• Tribology and Lubricants
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• v.11 no.5
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• pp.144-149
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• 1995

Use of high-quality basestocks is increasing to produce high-performance lubricants. However, their tribological characteristics have not been understood clearly yet. In this study, a newly developed basestock from a fuel hydrocracker and a poly-alpha-olefin are selected and investigated on the properties of lubricants formulated with them. The Lubricants are prepared by blending the basestocks with typical additives such as a zinc dialkyldithiophosphate, a dispersant, a detergent and a dispersant-inhibitor package. Frictional and wear-preventing properties are investigated using an oscillating-type wear-testing machine. The contact is a ball-on-disk mode and the testing temperature is varied from room temperature to 200$^{\circ}$C. The results show that their frictional property is varied significantly and that the non-conventional oils result in lower friction and lower wear compared with conventional lubricants, especially at the higher temperatures.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.131-132
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• 2007

• Composites Research
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• v.12 no.5
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• pp.12-22
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• 1999

Aluminum based metal matrix composites(MMCs) are well known for their high specific strength, stiffness and hardness. They are gaining further importance because of their high wear resistance. In this study wear behavior of $Al/Al_2O_3/C$ hybrid MMCs fabricated by squeeze infiltration method was characterized by the abrasive wear test under various sliding speeds at room and high temperature. Wear resistance of MMCs was improved due to the presence of reinforcements at high sliding speed. Especially wear resistance of carbon hybrid MMCs was superior to other materials because of its solid lubrication of carbon. The friction coefficient of MMCs was not affected by the sliding speed.

• Journal of the Korean institute of surface engineering
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• v.30 no.4
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• pp.272-280
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• 1997

The Thermal Barrier Coation(TBC) to improve the that barrier and wear resistant propenrty in high temperature ofthe aircraftength between the accumlation of the aircraft engine and the automobile engine has usually the two layer structure. One is a creamic top layer for heat insulation and the other is a metal bond layer to facilitate the bond strength between the top ceramic layer and the substrate. But, the coated layers should be peeled off because of the accumulation of the thermal stress by the differance of the thermal expantion coefficient between metal and ceramics in a hrat cyclic environment. In this study, the intermediate layer by plasm spray process was introduced to reduce the thermal stress. The powders of plasm spray coating were the Yttria Stabilized Zirconia (YSZ), the Magnesia Stabillized Zirconia(MSZ) and NiCrAlY. the intermediate layer was sprayed with the powders of the bond cast for the purpose of test were executed. The high temperature wear resistance tends to decreasnceee wear and thermal shock test were exeucuted. The high temperature were resistance of the YSZ TBC is better that of the MSZ TBC. The wearrsistance tends to decrease accoring to incresing the temperature between $400^{\circ}C$to $600^{\circ}C$. The thermal shock life of the 3 layer TBC with YSZ top casting was the most outstanding thermal shock rsisstasnce. This means that the intermediate layer should play an importnat roll to alleviate the diffrerence of the thermal expansion coef frcients between metallic layer and cermics layer.

• Proceedings of the Korean Vacuum Society Conference
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• 1995.06a
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• pp.151-151
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• 1995

Nitrogen implantation process has been applied for improvement of wear resistance of Z Zircaloy-4 fuel cladding materials. Nitrogen was implanted at 120 ke V to a total do range of 1xHP ions/cm2 to 8xlO17 ions/cm2 at various temperatures of 298"C to 676"C. The m microstructure changes by nitrogen implantation were analyzed by using TEM, XRD 뻐d A AES, cmd then wear behavior was evaluated by ball-on-disc wear testings at various loads a and sliding velocity under unlubricated condition. Nitrogen implantation produced ZrNx nitride above 4.37x1017 ions!cm2 as well as heavy d dislocations, which enhanced microhardness of the implanted surface of up to 900 Hk from 2 200 Hk of unimplanted substrate. Hardness was also found to be increased with increasing i implantation temperature and enhanced up to OOOHk at 620 "C. the wear resistance was g greatly improved with increasing total ion do않 as well as implantation temperature. The effective enhancement of wear resistance at high dose and tem야ratures is believed d due to significant hardening associated with high degree of precipitation of Zr nitrides and g generation of prismatic dislocation I$\infty$ps.infty$ps.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.14-20
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• 2003

