Papers by Keyword: Tribological Behavior

Abstract: The performance and reliability of sliding bearings are strongly influenced by the tribological properties of the materials employed. In the present study, the wear behavior of a bronze alloy was investigated under lubricated conditions using SAE 20W-40 engine oil as the working fluid. To enhance performance, a bronze–Cr–Ag alloy system was developed and its tribological response was evaluated against AISI 52100 bearing steel under controlled laboratory conditions. The study focused on key parameters such as the coefficient of friction, wear rate, and material loss, which are critical in determining the operational life of bearings. Furthermore, the role of lubricants in mitigating tribocorrosion was examined, highlighting how SAE 20W-40 oil interacts with the alloy surface to form protective films, thereby minimizing direct metal-to-metal contact. The findings demonstrate that bronze-based alloys, when modified with chromium and silver, exhibit superior tribological performance in lubricated environments, making them promising candidates for sliding bearing applications.

Abstract: The tribological behavior of Ti_49.4Ni_50.6, Ti₄₉Ni₄₆Cu₅ and Ti₅₀Ni₄₇Co₃ (at%) alloy in dry and wet conditions was studied. The alloy was prepared in a Vacuum Arc Re-melting (VAR), homogenized at 800°C for 3600 s and quenched in water. The phase transformation temperatures were measured by differential scanning calorimetry. Before a tribology test, it is necessary to determine surface roughness, because high surface roughness affects friction. The hardness behavior, based on the load over residual indent area, was determined by a Vickers hardness tester. The sliding friction tests were performed using a ball-on-disk tribometer in dry condition at room temperature and wet condition in artificial saliva (pH 5.35) at 37°C (Oral temperature). The results showed that transformation temperature (Af) lowered oral temperature (37°C), this was mainly attributed to the superelastic properties that can be taken into orthodontic applications. The studies showed significant influences in dry condition of coefficient of friction. Caused by the force between the ball and the disk, contact pressure of surface area effect in wear occurred. The debris could not be removed from the surface area tested. TiNiCu and TiNiCo generated significantly lower average coefficient of friction when tested under dry condition, which may have been due to the addition of Cu and Co. Wet condition decreased coefficient of friction more than dry condition, owing to the lubricating effects of artificial saliva.

Abstract: The chemical compositions and microstructures of several different cemented carbides were checked by XRD, XRF, SEM, metallographic microscope and stereomicroscope. The influences of phase compositions and microstructures on mechanical properties were investigated. The results show that improving the Co content and refining WC grain properly are effective means to acquire the excellent mechanical properties of cemented carbide. A series of friction and wear tests were carried out in a high-speed tribometer to explore the tribological behavior of three cemented carbides with different Co content and WC grain size against aluminum alloy 7050-T7451. It was found that the tribological behaviors of cemented carbides are largely dependent on their microstructures and mechanical properties. The enhancement of flexural strength and fracture toughness can be ascribed to deformation buffering effects of Co binder, but the improved hardness depends on the rigid skeleton of WC-WC grains.

Abstract: In this investigation, micro crystalline diamond (MCD) and nanocrystalline diamond (NCD) films are deposited on cemented carbide (WC-Co) balls by hot filament chemical vapor deposition (HFCVD) technique. After deposition, MCD and NCD films are characterized by field emission scanning electron microscopy (FESEM) and Raman spectroscopy. Then frictional tests are carried out between CVD diamond coated balls and graphite. The results show that the MCD-graphite and NCD-graphite tribo-pairs exhibit comparable frictional coefficients, while the wear rate of graphite in MCD-graphite working pair is much higher than that of graphite in NCD-graphite working pair. Furthermore, the element oxygen is detected in the wear groove of graphite, suggesting the oxycarbide of working materials at the increased temperature due to the heat generated from the mechanical friction.

Abstract: New iron-based composite materials with addition of barium carbonate (2 to 8 wt% barium carbonate) for friction applications are investigated. The tribological behavior of the studied materials was determined by a pin-on-disk method when a cast iron disk was employed. The addition of 2 wt% barium carbonate determined a significant increase of the average friction coefficient. Instead a further increase of barium carbonate content determined a gradual decrease of this parameter. The improvement of wear resistance was marked out for a barium carbonate content of up to 6 wt%. The optimal ratio between the average friction coefficient and the wear rate for the researched Fe-Cu-graphite-Ni-BaCO₃ composites was determined for the iron-based material containing 2 wt% barium carbonate. SEM, EDX and XRD analysis marked out a complex structure containing alloyed ferrite, pearlite and carbides, traces of nickel and barium carbonate and free graphite.

