• Tribology and Lubricants
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• v.33 no.6
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• pp.245-250
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• 2017

In this work, we examine pure water and water with nanoparticles to investigate water lubrication characteristics and the effect of nanoparticles as lubricant additives for different substrates. We test carbon-based coatings and metals such as high-speed steel and stainless steel in pure deionized (DI) water and DI water with nanoparticles. We investigate water lubrication characteristics and the effect of nanoparticles based on the friction coefficient and wear rate for different substrates. The investigation reveals that nanoparticles enhance the friction and wear properties of high-speed steel and stainless steel. The friction coefficient and wear rate of both high-speed steel and stainless steel decreases in DI water with nanoparticles compared with the results in pure DI water. The presence of nanoparticles in water show good lubricating effect at the contact area for both high-speed steel and stainless steel. However, for carbon-based coatings, nanoparticles do not improve friction and wear properties. Rather, the friction coefficient and wear rate increases with an increase in the concentration of nanoparticles in case of water lubrication. Because carbon-based coatings already have good tribological properties in a water environment, nanoparticles in water do not contribute toward improving the friction and wear properties of carbon-based coatings.

• Tribology and Lubricants
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• v.9 no.2
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• pp.49-55
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• 1993

The dry sliding wear properties of the sintered Cu-10 wt%Sn bronze alloys reinforced with $SiC_w$ and $SiC_p$ were investigated by a pin-on-disc wear testing machine. The worn surfaces and the cross sections of the wear specimens and the wear debris were observed by SEM to study the effect of the variation of the ceramic phase contents in the composite and the wear condition on the wear behaviors. The wear of bronze matrix was dominated by the adhesive wear. The transition from mild to severe wear was found in the bronze matrix specimens at the applied load higher than 20N where the surface delamination caused the severe wear. The addition of $SiC_w$ and $SiC_p$ reinforcements in the romposites was proved to reduce the wear rate by the matrix strengthening at the applied load higher than 20N. SiC whiskers having a large length to diameter ratio which hold the deformed matrix were effective to hinder the crack propagation near the worn surface. Thus the maximum wear resistance was obtained in the composite reinforced by $SiC_w$ at the higher applied load.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.1
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• pp.67-74
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• 2000

Recently, PTFE-polymide composites are being used self-lubricating parts for industrial field. Thus, this study is mainly concerned with friction and wear properties for the piston ring of non-lubricating air compressor which made of PTFE-polymide composites. The friction and wear test was carried out for the different composition ratio under the atomsphere room temperature and constant load of 7.69N and their friction and wear properties were compared with each other at various sliding speed. notable results are summarized as follows. PTFE 100% showed that friction coefficient was almost same values at 0.94 and 1.88m/s but the value was decreased at 2.83m/s because the friction temperature is higher than low speed. PTFE 80%-PI 20% showed the lowest mean friction coefficient at 2.83m/s. PTFE 20-PI 80% showed the highest friction coefficient at 0.94m/s and the value was decreased at high speed but the value is higher than other materials except PTFE 100 %. PI 100% showed the highest friction coefficient at 0.94 and 1.88m/s becuase adhesive wear mainly occurred that speed. PTFE 100% showed highest specific wear rate on the whole. Specific wear rate of PTFE 80%-PI 20% was almost the same value with PTFE 20%-PI80%. PI 100%showed the lowest value at high sliding speed because the friction surface was thicken and carbonated by high friction temperature.

• Tribology and Lubricants
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• v.24 no.2
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• pp.96-103
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• 2008

PTFE is generally utilized as the form of composites with adding various fillers. The purpose of this paper lies on clarifying the friction and wear properties of the PTFE coating layer on steel. Especially, the effects of PTFE powder size for coating and surface roughness of the counter material on the properties are investigated. Sliding friction and wear tests are conducted at several sliding speeds by employing two types of PTFE coating layer using different powder sizes. One type of coating layer is composed of uniform fine powder, whereas the other type is made up of mixture powder of different sizes. As results, it is found that PTFE coating layer are effective to improve the wear resistance and to reduce the friction coefficient. It is clear that PTFE coating layers are abrasively removed by asperities of the counter material during sliding contact. However, PTFE coating layer with uniform fine powder shows somewhat better wear resistance than that with mixture powder of different sizes in low sliding speed region. It can be seen that the wear of the coating layer are drastically reduced because wear fragment from counter material are transferred to the coating layer. On the other hand, friction coefficient is shown not to be directly related with PTFE powder size in coating layer.

