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Copper-based sintered composites produced by powder metallurgy processes are now widely used in tribological engineering parts, e.g. bearings and bushes. Also composites based on copper-tin alloys containing a solid lubricant have been developed as self-lubricating materials under extreme conditions of load, atmosphere and temperature. It is well known that the addition of graphite serves to reduce...
Mechanical face seal performance is critically dependant on the tribology of the seal face materials. In this research the tribology of the premier seal face materials under dry running contact has been examined. It is shown that the PV (pressure×velocity) capability, of these premier face materials, is dependant on the development of a carbon graphite contact film. Experimentation has shown that...
Ball-against-disk type fretting wear tests for Al-Si alloy matrix composites in contact with bearing steel were conducted in wet air to investigate the effects of relative slip amplitude on friction and wear of the composites. In the larger range of relative slip amplitude, the Al-Si alloy-impregnated graphite composite (ALGR-MMC) shows lower friction coefficients than those of alumina short fiber-reinforced...
In order to overcome the shortcomings of present switch slide baseplates, a kind of epoxy composite was designed as lubricating coatings for switch slide baseplates. The wear tests of epoxy composite specimens paired with A36 steel specimens under air-lubricated condition were carried out on a ring-block wear tester typed M200. After the wear tests, the worn surfaces of steel specimens were examined...
The influence of vapour-grown carbon nanofibres (CNF), of average diameter 150nm, on the wear behaviour of semicrystalline poly(ether ether ketone) (PEEK) was investigated. Unidirectional sliding tests against two different counterpart materials (100Cr6 martensitic bearing steel, and X5CrNi18-10 austenitic stainless steel) were performed on injection moulded PEEK-CNF nanocomposites. The specific wear...
The Al–Si alloy impregnated graphite composite containing a high content (56vol.%) of graphite has a good self-lubricating performance in moist air under dry sliding. In this paper, pin-on-disk type wear tests of the composite in contact with bearing steel were conducted in various gas environments to investigate the wear mechanism under dry sliding. The composite exhibits a decrease in wear at high...
The comparative performance of glass–epoxy (G–E) composites, having rubber in one instance and graphite of two differing levels in epoxy matrix resin in the other, during sliding in pin-on-disc type set up under varying load and sliding velocities is reported in this investigation. Besides conventional weighing, determination of coefficient of friction (μ) and examination of the worn surface features...
Wear particles often agglomerate into cohesive transfer films (so-called 3rd body) during dry friction. Although described in terms of load carrying capacity and velocity accommodation, the 3rd body finally became a kind of black box where the comprehension of the real interactions, which occur in the tribocontact, can be unknown. We study the behaviour and the mechanisms of action of the 3rd body...
In this paper we present experimental and analytical techniques for identifying the coefficient of friction (COF) of a graphite electric brush sliding against a commutator for different contact temperatures and electric current densities. A direct measurement of the instantaneous dynamic forces is used to identify the coefficient of friction. The experimental example shows that the presented procedures...
The multiple parts of this study are intended to experimentally and analytically elaborate the tribological properties of epoxy nanocomposites, reinforced by short carbon fibres (SCF), nano-TiO 2 particles, polytetrafluorethylen (PTFE) powders and graphite flakes, in order to understand the role of fillers in modifying the wear behaviour of the materials. In this part, the influences of two...
Wear particles are produced as a result of interaction of two surfaces in mechanical systems. After extracting and separating particles by different techniques (filtration, ferrography …), their morphology, which is a function of the condition of tribological system (tribosystem), can be related directly to the wear process. In order to understand wear mechanisms, it is interesting to study the relationship...
Graphite modified polyester–cotton composites were developed and studied for friction and sliding wear behaviour at different applied loads and graphite concentrations. Sliding wear tests were conducted using pin-on-disc apparatus. The composite pins were tested against EN-31 steel disc. The specific wear rate of polyester reduced on reinforcement of cotton and on addition of graphite. The coefficient...
The aim of this study is to present the fretting tribological behaviour of stainless steel/graphite and stainless steel/carbon impregnated with silver couples in a dry shaft/bearing contact with thrust. Two contact geometries are investigated: cylinder-in-cylinder and plan/plan. Both of them are subjected to low-amplitude (20 to 250μm) oscillatory movements, with temperature reaching 270°C. The morphological...
Tribological behaviour of Al/Saffil/C hybrid composites with various amounts of graphite and alumina fibres, produced by the squeeze casting method, was studied. Preforms with about 6.5–15.0% (all the percentages v/v) of Al 2 O 3 fibres (Saffil) and 1.5–12.0% of graphite were infiltrated under the pressure of 75MPa. The effects of the applied load, form of graphite, and the reinforcement...
Decoupled graphite lubrication of monolithic silver brushes on a copper rotor was studied in an ambient air environment under current varying from 0A/cm 2 to 200A/cm 2 using a custom designed electrical contact tribometer. Bifurcation of the positive and negative brush wear rates was observed at a current density of 200A/cm 2 . Energy dispersive spectroscopy showed transfer...
In metallic contacts, surface oxides, adhesion, and material transfer play a primary role in the initial stages of fretting wear degradation. Given this behavior, the focus of this study was to mitigate fretting wear within Ti6Al4V contacts at room temperature and 450°C with the use of thermally sprayed nickel graphite composite coatings with 5–20% graphite. The results show that the embedded graphite...
Copper–carbon composites with pitch coke as reinforcement and the graphite/pitch coke ratio of 10/90, 30/70, 50/50, 70/30 and 90/10wt% were prepared using compression molding and sintering method. The bending strength and micro-hardness of the composites were measured by a universal tester and Vickers hardness tester, respectively. The friction and wear behaviors of the composites were evaluated using...
The sliding performance of PEEK composites was investigated in vacuum environment. Tests were performed with carbon fibre reinforced PEEK composites filled with PTFE, and MoS 2 or graphite as further solid lubricant. Polymer samples were tested in a pin-on-disc configuration continuously sliding against CrNi-steel. Depending on sliding speed and temperature, the MoS 2 filled composites...
In this study, the frictional and wear characteristics of sintered copper matrix composite brake pads against cast Al–Si/SiCp brake disc and the effects of applied load on the coefficient of friction have been reported. Tribological behavior of Cu-MMC/Al-MMC couple was studied using Pin-on-Disc tribometer. The aluminum metal matrix composite material was used as a disc, whereas the graphite reinforced...
A cross-section sample of the friction film formed on top of a disc during a brake testing procedure against Polymer Matrix Composite pads was made using a Focused Ion Beam (FIB). The FIB-cut sampled the “third body” magnetite layer and the upper part of the cast iron disc containing a graphite flake. Images of the sample examined in a Energy Filtered Transmission Electron Microscope captured an instant...
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