• The Journal of Korean Academy of Prosthodontics
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• v.45 no.5
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• pp.611-620
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• 2007

Statement of problem: Second-generation indirect composite resins have been improved flexural strength, compressive strength, hydrolytic degradation resistance, wear resistance compared to first-generation indirect composite resins, but there are still some problems as hydrolysis and low wear resistance. Some manufacturers claim that wear resistance of their materials has been improved, but little independent study has been published on wear properties of these materials and the properties specified in the advertising materials are largely derived from in-house or contracted testing. Purpose: This study was to evaluate the wear of indirect composite resins (SR Adore, Sinfony, Tescera ATL) and gold alloy against the human enamel. Material and method: Extracted human incisors and premolars were sectioned to $2{\times}2{\times}2mm$ cube and embedded in the clear resin and formed conical shaped antagonist to fit the jig of pin-on-disk tribometer. Total 20 antagonists were stored in distilled water. Five disk samples, 24mm in diameter and 1.5mm thick, were made for each of three groups of indirect composite resins and gold alloy group, and polished to #2,000 SiC paper on auto-polishing machine. Disk specimens were tested for wear against enamel antagonists. Wear test were conducted in distilled water using a pin-on-disk tribometer under condition (sliding speed 200rpm contact load 24N, sliding distance 160m). The wear of the enamel was determined by weighing the enamel antagonist before and after test, and the weight was converted to volumes by average density. The wear tracks were analyzed by scanning electron microscopy and surface profilometer to elucidate the wear mechanisms. Statistical analysis of the enamel wear volume, wear track depth and wear tract width of disk specimens were accomplished with one-way ANOVA and the means were compared for significant differences with Scheffe's test. Results: 1. The enamel wear was most in gold alloy, but there were no statistically significant differences among all the groups (P>.05). 2. In indirect composite resin groups, the group to make the most shallow depth of wear tract was Sinfony, followed by Tescera ATL, SR Adoro (P<.05). Gold alloy was shallower than Sinfony, but there was no statistically significant difference between Sinfony and gold alloy (P>.05). 3. The width of wear tract of SR Adore was larger than the other groups (P<.05), and there were no statistically significant differences among the other groups (P>.05). 4. SEM analysis revealed that Sinfony and gold alloy showed less wear scars after test, Tescera ATL showed more wear scars and SR Adore showed the most. Conclusion: Within the limits of this study, Sinfony and gold alloy showed the least wear rates and showed similar wear patterns.

• Tribology and Lubricants
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• v.17 no.5
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• pp.380-385
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• 2001

In nuclear power steam generators, high flow rates can induce vibration of the tubes resulting in fretting wear damage due to contacts between the tubes and their supports. In this paper the fretting wear tests and the sliding wear tests were performed using the steam generator tube materials of Inconel 600 and 690 against STS 304. Sliding tests with the pin-on-disk type tribometer were done under various applied loads and sliding speeds at air environment. Fretting tests were done under various vibrating amplitudes and applied normal loads. From the results of sliding and fretting wear tests, the wear of Inconel 600 and 690 can be predictable using the work rate model. Depending on normal loads and vibrating amplitudes, distinctively different wear mechanisms and often drastically different wear rates can occur. It was found the results that the wear coefficients for Inconel 600 and 690 were 262.3$\times$10$\^$-15/Pa$\^$-1/ and 209.2$\times$10$\^$-15/Pa$\^$-1/, respectively. This study shows that Inconel 690 can provide much better wear resistance than Inconel 600 in air.

