• The Korean Journal of Ceramics
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• v.5 no.2
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• pp.155-161
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• 1999

The tribological behaviour of monolithic SiC as well as SiC-TiC and SiC-TiC-$TiB_2$ particulate composite materials has been investigated in unlubricated oscillating sliding tests against $Al_2O_3$ at temperature in the range from room temperature up to $600^{\circ}C$. At temperatures below $600^{\circ}C$ the wear rate of the systems with the composite materials was up to 20 times lower than the wear of the $Al_2O_3$/SiC system and was dominated by the oxidation of the titanium phases. At $600^{\circ}C$ the oxidation rate of the TiC and -TEX>$TiB_2$ grains becomes predominant resulting in an enhanced wear rate of the composite rate of the TiC and TiB2 grains becomes predominant resulting in an enhanced wear rate of the composite materials. The coefficient of friction shows similar values for all materials of investigation, increasing from 0.25…0.3 at room temperature to 0.7…0.8 $600^{\circ}C$. The wear of the $Al_2O_3$/SiC system is mainly abrasive at temperatures above room temperature and is characterised by an enhanced wear of the alumina ball at $600^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.705-712
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• 1995

The wear characteristics and wear mechanisms in TiN coating deposited on high speed steel and alloy tool steel by ion plating were investigated. Pin on V-block wear tester was used for a wear test method. The specimen was composed of three kinds of high speed steel and alloy tool steel which had different hardness by changing the heat treating condition. Three kinds of coating thickness were also applied to each specimen. Microscopic observation of worn surfaces was made by SEM. The scratch test of coating surface by the ion plating showed that critical load to break the coating interface was greater than 50N. The critical load increased with both substrate hardness and coating thickness. The wear resistance of TiN coated high speed steel became 10 times greater than that of non-coated ones. SEM observation showed that leading edge of contact was compressive and trailing edge was under maximum tensile stress and then surface cracking broke out perpendicular to sliding direction.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.155-156
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• 2002

During the sliding between a-CNx and $Si_3N_4$, applying nitrogen as environmental gas provided very low friction as the level of 0.01 in friction coefficient. In order to know the effect of the running-in process on the reduction of the friction, the effect of surface roughness of mating surface on friction was investigated. It was shown that smooth surface in wear scar of ball provided low friction coefficient. Friction coefficient after running-in was proportional to the Ry value of wear scar of ball. Also smooth thin transferred layer was observed on the wear scar of balls with an AFM after sliding test. Those results showed the smoothing of wear scar of ball, the generating of the transferred layer from CNx was necessary for low friction.

• The Korean Journal of Ceramics
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• v.3 no.2
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• pp.96-100
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• 1997

Hydrogenated amorphous carbon films were deposited on silicon substrates by using an RF PECVD. The hydrogen/methane ratio was varied from 50% to 88% to study the effect of hytdrogen in the film on the tribological properties. The friction and wear behaviors of the deposited films were investigated by ball-on-disk type wear tester. FT-IR spectra were used to characterize the structure of the films. Tribological properties of carbon films were correlated with their structure such as ratio of "polymer-like" stretching type and that of sp2 bonding. The result showed that the annealing caused a decrease in the amount of wear of contacted $Si_3N_4$ balls and a increase in the coefficient of friction. Possible explanation for annealing effect was discussed by the hydrogen desorption.esorption.

• The Korean Journal of Ceramics
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• v.2 no.4
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• pp.212-215
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• 1996

This paper focuses the strength and wear resistance of CVD diamond films. The strength of free-standing CVD diamond films synthesized by microwave plasm CVD, DC plasma CVD, RF plasma CVD and arc discharge plasma jet CVD has been measured by three-point bending test. The wear resistance of CVD diamod films has been evaluated by the pin-on-disk type testing. diamond films coated on the base of sintered tungsten carbide pin by hot filament CVD have been rubbed with a sintered diamond disk in muddy water. Volume removed wear of CVD diamond has been compared with stellite, WC alloy and bearing steel.

• Tribology and Lubricants
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• v.19 no.4
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• pp.203-210
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• 2003

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 modified chemically by both epoxy and acrylic silane compounds. Friction and wear characteristics of the bonded solid lubricants, whose binders were of several hybrid ceramic materials, were tested with a reciprocating tribo-tester. Wear life was evaluated with respect to the heat-curing temperature, friction temperature, type of supplement lubricants, and ratio of binder materials. Test results showed that the Si-Zr hybrid ceramic materials modified by epoxy-silane compounds had a higher wear life compared to others. Sb$_2$O$_3$ was the most effective supplement lubricants in the high temperature, and BUS analyses revealed that it was caused mainly by a strong anti-oxidation effect to MoS$_2$ particles. The higher heat-curing temperature resulted in the higher wear life, and the higher friction temperature resulted in the lower wear life.

