5.8 mg, but the three cladding layers had an average wear loss of 3.5 mg, which meant that an increase of 40 % in wear resistance was obtained by laser cladding.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1619-1629
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• 1995

The Al/Al$_{2}$O$_{3}$ SiC and Al/Al$_{2}$O$_{3}$/C hybrid metal matrix composites (MMCs) were fabricated by squeeze infiltration method. Uniform distribution of reinforcements were found in the microstructure of metal matrix composites. Mechanical tests were carried out under various test conditions to clearly identify mechanical behavior of MMCs, and the wear mechanism of Al/Al$_{2}$O$_{3}$/(SiC or C) hybrid metal matrix composites were investigated. The tensile strength and hardness of hybrid composites was resulted in increasing compared with those of the unreinforced matrix alloy. Wear resistance was strongly dependent upon kinds of fiber, volume fraction and sliding speed. The wear resistance of metal matrix composites was remarkably improved by the addition of reinforcements. Especially, the wear resistance of the hybrid composites of carbon fibers was more effective than in the composites reinforced with alumina and SiC whiskers of reinforcements. This was due to the effect of carbon fiber on the solid lubrication. Wear mechanisms of hybrid composites were suggested from wear surface analyses. The major wear mechanism of hybrid composites was the abrasive wear at low to intermediate sliding speed, and the melting wear at intermediate to high sliding speed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.85-90
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• 2003

Although wear resistance of material improves with increasing its hardness, it is known that the wear resistance of steel is varied with hardness of counter material. In this context, wear properties of steel must be depended on the difference of hardness between the testpiece and the counter material. In this study, using the pin-on-disc type wear machine, annealed carbon steels were tested against ahoy tool steels with various levels of hardness. Then the changes of wear properties of carbon steel according to the hardness of counter material were investigated and the morphology of worn surface after test were evaluated. The results indicate that if there are no remarkable difference of hardness between them, wear resistance of carbon steel in running-in wear decreases with increasing the hardness of counter material. However, its wear properties at the range of high sliding speed have no relation with hardness of counter material. It is clear that wear properties is influenced by the formation of oxide of steel on their worn surface during wear.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.385-388
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• 2009

Dry-sliding-wear behavior of Fe-18Cr-l0Mn steel with various carbon and nitrogen contents was characterized, and the effect of carbon and nitrogen contents on the wear was investigated. Dry sliding wear tests of the steel were carried out at room temperature against an AISI 52100 bearing steel ball using a pin-on-disk wear tester. Applied wear loads were varied from 10 N to 100 N, and the sliding distance was fixed as 720 m. Worn surfaces and the wear debris of the steel were examined using an SEM to find out the wear mechanism. It was found that the Fe-18Cr-10Mn with both carbon and nitrogen exhibited superior wear resistance to the steel with only nitrogen. The wear resistance of the Fe-18Cr-10Mn-xC-yN alloy increased with the increase of the carbon content. The excellent wear resistance of the Fe-18Cr-10Mn-xC-yN alloy was explained by the increased strain-hardening capability with the interstitial atoms.