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• Polycrystalline Mo 2 BC ceramic bulks were successfully prepared from elemental powders by SPS route. • The synthesized temperature of Mo 2 BC ceramic was confirmed to be as low as 1300 ºC. • The lattice parameters of as-prepared Mo 2 BC ceramic were determined by TEM characterization. • For the first time, the mechanical properties of Mo 2 BC ceramic bulks were investigated. Single-phase polycrystalline Mo 2 BC ceramic bulks were synthesized successfully from molybdenum, boron, and graphite powders using the spark plasma sintering method. Herein, it was established that the synthesis temperature of the Mo 2 BC ceramic could be as low as 1300 °C. Transmission electron microscopy (TEM) characterization confirmed that the crystal structure of the Mo 2 BC ceramic was comparable to that of the MoAlB ceramic. The Vickers hardness of the Mo 2 BC ceramic was measured to be 18.1 GPa. Additionally, the compressive strength, flexural strength, and fracture toughness were determined to be 1.74 GPa, 457.72 MPa, and 3.26 MPa· m1/2, respectively. The Mo 2 BC bulk exhibited typical brittle features, in which intergranular and transgranular fractures were the main failure modes. [ABSTRACT FROM AUTHOR]

Herein, in situ MoB particles reinforced Cu-Al matrix composites are prepared by sintering the Cu and MoAlB mixture. During the sintering process, Al atoms can diffuse out of the layered MoAlB and solid-dissolve into the Cu matrix, resulting in the formation of laminate MoB and Cu-Al alloy. The mechanical properties of as-prepared composites are significantly improved because of multiple strengthening mechanisms. Moreover, the two-body abrasive and adhesive wear effects are inhibited on account of the pinning effect of MoB particles. With the MoAlB content increasing up to 20 wt% and 30 wt%, a layer of tribo-film can be generated due to the tribo-oxidation reaction during the sliding, which can provide lubrication to reduce friction and wear. • In-situ MoB reinforced Cu-Al matrix composites are prepared for the first time. • The mechanical and tribological properties of as-prepared composites are improved. • Two-body abrasion and adhesive wear can be inhibited with MoAlB addition. • The generating tribo-film leads to the low friction coefficient and wear rate. [ABSTRACT FROM AUTHOR]

In this paper, a series of calcium borate/graphene oxide (CB/GO) composites were synthesized using borax, calcium nitrate and graphene oxide by hydrothermal method. The composites were characterized by means of Fourier transform-infrared spectroscopy (FT-IR), Raman, transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The friction and wear properties of oleic acid (OA) modified CB/GO composites were also investigated using four-ball wear tester. Our results showed that the friction and wear properties were improved by forming an interfacial boundary lubrication layer. [ABSTRACT FROM AUTHOR]

In this study, Mo 0.9 Cr 0.1 AlB solid solution ceramic bulks were prepared from the element powder mixtures using hot pressing sintering method. Compared with MoAlB ceramics, the grains of as-prepared Mo 0.9 Cr 0.1 AlB were refined obviously. The lattice constants of Mo 0.9 Cr 0.1 AlB were confirmed to be a = 3.205 Å, b = 13.999 Å and c = 3.098 Å. The density of Mo 0.9 Cr 0.1 AlB was lower than that of MoAlB due to the incorporation of Cr element. In addition, the effect of doping Cr element on the comprehensive mechanical properties was studied as well. The hardness and compressive strength were improved significantly. In comparison with MoAlB ceramic, the improvement of mechanical properties could be attributed to solid solution strengthening and grain refinement. [ABSTRACT FROM AUTHOR]

Electrical erosion pit is a fundamental manifestation of electrical bearing damage. As the shaft voltage increased, the degree of electrical damage became more severe, and the residual compressive stress and hardness of bearing surface decreased. The transition of martensite into ferrite induced by high discharge temperature was found at the edge of the erosion pit using a transmission electron microscopy. This phenomenon has not been observed below the mechanically rolled surface under the same conditions. Electrical penetration harmed the bearing through surface erosion, lubrication deterioration and martensite decomposition. The electrical pit could be observed when current density exceeded 0.95 A/mm2. The results can help understand bearing failure in the fields of railways, wind turbines, and new-energy vehicles. • Transformation of martensite into ferrite have been observed around erosion pit. • Segregation of carbides at subsurface was the results of martensitic decomposition. • Residual stress and hardness decreased in the erosion surface. [ABSTRACT FROM AUTHOR]

As lubricant additive, graphene and/or graphene oxide (GO) has received considerable interest due to its excellent tribological performance. Here, grafting octadecylamine(ODA) onto GO via facile amidation was carried out and hydrazine monohydrate was used as reducing agent to attain ODA-RGO as lubricant additive. The physical, chemical properties and morphologies of ODA-RGO and GO were characterized.Tribological properties were evaluated using a ball-on-plate configuration on a UMT-3 tribometer and then worn surfaces were examined by Scanning electron microscope (SEM), Raman spectra and optical microscope. It was found that ODA-RGO was helpful for lubrication and friction-reduction under the applied load of 10 N. The excellent tribological behavior was contributed to the formation of ODA-RGO protective film which could avoid direct contact between tribological mates. The restacked shape of sheet-like ODA-RGO also plays an important role in friction process. • ODA-RGO was synthesized as lubricant additive. • ODA-RGO shows excellent tribological behavior. • Restacked ODA-RGO with flake structure might play an important role in protecting sliding mates. [ABSTRACT FROM AUTHOR]

Abstract: The friction and wear properties of synthetic ionic liquid functionalized borate esters as additives in poly-alpha-olefin (PAO) were measured for diamond-like carbon (DLC) coating on plasma nitrided AISI 1045 steel. Results show that the borate esters gave much better friction–reduction and antiwear properties for DLC coating/steel and DLC coating/DLC coating sliding pairs than zinc dialkyldithiophosphate (ZDDP). In addition the DLC coating had much better wear resistance than the nitrided mild steel substrate, indicating that duplicate surface modification was more effective in significantly increasing the wear resistance of mild steel. [Copyright &y& Elsevier]

In this study, the tribological behaviors of Mo 2 BC ceramics against four different counterpart materials were studied. It was established that the tribological properties of Mo 2 BC were sensitive to the counterpart material. For the Mo 2 BC/SiC and Mo 2 BC/Al 2 O 3 tribo-pairs, a layer of tribofilm, mainly consisting of MoO 3 , was generated owing to the tribo-oxidation reaction. However, the tribofilm did not provide lubrication under ambient conditions. Tribo-oxidation and adhesion wear were the main wear mechanisms. For the Mo 2 BC/Si 3 N 4 tribo-pair, only minor MoO 3 tribo-oxides were generated, and the tribo-pair showed better tribological properties; the friction coefficient was as low as 0.42. The dominant wear mechanism was two-body abrasion. The Mo 2 BC/GCr15 steel tribo-pair showed a high friction coefficient, owing to the adhesion effect of Fe. • The tribological behaviors of Mo 2 BC ceramic are sensitive to the counterpart materials. • The tribo-film containing MoO 3 cannot provide lubricity at room temperature. • Tribo-oxidation wear causes high wear rate of Mo 2 BC. [ABSTRACT FROM AUTHOR]