The minimization of valve and seat insert wear is a critical factor in the pursuit of engine performance improvement. In order to achieve this goal, we have developed a new simulator, which can generate and control high temperatures up to $900^{\circ}C$ and various speeds up to 80Hz during motion, just like an actual engine. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity. The objective of this work focuses on the different degrees of wear from two different test speeds (10Hz & 25Hz). For this study, the temperature of the outer surface of the seat insert was controlled at $350^{\circ}C$, the cycle number was 2.1$\times$106, and the test load was 1960N. The wear depth and surface roughness were measured before and after the testing using a confocal laser scanner. It was found that a higher speed (25Hz) causes more wear than a lower speed (10Hz) under identical test conditions (temperature, cycle number and test load). In the wear mechanism adhesive wear, shear strain and abrasive wear could be observed.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.3
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• pp.134-140
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• 2003

Effects of cryogenic treatment and tempering temperature on the amount of retained austenite, hardness and wear properties has been investigated using alloy tool steel, STD 11. Cryogenic treatments were performed at the temperatures of $-100^{\circ}C$, $-150^{\circ}C$ and $-196^{\circ}C$, and tempering were performed at $200^{\circ}C$ and $530^{\circ}C$. It was shown that lower hardness value was obtained on high temperature ($530^{\circ}C$) tempering even after cryogenic treatment. And retained austenite was not entirely transformed to martensite after cryogenic treatment even at $-196^{\circ}C$, which was not consistent with the belief that $-80^{\circ}C$ was sufficient to entirely transform any austenite retained in the quenched microstructure. Austenite retained in cryogenic treated condition was completely transformed to martensite only after tempering at $530^{\circ}C$. As far as wear test conditions in this investigation, it was found that cryogenic treatments improved the sliding wear resistance, but improvement of wear resistance was not directly related with retained austenite contents. And it was found that predominent wear mechanisms of STD 11 steel were oxidation wear and adhesive wear In sliding wear conditions.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.372-377
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• 2000

Recently, fluid bearing have been studied to apply to spindle motors for hard disk drive, printer and others. Since fluid bearing have excellent stiffness and good load carrying capacity, the bearing proved to be suitable for those devices related to computer industry. In this paper, the friction and wear characteristics of the bearing were studied. The bearing appears good performance at a high temperature and high wear resistance.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.14-19
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• 1999

In order to evaluate the effect of Nb on wear properties of high speed steel by powder metallurgy(PM-HSS), niobium-alloyed PM-HSS have been prepared by adding 0%, 1%, 3% and 5%Nb to PM-HSS of 6%W-5%Mo-4%Cr-5%V-5%Co presented in the previous paper. Sliding wear test have been conducted in various sliding speed conditions under the constant pressure using a pin-on-disc type machine. The results of this study shows that the wear resistance of PM-HSS has been increased by the addition of Nb in the range of experimental sliding speed. However, the amount of Nb shows to be unimportant parameter for the improvement of the wear resistance. It may be due to the thermal stability of carbide and high temperature properties of matrix by adding Nb comparing to the case of no addition.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.5
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• pp.77-83
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• 2022

A high-hardness tool material is required to reduce extreme abrasive wear when drilling carbon fiber reinforced plastic (CFRP). Single-crystal diamond is the hardest material in the world, but it is very expensive to be used as a cutting tool. Polycrystalline diamond (PCD) is a diamond grit fused at a high temperature and pressure, and diamond-like carbon (DLC) is an amorphous carbon with high hardness. This study compares DLC coatings and PCD inserts to conventional TiAlN-coated tungsten carbide drills. In fiberglass and carbon fiber reinforced polymer drilling, the tool wear of DLC-coated carbide was approximately half that of TiAlN-coated tools, and slight tool wear occurred in the case of PCD insert end drills.