• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.21-28
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• 2009

Purpose: The purpose of this study was to compare the wear characteristics of human enamel opposing 2 heat-pressed ceramics (e.max Press and Empress Esthetic), conventional feldspathic porcelain (Ceramco 3) and type III gold alloy. Material and methods: Intact cusps of extracted premolars were used for enamel specimens. Five disk samples were made for each of two heat-pressed ceramics groups, conventional feldspathic porcelain group and type III gold alloy group. Wear tests were conducted in distilled water using a pin-on-disk tribometer. The amount of enamel wear was determined by weighing the enamel specimens before and after wear tests, 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 characteristics. Results: 1. Ceramco 3 led to the greatest amount of enamel wear followed by Empress Esthetic, e.max Press and type III gold alloy. However, there was no significant difference between Ceramco 3 and Empress Esthetic (P>.05), and there were also no significant differences among Empress Esthetic, e.max Press and type III gold alloy (P>.05). 2. The average surface roughness of e.max Press after wear test was smallest followed by Empress Esthetic and Ceramco 3, but there was no significant difference between Empress Esthetic and Ceramco 3 (P>.05). 3. There were no significant differences among the depth of wear tracks of all the groups (P>.05). The group that showed the largest width of wear track was Ceramco 3 followed by Empress Esthetic, e.max Press and type III gold alloy. However, there was no significant difference between e.max Press and Empress Esthetic (P>.05), and there was also no significant difference between Empress Esthetic and Ceramco 3 (P>.05). Conclusion: Within the limits of this study, heat-pressed ceramics were not more abrasive than conventional feldspathic porcelain.

• Tribology and Lubricants
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• v.11 no.3
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• pp.11-23
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• 1995

The friction and wear behavior of $Al_{2}O_{3}$, SiC, and $Si_{3}N_{4}$ under the different sliding conditions were investigated. The cylinder-on-disc wear tester was used for a wear test method. Using the servo-motor, the sliding speed did not alternate due to the frictional forces. Three kinds of loads were selected to watch the variation of the wear rates and the frictional forces under a constant speed. Three kinds of sliding conditions were used to see the effects of the oxidation and the abrasion. The dominant wear mechanisms of $Al_{2}O_{3}$ were the abrasion and the formation of transfer layers. The abrasion has a great effect on the wear of SiC. The wear of $Si_{3}N_{4}$ was due to the asperity-failure and the oxidation. Also, the wear rate of each ceramic is shown to be related to the frictional power provided to the tribological system.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.63-70
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• 1999

Surface hardening of plain carbon steel (SM45C) by Laser are usually much finer and stronger than those of the base metals. The present study was under taken to investigate the wear resistance and a processing parameters such as, power density, pulse width, defocusing distance, and molten depth for surface modification of plain carbon steel. The wear test was carried out under experimental condition using the wear test device, and in which the annular surfaces of wear test specimens as well as mating specimen of alumina ceramics($Al_2O_3$) was rubbed in dry sliding condition. It is shown that molten depth and width depend on defocusing distance. The wear loss on variation of sliding speed was much in lower speed range below 0.2m/sec and in higher speed range above 0.7m/sec, but wear loss was little in intermediate speed range. It depends on oxidation speed and wear speed.

• Journal of the Korean Ceramic Society
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• v.54 no.4
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• pp.292-297
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• 2017

${\beta}-SiAlON$, based on its high fracture toughness, good strength and low abrasion resistance, has been adopted in several industrial fields such as bearings, turbine blades and non-ferrous metal refractories. In general, ${\beta}-SiAlON$ is fabricated by reactive sintering using expensive $Si_3N_4$ and AlN as starting materials. On the other hand, in this study, a cheaper ${\beta}-SiAlON$ starting powder synthesized by SHS was employed to improve price competitiveness compared to that of the reactive sintering process. ${\beta}-SiAlON$ ceramics with various content of the sintering additive $Y_2O_3$ up to 7 wt% were fabricated by conventional pressureless sintering at $1800^{\circ}C$ for 2 to 8 h under $N_2$ pressure of 0.1 MPa. The specimen with 3 wt% $Y_2O_3$ exhibited the best mechanical properties: hardness of 14 GPa, biaxial strength of 830 MPa, fracture toughness of $5MPa{\cdot}m^{1/2}$ and wear rate of about $3{\times}10^{-6}mm^3/N{\cdot}m$.