• Journal of Surface Science and Engineering
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• v.46 no.6
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• pp.264-270
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• 2013

Effects of preoxidation on high temperature wear of piercing plug tool steel sliding against SA210C steel used for production of seamless tube have been studied using a pin-on-disc CETR tribometer, under applied normal load of 20 N at $900^{\circ}C$ in air. It was found in the preoxidized pin specimens of piercing plug tool steel that the coefficient of friction decreased to about 0.4 at an initial stage followed by showing nearly constant value of about 0.4 during high temperature wear testing. On the other hand, it was also found in the pin specimens without preoxidation that the coefficient of friction increased and fluctuated, ranging from about 0.3 to 0.6 during the tests until the running period of about 800 sec. The compact and continuous Fe-oxide layer was formed on the contact surface of the preoxidized pin specimens after high temperature wear testing followed by penetrating along the grain boundaries of coarse ferrite in the decarburized region beneath the oxide layer due to the lower hardness of the region.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.127-127
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• 2012

나노결정질 다이아몬드(Nanocrystalline Diamond: NCD) 박막은 고경도와 낮은 마찰계수를 가지고 있어 고속도강과 같은 절삭공구 위에 코팅하여 공구의 성능 향상을 도모하고자 하는 노력이 있어 왔다. 그러나 NCD 박막의 잔류응력이 크고, 철계금속에는 NCD가 증착되지 않는다는 문제점이 있다. 잔류응력 완화와 다이아몬드 핵생성을 위하여 제3의 중간층 재료가 필요하다. 본 연구에서는 Ti과 W을 중간층으로 하여 고속도강(SKH51)에 NCD 박막을 코팅하고 기계적 특성을 비교하였다. 고속도강 위에 DC 마그네트론 스퍼터를 이용하여 2 ${\mu}m$ 두께의 Ti 또는 W 중간층을 증착하고, 그 위에 Microwave Plasma Chemical Vapor Deposition (MPCVD) 방법으로 NCD 박막을 2 ${\mu}m$ 두께로 코팅 한 것과 Ti, W순으로 각각 1 ${\mu}m$ 두께로 증착 후 그 위에 NCD 박막을 2 ${\mu}m$ 두께로 코팅 한 시편을 비교하였다. 세 가지 종류의 시편에 대하여 FESEM을 이용하여 표면과 단면의 형상을 관찰하였고, XRD와 Raman spectroscopy를 통해 NCD 박막의 결정성을 확인하였다. 그리고 Tribometer를 이용해 코팅된 박막의 내마모성을 비교하였으며 Rockwell C Indentation test를 이용하여 접합력을 비교하였다. 연구 결과 Ti/W 복합중간층 위에 코팅된 NCD의 접합력이 가장 우수하였으며 그 다음 W, Ti 순으로 나타났다. NCD와 고속도강의 큰 열팽창계수 차이가 복합중간층으로 인해 줄어들고 잔류응력이 완화되어 접합력이 향상되는 것으로 여겨진다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.1
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• pp.36-40
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• 2003

The diamond-like nanocomposite (DLN) thin films were deposited on Si substrates using $CH_4/(C_2H_5O)_4Si/H_2$/Ar gas mixtures as source gases by the plasma enhanced chemical vapor deposition (PECVD). The chemical structure and microstructure of grown films were investigated and their tribological properties were evaluated by a ball-on-plate type tribometer. The deposited DLN films mainly consisted of diamond-like a-C:H and quartz-like a-Si:O networks. The DLN films had a good agreement with tribological coating applications due to their extremely low friction coefficients and low wear rates.

• Carbon letters
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• v.26
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• pp.51-60
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• 2018

An electroless deposition method was used to modify the surface properties of rice husk ceramic particles (RHC) by depositing nano-nickel on the surface of the RHC (Ni-RHC). The dry tribological performances of aluminum matrix composite adobes containing different contents of RHC and Ni-RHC particles have been investigated using a micro-tribometer. Results showed that the Ni-RHC particles substantially improved both the friction and wear properties of the Ni-RHC/aluminum matrix adobes. The optimal concentration was determined to be 15 wt% for both the RHC and Ni-RHC particles. The improvements in the tribological properties of aluminum adobes including the Ni-RHC were ascribed to friction-induced peeling off of Ni coating and formation of protection layer on the wear zone, both of which led to low friction and wear volume.

