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A custom-designed high-temperature sliding-on-sheet-strip (SOSS) tribo-tester was used to simulate the high-temperature friction process of 10Mn5 medium manganese steel bare plate under actual hot stamping conditions. To reveal its high-temperature friction mechanism in the hot forming process, the high-temperature friction behavior of 10Mn5 steel and 22MnB5 steel was compared. The scanning electron microscope (SEM), energy spectrum analyzer (EDS) and X-ray diffractometer (XRD) were used to investigate the structure of the oxide layer, composition of physical phase, wear surface morphology and elemental composition. The results show that the average coefficient of friction of 10Mn5 steel is 12.7% lower than that of 22MnB5 steel. The cross-section of both steel consists of an oxide layer, an alloying element-rich layer and the matrix. The oxide layer of 10Mn5 steel is mainly composed of Fe3O4, approximately 63.7%, while that of 22MnB5 is mainly composed of Fe2O3, approximately 66.9%. The complete and less flaking scale of 10Mn5 steel provides good wear protection, and the mechanism is abrasive with slight adhesive wear. Meanwhile, oxide particles and fragments are embedded in the 22MnB5 surface thus increasing the wear, and the mechanism evolves into severe abrasive and adhesive wear. The difference in the mechanism between the two steels is mainly caused by different austenitizing temperatures, which for 10Mn5 is lower than 22MnB5, about 100 °C. This makes the thermal stress of 10Mn5 from the temperature difference between the furnace and the environment not enough to break the scale and decrease abrasion. [ABSTRACT FROM AUTHOR]

A low-temperature Liquid Nitrogen Ring-on-Ring end-face contact friction Test Platform (LNR-RTP) was set up and applied to test the tribological behavior on metal/graphite ring-on-ring end-face contact pair. The friction coefficients and wear rates were obtained, and the wear mechanism was analyzed. The results show the friction coefficient increases with the rotational speed under the low temperature conditions and the low load from 50 to 100 N. With the load increasing, the friction coefficient is stable with the change of rotational speed, which is 0.05. The wear cross-section shows a taper shape from the inner to outer diameter, which implies a transition of the wear mechanism from the adhere wear to three-body wear under the low temperature conditions. [ABSTRACT FROM AUTHOR]

Hot stamping is an effective method to improve both the elongation and plasticity of ultra-high-strength steels and thus a higher specific strength can be achieved, making weight reduction in motor vehicles possible. However, due to the die temperature rise and the cooling liquid within hot stamping applications, the friction in its forming stage is always a nonisothermal mode. Therefore, a high-temperature slider-on–sheet strip (SOSS) tribotester to simulate sliding friction in hot stamping of 22MnB5 hot stamping steel sheet was designed and custom-made. Then, it was employed to exploit the high-temperature friction behavior and mechanism of bare 22MnB5 hot-stamped boron steel sheets under different die temperatures and extra cooling conditions. Results show that the friction coefficient obtained under the pure die cooling conditions is lower than that obtained under extra cooling conditions, which is attributed to the formation of thicker oxide layers on the surface of specimen during the cooling process. In addition, the friction coefficient is obviously decreased when the die temperature is increased to 200 °C, which is ascribed to the co-action of the destruction of the oxide layers and the formation of bainite. [ABSTRACT FROM AUTHOR]

The preparation methods of T300 carbon cloth- and aramid cloth-reinforced epoxy resin and cyanate ester were proposed, and four kinds of composite samples were obtained. The friction coefficient and wear rate under different test times and loads were obtained using a reciprocating pin-disk tribology tester. The tribology pairs included pins or sliding blocks made from different metals (45 steel and brass) and the disk samples of the composites. The test results showed that the friction coefficients of the T300 carbon cloth- (T300/4211 and T300/BS-4) and aramid cloth- (aramid/4211 and aramid/BS-4) reinforced epoxy resin or cyanate ester changed from 0.09 to 0.3 and were low under dry friction conditions. Under 75 N, aramid/BS-4 coupled with 45 steel pins was the lowest friction coefficient, which was 0.09. In particular, the friction coefficient and wear rate of the composite-reinforced cyanate ester were the lowest, which meant that this composite may be more suitable for use under lightly loaded and reciprocating running conditions in space engineering. By comparing the surface morphologies of composites before and after the test, the wear mechanism of the composites was discussed and the lower friction coefficient and wear rate may originate from the abrasive wear effects occurring between the tribology pairs. The research results have important engineering significance for guiding the use of composites in the deployable mechanisms used in space engineering. [ABSTRACT FROM AUTHOR]

Base oils containing different nanoparticles with varying concentrations are prepared, in which SiO2, TiO2 and ZnO (20 nm) nanoparticles are employed to improve the lubrication performance. Their tribological properties are evaluated on a ball-on-disk tribometer. The results show that the nano-additive lubricants exhibit a good friction reduction and anti-wear ability at the optimal concentration of 1.0 wt.%, in which SiO2 nanoparticles can reduce the coefficient of friction (COF) and the area of wear scar (AWS) by 45.6% and 35%, respectively. The SiO2 nanoparticles exhibit the best potential additive tested. The lubrication mechanisms of the nanoparticles can be attributed to the rolling, mending and the protective films. [ABSTRACT FROM AUTHOR]