• Journal of Surface Science and Engineering
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• v.30 no.6
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• pp.400-405
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• 1997

The experimental study has been performed to deposit to deposit chromia powder on magnssium alloy for tribological and mechanical properties. The optimal condition was obtained by changing the spray condition such as working distance and gun power. As ceramics was coated onto the a light metal such as Mg according to the weight reduection of the car engine block, it could acquire that the engine efficiency deu to the weight reduction and properties such as resistance to heat, as well as wear. Coating qualities are discussed with respect to hardness, tribologicalproperty, and microstructure. The tribological and mechanical properties are investigated by using the reciprocal configuration tribometer and microharduess tester. Wear mode is determined by observing the SEM morhpology of wear track and cross section view of wear track.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1132-1133
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• 2006

Metal-bonded diamond impregnated tools are being increasingly used in the processing of stone and ceramics, road repair, petroleum exploration, etc. Although the main tool wear mechanisms have been identified, the scientific background is inadequate and fundamental research has to be carried out to better understand the tool field behaviour. This work addresses the complex issues of modelling abrasive wear of the metallic matrix under laboratory conditions. The generated data indicates that the matrix wear resistance can be assessed in a simple manner; whereas tests carried out on diamond impregnated specimens may aid prediction of the tool life in abrasive applications.

• Journal of Surface Science and Engineering
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• v.39 no.4
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• pp.179-189
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• 2006

High velocity oxygen fuel(HVOF) thermal spray coating of WC-Co powder is one of the most promising candidate for the replacement of the traditional hard chrome plating and ceramics coating because of the environmental problem of the very toxic $Cr^{6+}$ known as carcinogen and the brittleness of ceramics coating. WC-Co micron and nano powder were coated by HVOF thermal spraying method for the study of durability improvement of the high speed spindle. Coatings were planned by Taguchi program for the four spray parameters of spray distance, flow rates of hydrogen, oxygen and powder feed rate. Optimal coating process was obtained by the studies of coating properties such as porosity, surface roughness, micro hardness, and micro structure. WC-Co micron and nano powder were coated on the Inconel 718 substrate by the optimal coating process obtained in this study. The wear behaviors were studied by the sliding wear tester at room temperature and at an elevated temperature of $500^{\circ}C$ for the application to high speed spindle. Sliding wear test was carried out for four most promising hard coatings of chrome coating, ceramics coatings such as $A1_2O_3,\;Cr_2O_3$ and HVOF Co-alloy T800 for the comparison of their wear behaviors. HVOF WC-Co coating was better than other coatings showing highest micro hardness of 1400 Hv and comparable friction coefficients with others. HVOF WC-Co coating is a strong candidate for the replacement of the traditional hard chrome plating for the high speed spindle.

• Korean Journal of Materials Research
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• v.20 no.8
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• pp.444-449
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• 2010

Transparent ceramics are used in new technology because of their excellent mechanical properties over glasses. Transparent ceramics are nowadays widely used in armor, laser windows, and in high temperature applications. Silicon nitride ceramics have excellent mechanical properties and if transparent silicon nitride is fabricated, it can be widely used. h-BN has a lubricating property and is ductile. Therefore, adding h-BN to silicon nitride ceramics gives a lubricating property and is also machinable. Translucent silicon nitride was fabricated by hot-press sintering (HPS) and 57% transmittance was observed in the near infrared region. A higher wt. % of h-BN in silicon nitride ceramics does not favor transparency. The optical, mechanical, and tribological properties of BN dispersed polycrystalline $Si_3N_4$ ceramics were affected by the density, ${\alpha}:{\beta}$-phase ratio, and content of h-BN in sintered ceramics. The hot pressed samples were prepared from the mixture of $\alpha-Si_3N_4$, AlN, MgO, and h-BN at $1850^{\circ}C$. The composite contained from 0.25 to 2 wt. % BN powder with sintering aids (9% AlN + 3% MgO). A maximum transmittance of 57% was achieved for the 0.25 wt. % BN doped $Si_3N_4$ ceramics. Fracture toughness increased and wear volume and the friction coefficient decreased with an increase in BN content. The properties such as transmittance, density, hardness, and flexural strength decreased with an increase in content of h-BN in silicon nitride ceramics.