• Journal of the Korean Professional Engineers Association
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• v.22 no.2
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• pp.10-18
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• 1989

New Materials such as fine ceramics have attracted much attention as structural materials. The industrial needs of machining such materials will be emphasized more and more in the future. The objective of this study is to supply useful knowledges for improvement by cooled cutting of sintered diamond tool. This study treats with experimental analysis of tool wear, surface roughness and thermal stress which will lead to the machinability of fine ceramics.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.332-338
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• 1999

Surface hardening of plain carbon steel (SM$%C) by Laser are usually much finer and stronger than those of the base metals. The present study was undertaken to investigate the wear resistance and a processing parameters such as, power density, pulse width, defocusing distance, and molten depth for surface modification of plain carbon steel. The wear test was carried out under experimental condition using the wear test device, and in which the annular surfaces of wear test specimens as well as mating specimen of alumina ceramics(Al2O3) was rubbed in dry sliding condition. It is shown that molten depth and width depend on defocusing distance. The wear loss on variation of sliding speed was much in lower speed range below 0.2m/sec and in higher speed range above 0.7m/sec, but wear loss was little in intermediate speed range. It depends on oxidation speed and wear speed.

• Tribology and Lubricants
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• v.22 no.5
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• pp.282-289
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• 2006

This paper is to investigate the wear behaviors of two type ceramics, $Al_{2}O_{3}\;and\;TiO_{2}$, by coated plasma thermal spray method under the lubricative environment. The lubricative environments are grease fluids, a general hydraulic fluids, and bearing fluids. The wear testing machine used a pin on disk type. Wear characteristics, which were friction force, friction coefficient and the specific wear rate, according to the lubricative environments were obtained at the four kinds of load and sliding velocity is 0.2 m/sec. After the wear experiments, the wear surfaces of the each test specimen were observed by a scanning electronic microscope.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.215-225
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• 2002

In order to enhance the thermal stability of binder materials of bonded type solid lubricants, several combinations of metal-alkoxide based sol-gel materials such as methyltrimethoxysilane(MTMOS), $titaniumisopropoxide(Ti(Opr^{j})_{4})$, $zirconiumisopropoxide(Zr(Opr^{j})_{4})$ and $aluminumbutoxide(Al(Obu^{t})_{4})$ were chemically modified by epoxy-, acrylic- and fluoro-silane compounds, respectively, in this work. Friction and wear characteristics of these hybrid ceramic materials were tested with a micro tribe-tester where a reciprocating steel ball slid on a test material, and the tribological property was also evaluated with respect to both heat-curing temperature and tile time. Test results generally showed that hybrid ceramic materials modified by epoxy-silane compounds had a low friction compared to others. And the higher heat-curing temperature and the longer heat treatment time resulted in the higher friction and the lower wear. IR spectroscopic analyses revealed that it was caused mainly by the increased metal oxide content in hybrid ceramics when the heat-curing temperature was over $320^{\circ}C$.

• Tribology and Lubricants
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• v.18 no.5
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• pp.324-332
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• 2002

In order to enhance the thermal stability of binder materials of bonded type solid lubricants, several metal-alkoxide based sol-gel materials such as methyltrimethoxysilane(MTMOS), titaniumisopropoxide$(Ti(Opr^i)_4),$ zirconiumisopropoxide $(Zr(Opr^i)_4)$ and aluminumbutoxide$(Al(Obu^t)_4)$ were chemically modified by epoxy-, acrylic- and fluoro-silane compounds, respectively. Friction and wear characteristics of these hybrid ceramic materials were tested with a micro tribo-tester, and evaluated with respect to both heat-curing temperature and the time. Test results generally showed that hybrid ceramic materials modified by epoxy-silane compounds had a low friction compared to others. And the higher het-curing temperature and the longer heat treatment time resulted in the higher friction and the lower wear. IR spectroscopic analyses revealed that these results were caused mainly by the increased metal oxide content in hybrid ceramics when the heat-curing temperature was over $320^{\circ}C.$

• 연구논문집
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• s.28
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• pp.193-207
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• 1998

Fully dense THCN) based carbonitride ceramics were fabricated by pressureless sintering. During sintering, solid solutions were formed from the ceramic ingredients. The ceramics exhibited microvickers hardness of 1560-2050kgf/mm2, fracture toughness of 3.0-5.4 MPa $m^(1/2)$, and three point flexural strength of 645-1072 MPa. Some of the ceramics were shaped in a cutting tool, and the cutting performance was evaluated. In case of cutting SCM440 alloy steel, the ceramics showed better performance than the commercially available alumina-titanium carbide ceramic cutting tool. Considering the excellent productivity of pressureless sintering compared with other densification methods and their cutting performance, this new class of ceramics are very promising for wear resistant applications.