• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.04a
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• pp.122-127
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• 1996

In this paper, the effects of the film tinckness, pre-treatment and testing load on. the tribological characteristics have been studied. During the "Ring on-Disk" testing period silica-gel was used to remove the effect of humidity. As a result, increasing the film thickness revealed prolonged wear life, in the case or reasl the testing loads the dynamic friction coefficient was decreased gradually but in regarding the wear life, an intermideate contact pressure (4kgf/mm${2}$) revealed the maximum value. In regarding the surface protuberance friction an intermediate value of area fraction (60%) revealed maximum wear life. In this paper, the qualitative model in regarding the variation of the friction coefficient andworn depth was presented.presented.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.175-176
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• 2002

Our study is to search for tribological properties of diamond-like carbon (DLC) films as known as anti- wear hard thin film on various polymers. This report deals with the deposition of DLC films on various polymer substrates in vacuum by magnetron radio frequency (RF) sputtering method with using argon plasma and graphite, titanium target. The properties of friction and wear are measured using a ball-on-disk wear -testing machine. The properties of friction and wear have been remarkably improved by DLC coating. Moreover the composition of DLC films has been analyzed by using auger electron spectroscopy(AES). The wear rate of titanium-containing DLC film is lower than that of no-metal-containing DLC film.

• Tribology and Lubricants
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• v.7 no.2
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• pp.61-66
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• 1991

The frictional and wear characteristics of non-asbestos friction materials made of four different fibers (carbon, aramid, ceramic and glass) have been investigated at elevated temperature using High Frequency Friction Tester. On the basis of the experimental results, friction and wear phenomena of four different non-asbestos fibers were caused by lattice layer film of carbon, polymeric transfer film of aramid, abrasion of ceramic and adhesion of glass fiber under each contact junction. The surface analysis of the worn specimens and counter parts after tests were observed using Scanning Electron Microscope and Optical Microscope.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.260-266
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• 2002

DLC films were deposited on Si wafer by RF plasma assisted CVD using CH4 gas. Tribological tests were conducted using rotating type ball on disk friction tester in dry air. Four kinds of mating balls were used. The mating balls were made with stainless steel but apply different annealing conditions to achieve different hardness conditions. Testing results in all load conditions showed that the harder the mating materials, the lower the friction coefficient among the three kind of martensite mating balls. In case of austenite balls, the friction coefficients were lower than fully annealed martensite ball. The high friction coefficient in soft martensite balls seems to be caused by the larger contact area between DLC film and ball. The wear tracks of DLC films and mating balls could have proven that effect. Measuring the wear track of both DLC films and mating balls have similar tendency comparing to the results of friction coefficients. Wear rate of austenite balls were also smaller than that of fully annealed martensite ball. The results of effect of applying load showed, the friction coefficients were become decrease when the applying loads exceed critical load conditions. The wear track of mating balls showed that some material transfer occurs from DLC film to mating ball during the high friction process. Raman spectra analysis showed that transferred material was a kind of graphite and contact surface of DLC film seems to undergo phase transition from carbon to graphite during the high friction process.

• Tribology and Lubricants
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• v.35 no.6
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• pp.389-395
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• 2019

In various industries, thin film coatings are used to improve friction and wear characteristics. Various types of tribotesters are used to evaluate the friction and wear characteristics of such thin film coatings. In this study, we fabricated a micro-tribotester and Tribo-scanning electron microscopy (SEM) to compare the friction and wear characteristics of copper (Cu) coatings under an atmospheric pressure and a vacuum condition, respectively. The reliability of the different types of tribotesters was evaluated by performing calibrations for the sensor to measure the friction forces and normal loads. Using the two different types of devices, the friction and wear tests are conducted at the same experimental conditions excluding environment conditions such as the atmospheric pressure and vacuum condition. The friction coefficient at the vacuum condition is lower than at the atmospheric pressure. This difference in friction characteristics is due to the fact that wear phenomena occur differently according to the atmospheric pressure and vacuum condition. At the atmospheric pressure, the abrasive wear is the main wear mechanism. At the vacuum condition, the adhesive wear is the main wear mechanism. The reason for the difference in the wear mechanism of the Cu coating at the atmospheric pressure and the vacuum condition is that the oxidation phenomenon, which does not appear at the vacuum condition, occurs at the atmospheric pressure; therefore, the characteristics of the Cu coating change accordingly.

• Tribology and Lubricants
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• v.18 no.4
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• pp.255-259
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• 2002

The tribological properties of eight different liquid crystals were investigated in a concentrated point contact device and a ball-on-flat contact. For comparison, the same tests were also performed with commercial greases and the corresponding base oils. Under the fully flooded conditions studied, liquid crystals in a concentrated point contact showed lower friction than commercial greases and greater film thickness dependence on rolling speed than grease base oils or greases. Test results also showed that the film thickness and friction were little influenced by the composition of the examined liquid crystals.

• Journal of the Korean Society of Safety
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• v.20 no.1 s.69
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• pp.18-23
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• 2005

This study deals with the friction and wear characteristics of C-N coated SCM415 steel. The PSII(plasma source ion implantation) apparatus was built and a SCM415 test piece with steel substrate was treated with carbon nitrogen by this apparatus. The composition and structure of the surface layer were analyzed and compared with that of PVD(physical vapor decomposition) coated TiN layer. It was found that both of friction coefficient of C-N coating and TiN coating decreased with increasing load, however, C-N coating showed relatively lower faction coefficient than that of TiN coating. The micro-vickers hardness of C-N film is 3200 Hv, which is $32\~43\%$ higher than that of TiN film. The critical load of C-N film is 52N, which is $25\%$ higher than that of TiN film. The hardness of C-N film fabricated by Plasma ion implantation is $61\~70\%$ higher than that of base material, and faction coefficient is $14\~50\%$ lower than that of base material. It is also interesting to note that the friction was changed from adhesive wear mode to light oxidizing wear mode.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.215-219
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• 1999

One of the innovative physical methods that provide insight into the basic processes which determine friction and wear behavior of coated machine tools is acoustic emission (AE). In this study, an investigation of the relation between AE and friction signal produced during repeated sliding test is presented. The material of test specimens is CrN coated 0.2% plain carbon steel with 1 Um thickness. The obtained results demonstrate that AE signal is very related with friction, and AE signal is more sensitive than friction when CrN coated film come off the substrate.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.04a
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• pp.99-107
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• 1996

Examined in this paper is the effect of B$_{4}$C addition on the frictional characteristics of Cu-Sn based sintered friction material. For the specimens 1%, 2% and 4% of B$_{4}$C were added into the reference material. A pin-on-disk type friction tester was used to measure the friction and wear with respect to the surface temperature and sliding distance. Wear mechanism of each specimen is analyzed in the view point of the oxide film formation. The specimen containing 4% of B$_{4}$C showed stable friction and low wear since the oxide film was sustained up to higher surface temperature ranges.

• Tribology and Lubricants
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• v.21 no.2
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• pp.77-82
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• 2005

In previous paper, the wear properties of clutch facing materials with two different copper amounts against fly-wheel materials used in the clutch system were investigated by sliding wear tests at different applied loads and speeds. This paper have been aimed to evaluate the friction properties for clutch facing materials at the same test conditions as the previous paper. The experimental results indicated that the friction properties of clutch facing materials are influenced from the thermal conductivities of the clutch facing material and the counter material. The clutch facing material with the lower thermal conductivity and the fly-wheel material with the higher thermal conductivity showed the low and stable friction coefficient in the range of high sliding speed. This appears to be due to the formation of a film on the surface of the fly-wheel material.