• Tribology and Lubricants
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• v.26 no.4
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• pp.246-253
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• 2010

Friction characteristics of the brake friction materials without environmentally regulated ingredients were examined to find their role in the brake performance. Five friction materials were produced based on a nearcommercial formulation by changing the relative amount of potentially hazardous ingredients to health and environment, such as $Sb_2S_3$, potassium titanate, and brass fiber. Tribological properties of the friction materials were obtained using a scale dynamometer and Krauss type tribometer. Results showed that the excluded three ingredients played important synergetic effects on tribological properties in terms of fade resistance, wear resistance and friction effectiveness. In particular, brass fibers played important roles in the friction stability by providing excellent thermal diffusivity at the friction interface. Potassium titanate whiskers showed excellent fade resistance and wear resistance compared to the substituted barite. Antimony trisulfide, on the other hand, showed little effect on the high temperature fade resistance and wear resistance, while it increased friction effectiveness at moderate temperatures. The friction materials without the three ingredients showed severe fade, indicating antisynergy effects.

• Tribology and Lubricants
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• v.21 no.6
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• pp.278-282
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• 2005

Deep groove ball bearing is installed in a control element of an integral nuclear reactor, where water is used as coolant and lubricant. This bearing is made of STS440C stainless steel for the raceways and the balls to use in radioactive environment and water. It is known that the retainer design affects ball bearing operability and endurance life, however there is no verified retainer design and material for water lubricated ball bearing. Four kinds of retainers are manufactured for the endurance test of water lubricated deep groove ball bearing. Three of them are commercially developed types and the other is designed for this research. It is verified that ball bearings with steel pressed and general plastic retainer can not survive to required life in the water, however bearings with machined type and cylinder type retainer can survive. This proves that one of the major design parameters for water lubricated ball bearing is retainer type and material. In this paper, experimental research of endurance test for water-lubricated ball bearing are reported.

• Tribology and Lubricants
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• v.19 no.6
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• pp.321-328
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• 2003

In the present study, the residual stresses can have a significant on the life of structural engineering components. Residual stresses are created by the surface treatment such as shot peening or deep rolling. The objective of this experimental investigation is to study the influence of friction and wear characteristics due to residual stress under dry sliding condition. Friction and wear data were obtained with a specially designed tribometer. Test specimens were made of SUP9 (leaf spring material) after they were created residual stress by shot peening treatment. Residual stress profiles were measured at surface by means of the X­ray diffraction. Sliding tests were carried out different contact pressure and same sliding velocity 0.035 m/s (50 rpm). Leaf spring assembly test used to strain gauge sticked on leaf spring specimen in order to measure interleaf friction of leaf spring. Therefore, we were obtained hysteresis curve. As the residual stresses of surfaces increased, coefficient of friction and wear volume are decreased, but the residual stresses of surfaces are high, and consequently wear volume do not decreased. Coefficient of friction obtained from leaf spring assembly test is lower than that obtained from sliding test. From the results, structural engineering components reduce coefficient of friction and resistant wear in order to have residual stresses themselves.

• Tribology and Lubricants
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• v.12 no.3
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• pp.12-25
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• 1996

The friction and wear behaviors of ceramics against steels with lubricants were investigated and compared with those observed in air. Lubrications wbre done by a water and a commercial engine oil as received. The investigated ceramics were $Al_{2}O_{3}$, SiC, and $Si_{3}N_{4}$. Steels with 0.2 wt.% C were heat treated to obtain tempered structure. A cylinder-on-plate tribometer with rotated sliding motion was used to carry out the experiments. In the experiments reported here, the ranges of different testing speeds and loads were used. It was found that the friction and wear characteristics of tested pairs were significantly influenced by environments. In water and oil environments the wear of ceramics was reduced from 10$^{-6}$ g/s down to 10$^{-8}$ g/s in dry sliding at the same values of the frictional power which are the products of the friction coefficient, the load and the sliding speed. SiC showed excellent wear resistant behavior in water sliding, which was the lowest among tested ceramics, but it was, very poor in oils. In case of $Si_{3}N_{4}$, the wear rates were very low under oil environment, but the highest in water. The wear rates of $Al_{2}O_{3}$ were very low in both lubricating conditions at low values of the frictional power, but high at high values of the frictional power.