Abstract: PAI/SiC-and PAI/SiC/PTFE-composite coatings were prepared, which were deposited on Al substrates using spraying technology to improve their surfaces performance. Friction and wear of PAI composite coatings were evaluated on a ball-on-block wear tester, and thermal properties were investigated by TG. It is found that, the friction coefficient and wear rate of PAI coatings reaches the best value when the content of SiC and PTFE is 10 wt % and 0.8wt% respectively, and the friction coefficient of the composites coatings decrease but the wear rate increase with increasing applied load; TG curves shows that the PAI composite coatings have excellent heat resistance. Furthermore, the surface of PAI coatings is perfect without bubbling, desquamating and cracking when it is heated for 2 hour at 250^◦C in turn three cycles.

Abstract: Three novel B, N, S-containing tri(hydroxymethyl) propane (TMP) esters with different alkyl chains were synthesized and characterized. Thermal degradation tests were performed to analyze their thermal stability using a thermo-gravimetric analyzer. The friction-reducing performance of the synthesized compounds as additives in rapeseed oil (RO) was evaluated with a four-ball tester. The results show that the novel B, N, S-containing TMP esters have excellent thermal stability and possess good friction-reducing behavior when they are used as additives in rapeseed oil.

Abstract: Three novel B, N, S-containing tri (hydroxymethyl) propane (TMP) esters were synthesized. The anti-wear performance of the synthesized compounds as additives in rapeseed oil (RO) was evaluated with a four-ball tester. The results show that the novel TMP esters have good antiwear performance when they are used as additives in rapeseed oil under all test loads. The action mechanism was investigated through analysis of the X-ray photoelectron energy spectrometer. The results indicate that the additives in RO adsorb and react with metal surface to form a protective film composed of organic compounds, B₂O₃ and iron oxide.

Abstract: A new type of interpenetrating phase composites (IPC) was prepared by impregnating open-cell aluminum foam (AF) with polyoxymethylene (POM) through an injection molding process, and their mechanical properties has been investigated. It shows relatively high bending strength and impact strength with compared to the pure AF and POM. With the addition of 10wt% polytetrafluoroethylene (PTFE) to POM, the mechanical properties of the IPC are further improved . On the other hand, Tribological tests of IPC were carried out with a pin-disk machine, and their worn surfaces were characterized by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) to explore the wear mechanism. Results show that the friction coefficient of AF/POM/PTFE IPC is about 12.7% lower than that of AF/POM IPC and the wear loss reduced by 33.3%. The reason of the increase in the wear resistance can be explained by the transfer film which delays the wear process.

Abstract: The tribo-map of typical CVD diamond film exhibiting the interaction between the wear rate, friction coefficient and friction conditions would help optimize the working parameters of CVD diamond film coated tools and wear-resistance components. The tribological behaviors of CVD diamond films sliding against Si₃N₄ balls were studied by conducting a group of tests on the ball-on-plate type reciprocating friction tester under several sliding speeds and normal loads in the ambient air. The examined MCD films and NCD films were deposited on square flat WC-Co substrates. The worn surfaces on the diamond films were observed by SEM and the wear volumes of diamond films were measured by surface profilometer. The results indicated that the influences of the sliding speeds and normal loads on the friction coefficients for both MCD films and NCD films were obvious. When the load was 6 N, MCD film obtained the lowest friction coefficient of 0.11 at the sliding velocity of 0.2 m/s, while for NCD film the minimum value was 0.07 as the sliding speed was 0.13 m/s. The wear rate of the MCD film decreased as the load improved, while for the NCD film, the tendency was just the opposite. The influence of sliding speed on the wear rate of the MCD films was not distinct, while for the NCD films, the sliding velocity greatly affects their wear rate. The wear rates of most NCD films were around 0.2×10^-7 mm³/Nm, while those of the MCD films fluctuated from 0.6×10^-7~1.6×10^-7 mm³/Nm. To elucidate the effect of operating environment on wear mechanism of diamond/ Si₃N₄ tribo-pair, the tribo-map was developed.