• Tribology and Lubricants
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• v.34 no.6
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• pp.284-291
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• 2018

Ball-milling for reactant powders in advance and using an induction heating system for Ni-Al intermetallic coating process are known to enhance the reactivity of combustion synthesis. In this work, the effects of the charging weight ratio of ball to powder in ball-milling for reactant Ni-Al powders and the synthesizing temperature in induction heating on sliding wear behavior of the coating layers are investigated. Sliding wear behavior of the coating layers is examined against a tool steel using a pin-on-disc type sliding wear machine. As results, wear of the coating layer ball-milled without ball was severely worn out at the sliding speed of 2m/s, regardless of the synthesizing temperature in induction heating. However, the wear rate of the coating layers at the sliding speed was remarkably decreased with increasing the charging weight ratio of ball in ball-milling for reactant powders. This can be explained by the fact that the void in the coating layer is disappeared and the coating layer is densified by the ball-milling. The evidence showed that pitting damages were disappeared on the worn surface of ball-milled coating layer. Consequentially, the Ni-Al intermetallic coating layer could have better wear resistance at all sliding speed ranges with the ball-milling for reactant powders in advance.

• Tribology and Lubricants
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• v.16 no.5
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• pp.324-331
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• 2000

Wear characteristics of Plastic and Nylon pinions against steel gear were studied to gain a better understanding of their tribological behaviors. Wear tests were conducted with power circulating gear test rig under dry contact conditions. Specific wear rates were measured as a function of applied load and the number of revolution. The worn teeth surfaces were examined with a profile projector and a camera. Nylon pinion showed lower specific wear rates than acetal pinion, but suffered teeth breakage under high load per unit tooth width. The dominant wear mechanisms found were adhesion and abrasion.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.148-153
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• 2007

The effect of silicon carbide (SiC) and graphite fillers incorporation on the abrasive wear behaviour of glass-vinyl ester (G-V) composites have been investigated. The three-body abrasive wear behaviour was assessed by rubber wheel abrasion tests (RWAT). The worn surfaces were examined using scanning electron microscopy (SEM). The addition of SiC and graphite fillers in G-V composite improves the abrasion resistance under different loads/abrading distances. The SEM studies indicate the reasons for failure of composites and influencing parameters.

• Tribology and Lubricants
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• v.21 no.6
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• pp.302-305
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• 2005

Various carbon nanotubes (CNTs) are added into the epoxy matrix as reinforcements to investigate the effect on the wear behavior. Effects to the tribological properties of different loading concentrations and types of surface modification are investigated by using a linear reciprocal wear tester. As increasing the concentration of CNTs shows the reduction of the wear loss. Moreover, surface modified CNTs give better tribological property than as produced CNTs. It is due that the functional groups on the surface of CNTs increase the interfacial bonding between CNTs and epoxy matrix through chemical bonding. Changes in worn surface morphology are observed by optical microscope and SEM to investigate the wear behavior. CNTs in the epoxy matrix near the surface are exposed and it becomes the lubricating working film on the worn surface. It reduces the friction and results in the lower surface roughness morphology in the epoxy matrix as increasing the contents of the CNTs.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.17-24
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• 1998

Plasma-sprayed coatings were obtained by spray-dried $Cr_2O_3$ powder with and without Mo addition. A reciprocal type tribo-tester was employed to examine friction and wear behavior of the specimens at room temperature. The composition and the worn surface of coated specimens were observed by XRD and SEM. The results showed that friction Coefficient of the Mo added specimens were lower than one of $Cr_2O_3$ specimen. But $Cr_2O_3$ specimen had a lower wear loss. Protecting layer were observed at the worn surface of coated specimens with Mo addition.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.22-29
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• 2001

Plasma-sprayed coatings were prepared using by spray-dried Cr$_2$O$_3$ powder with and without MoO$_3$ addition. A reciprocal type tribe-tester was employed to examine friction and wear behavior of the specimens at room temperature. The worn surfaces of plasma spray coated specimens were observed by SEM. The results showed that friction coefficient of the MoO$_3$-added coatings were lower than those without MoO3 addition. However pure Cr$_2$O$_3$ coating showed the lowest wear loss at the self-mated test. The larger protecting layers were observed at the worn surface of plasma spray coated specimens with MoO$_3$ addition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1091-1098
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• 2009

In this paper, the procedure to estimate fatigue crack initiation life has been established by considering fretting wear and multiaxial stress states on the contact surface of press-fitted shafts. And a method to calculate the local friction coefficient during the running-in period of fretting wear process has been proposed. The predicted result of worn surface profile in the press-fitted shaft with non-linear local friction coefficient can avoid excessive wear depth estimation compared with that for the case of constant local friction coefficient. Furthermore, the predicted fatigue crack initiation lives based on Smith-Watson-Topper model considering the fretting wear are in good agreement with the experimental data. Consequently, the present method is valid not only for predicting worn surface profile, but also for assessing fatigue crack initiation lives considering the fretting wear during the running-in period in press fits.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.147-150
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• 2001

The ARB (Accumulative Rolling Bonding) Process was applied to a 6061 Al alloy to obtain ultra-fine grains. After 4 ARB cycles at $315^{\circ}C$, original equilibrium large grains were transformed to ultra-fine grains of several hundred nano-meter size with nonequilibrium grain boundaries. At lower number of cycles, microsutcture of highly-tangled dislocation cells were observed. Large grains and coarsened precipitates filled the microstructure of specimens experienced ARB cycles more than 5. Sliding wear tests using a pin-on-disk type wear tester were conducted on the ARB processed 6061 Al alloy plate. Wear rates of the 6061 Al alloy increased with the increase of ARB cycle number as well as the applied load. Worn surfaces and debris, cross-sections of the worn specimen were examined with scanning electron microscopy (SEM) to investigate the wear mechanism of the ultra-fine grained 6061 Al Tensile properties of the 6061 Al alloy were also studied and used to correlate the wear test results with the microstructures, which evolved continuously with the number of ARB cycles.

• Tribology and Lubricants
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• v.16 no.4
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• pp.282-288
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• 2000

A sliding friction and wear test for silicon nitride (Si,N4) was conducted using a ball-on-disk specimen configuration. The material used in this study was HIPed silicon nitride. The tests were carried out from room temperature to 1000$^{\circ}C$ using self-mated silicon nitride couples in laboratory air. The worn surfaces were observed by SEM and the debris particles from the worn surfaces were analyzed for oxidation by XPS. The normal load was found to have a more significant influence on the friction coefficient of the silicon nitride than an elevated temperature. The specific wear rate was found to decrease along with the sliding distance. The specific wear rate at 29.4 N and 1000$^{\circ}C$ was 292 times larger than that at room temperature. The main wear mechanism from room temperature to 750$^{\circ}C$ was caused by brittle fracture whereas from 750$^{\circ}C$ to 1000$^{\circ}C$ the wear mechanism was mainly influenced by the oxidation of silicon nitride due to the increased temperature. The oxidation of silicon nitride at a high temperature was a significant factor in the wear increase.

• Proceedings of the KWS Conference
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• 2001.05a
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• pp.245-247
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• 2001

In this study, the effects of dilution on the wear behavior of PTAW (Plasma Transferred Arc Welding) Inconel 625, Inconel 718 and Stellite 6 overlays on Nimonic 80A were investigated. Inorder to evaluate the wear performance, two-body and three-body abrasive wear test, and dry sliding wear test were performed. According to wear tests, the wear rate of deposit with dilution 30% was higher than that of dilution 10% by 10%, and it was also found the plastic deformation near worn surface.