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Polyimide-bearing retainer has been successfully used in space environment. However, the structural damage of polyimide induced by space irradiation limits its wide use. In order to further improve the atomic oxygen resistance of polyimide and comprehensively investigate the tribological mechanism of polyimide composites exposed in simulate space environment, 3-amino-polyhedral oligomeric silsesquioxane (NH2-POSS) was incorporated into a polyimide molecular chain and silica (SiO2) nanoparticles were in situ added into polyimide matrix and the combined effect of vacuum environment, and atomic oxygen (AO) on the tribological performance of polyimide was studied using bearing steel as the counterpart by a ball on disk tribometer. XPS analysis demonstrated the formation of protective layer induced by AO. The wear resistance of polyimide after modification was enhanced under AO attack. FIB-TEM confirmed that the inert protective layer of Si was formed on the counterpart during the sliding process. Mechanisms behind this are discussed based on the systematic characterization of worn surfaces of the samples and the tribofilms formed on the counterbody. [ABSTRACT FROM AUTHOR]

The wear resistance of 440C bearing steel balls significantly impacts the reliability of bearings. Our method for increasing the wear resistance of steel balls combines mechanical alloying to create nanogradient structures with ZrO 2 doping on the surface of the steel balls. The results revealed that ZrO 2 formed mechanical alloying on the surface of the steel balls. Under all loads, the processed samples exhibited excellent wear resistance. Compared to untreated samples, the wear of processed samples subjected to 20, 40, and 60 N loads decreased by 28.82 %, 50.25 %, and 50.79 %, respectively. The existing literature indicates that adding ZrO 2 powder during mechanical alloying is a promising method for improving the friction performance of bearing steel balls. • The processed sample had a maximum microhardness of 803.4 HV, while the untreated sample had increased by 22.13 %. • The micro pits, nano-gradient structure, and ZrO 2 all improved the wear resistance of steel balls. • The friction experiment revealed that the processed sample had a 50.79 % lower wear rate than the unprocessed 60 N load. [ABSTRACT FROM AUTHOR]

This study explored 440 C steel ball wear resistance via mechanical ball milling with Al 2 O 3 powder. We used a customized grinding jar to compare heat-treated, untreated, Al 2 O 3 -treated, and Al 2 O 3 + distilled water-treated samples. We assessed wear resistance, residual stress, microhardness, and surface roughness. Results revealed that the combination of distilled water and Al 2 O 3 powder induced nanostructured stacking faults, increased dislocation density, and grain refinement. Treated samples had a > 200 µm thick strengthened layer, − 355 MPa residual stress, and max microhardness of 776.6 HV. These samples showed superior wear resistance, reduced wear volume, and lower friction. This suggests that Al 2 O 3 powder and distilled water in mechanical ball milling enhance ball mechanical part wear resistance, offering industrial potential. [ABSTRACT FROM AUTHOR]

In this study, the wear resistance of AISI M2 high-speed tool steel produced using direct energy deposition (DED) was investigated in detail. Wear behavior was studied under different wear loads and sliding speeds using ball-on-disk tribology tests with two different counterpart balls (bearing steel and ZrO2). The wear test results revealed that there was almost no wear damage in the M2 alloy when a bearing steel counterpart ball was used. When a ZrO2 ball was used as the counterpart, a measurable, but small, amount of wear weight loss of M2 was observed. It was found that M2 alloy fabricated by DED has excellent wear resistance, greater than fully carburized conventional steel and high wear resistance steel produced by DED. The formation of a lubricious tribo-oxide film on the worn DED M2 surface is likely the reason for its excellent wear performance. The total wear weight losses of only ~1.5 mg was observed for the M2 produced by the DED, both in the as-DEDed and heat treated states against ZrO2 balls, under the wear loading conditions of 50 N wear load, 100 mm/s sliding speed and total sliding distance of 500 m. In comparison to the other wear-resistance materials, the wear weight loss of the M2 produced by the DED was more than 6 times smaller than the fully carburized structural steel and 1.5–4 times smaller than high wear resistance steel produced by the DED. Thus, DED of the M2 alloy offers a great potential for the production of wear-resistance hard-facing of tribological components. [ABSTRACT FROM AUTHOR]

Abstract: The tribological behavior of a Ni3Al alloy prepared by hot-pressed sintering was investigated at dry friction and sea water condition against AISI 52100 steel ball in ambient environment and at varying loads. The tribological results suggested that the Ni3Al alloy has the better wear resistance properties compared to Ti–6Al–4V alloy at dry friction and sea water conditions, and the Ni3Al alloy possesses the excellent wear resistance properties under sea water environment. Sea water plays a significant role in the improvement of tribological properties of the Ni3Al alloy, which has lubricating, cooling, and corrosive effects on the friction pairs. [Copyright &y& Elsevier]

Formulae are derived from first principles which predict the wear depth of a ball and a flat surface through time as they slide against each other, in relation to any phenomenological law for wear volume, and taking into account the effect of component geometry. The equations can be fit using experimental wear volume data from ball-on-flat tribometers. The formulae remove previous limiting approximations made in the literature and extend to the prediction of the wear depth of both contacting surfaces. The wear model accords with a previous model that is validated by pin-on-disc testing of a steel/steel contact. The current paper uses the formulae derived to predict the wear depth of a diamond-like carbon (DLC) coating and a steel ball as they slide against each other in deionised water. An Archard equation is used to predict the wear volume of each surface; however, a DLC coating is known to form a transfer layer which reduces the rate of wear, and since this scenario does not obey Archard's law directly, a time-dependent-specific wear rate is used to fit a semi-empirical model to experimental results. The final model predicts the wear depth of the ball and flat accurately. [ABSTRACT FROM AUTHOR]

This study aims to explore the wear performance of maraging 18Ni-300 steel, fabricated via laser powder bed fusion (LPBF). The building direction dependence of wear resistance was investigated with various wear loads and in terms of ball-on-disk wear tests. The effect of direct aging heat treatment, i.e., aging without solution heat treatment, on the wear performance was investigated by comparing the wear rates of directly aged samples, followed by solution heat treatment. The effect of counterpart material on the wear performance of the maraging steel was studied using two counterpart materials of bearing steel and ZrO2 balls. When the bearing steel ball was used as the counterpart material, both the as-built and heat-treated maraging steel produced by the LPBF showed pronounced building direction dependence on their wear performance when the applied wear load was sufficiently high. However, when the ZrO2 ball was used as the counterpart material, isotropic wear resistance was reported. The maraging steel produced by the LPBF demonstrated excellent wear resistance, particularly when it was aging heat-treated and the counterpart material was ZrO2. The directly aged sample showed wear performance almost the same as the sample solution heat-treated and then aged, indicating that direct aging can be used as an alternative post heat treatment for tribological applications of the maraging steels produced by LPBF. [ABSTRACT FROM AUTHOR]