• Korean Journal of Metals and Materials
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• v.48 no.11
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• pp.1003-1008
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• 2010

In this study, the effect of the reinforcement on the wear behaviour and mechanical properties of hypereutectic Al-Si alloys was investigated. The Gas atomized hypereutectic Al-20Si alloy powders were mixed with 1, 3, and 5 wt.% AlN and TiC ceramic particles and consolidated by hotpress. The Al-20Si powder has both finely dispersed primary Si phases and eutectic structures. The Al-20Si-AlN, TiC composites showed that the reinforcements were distributed along the boundary of the Al-20Si alloy. The UTS increased with increasing the AlN, TiC contents. At a lower load, with an increasing weight fraction of reinforcements, the wear rate decreased in both composites and the wear mechanism was adhesive wear. At a higher load, the shape of the debris changes the mechanism of the AlN composites to abrasive-adhesion wear and this resulted in an increase of the wear rate.

• Tribology and Lubricants
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• v.13 no.1
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• pp.21-27
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• 1997

The friction and wear behavior of undulated surfaces made of tin base babbit are examined experimentally at the low sliding speed with severe loading condition. Steel is used as counterface disk material under pin-on-disk type sliding condition. Undulated surfaces can improve the friction and wear properties under dry friction condition since undulated surfaces trap wear particles in their cavities and prohibit wear particles from agglomerating. However, under boundary lubrication condition, friction and wear properties of undulated surfaces are inferior to those of flat surfaces. It is shown that land width and the ratio of wear volume to cavity volume are the most important factors in friction behavior of undulated surfaces under dry friction condition, and there exists optimum land width minimizing friction and wear of undulated surfaces.

• Tribology and Lubricants
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• v.10 no.3
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• pp.39-46
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• 1994

In order to investigate the effect of the ceramic reinforcements on the wear properties of aluminum bronze composites, Cu-8wt%Al aluminum bronze alloys reinforced with the Saffil alumina short fiber were produced by the powder metallurgical method and tested by a pin-ondisc wear testing machine. The wear surfaces of the pin specimens and discs, wear debris, and the cross sections of the wear specimens were observed by SEM. The wear mechanism according to various wear conditions and the change of microstructure in the composites were also discussed. In the results, the reinforcement of the composites with alumina short fiber was very effective at the higher applied load over 10N. The material transportation to the counter disc was observed in the alloy specimens without reinforcements. However, the composites reinforced with ceramic particles and fibers showed the resistance against the material transportation.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.115-121
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• 2001

The wear test has been performed to evaluate the wear mechanism of steam generator (SG) tube materials against ferritic stainless steel in water environment. The wear rates of SG tube materials depend on the change of mechanical properties between contact surfaces during wear test. From the subsurface hardness test, Inconel 690 is more work-hardened than Inconel 600 even though these materials have similar hardness values before the wear test. Main cause is due to the difference of stacking fault energy with the chromium content. In water environment, wear mechanism is closely related with the continuous formation and fracture of deformation layers at the contact surfaces.

• Geomechanics and Engineering
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• v.35 no.6
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• pp.647-663
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• 2023

The investigation of the disc cutter wear prediction has an important guiding role in TBM equipment selection, project planning, and cost forecasting, especially when tunneling in a long-distance rock formations with high strength and high abrasivity. In this study, a comprehensive database of disc cutter wear data, geological properties, and tunneling parameters is obtained from a 1326 m excavated metro tunnel project in leptynite in Shenzhen, China. The failure forms and wear consumption of disc cutters on site are analyzed with emphasis. The results showed that 81% of disc cutters fail due to uniform wear, and other cutters are replaced owing to abnormal wear, especially flat wear of the cutter rings. In addition, it is found that there is a reasonable direct proportional relationship between the uniform wear rate (WR) and the installation radius (R), and the coefficient depends on geological characteristics and tunneling parameters. Thus, a preliminary prediction formula of the uniform wear rate, based on the installation radius of the cutterhead, was established. The correlation between some important geological properties (K_V and UCS) along with some tunneling parameters (F_n and p) and wear rate was discussed using regression analysis methods, and several prediction models for uniform wear rate were developed. Compared with a single variable, the multivariable model shows better prediction ability, and 89% of WR can be accurately estimated. The prediction model has reliability and provides a practical tool for wear prediction of disc cutter under similar hard rock projects with similar geological conditions.

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.1069-1075
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• 1994

When ceramics are used as the parts of an engine and a machine, the tribological properties are very important. For the preparation of the resistance material for wear applications by the method of Reaction-Bonded Sintering, metal silicon and carbon black are mixed up into SiC powder, and Al2O3 and Fe2O3 are put as an additive. As the general properties, the bending strength and water absortion are measured in the normal temperature and the phase changies are investigated with XRD. The property of the resistance for wear applications is measured with the amount of friction and wear, friction coefficient and maximum asperties. And, the surface of wear is observed with SEM. With the results of this study, the optimal mol ratio of Si : C and the suitable quantity of the mixture of SiC are 7 : 3 and 40 wt%, respectively. In the case of the addition of Al2O3 (2 wt%), the resistance for friction and wear applications is prominent. The bending strength showed the highest peak when Al2O3 (4 wt%) and Fe2O3 (4 wt%) were added. The properties of friction and wear were related with the propagation velocity of crack rather than the bending strength.