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Abstract: The tribological properties of Ni-17.5Si-29.3Cr alloy against Si3N4 were studied on a ball-on-disc tribotester between room temperature and 1000°C. The effects of temperature on the tribological properties of the alloy were investigated. The worn surfaces of the alloy were examined using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results indicated that the tribological behavior of the alloy expressed some differences with increase in testing temperature. At low and moderate temperatures (below 800°C), the alloy showed excellent wear and oxidation resistances, and the wear rate of the alloy remained in the magnitude of 10−5 mm3/Nm; but at elevated temperature (800–1000°C), the wear and oxidation resistances decreased, and the wear rate of the alloy increased up to 10−4 mm3/Nm. The friction coefficient decreased from 0.58 to 0.46 with the rising of testing temperature from 20 to 600°C, and then remained nearly constant. The wear mechanism of the alloy was mainly fracture and delamination at low and moderate temperatures, and transformed to adhesive and oxidation at elevated temperatures. [Copyright &y& Elsevier]

In this work, the Cr-Ti-Mo ternary o -MAX ceramics based on the Cr 2 TiAlC 2 phase are synthesized, and their tribological performance at elevated temperatures up to 800 ºC in the air is evaluated. With Si 3 N 4 as a tribocouple, an unexpected ultra-low wear rate reaching 6.1 × 10−8 mm3 N−1 m−1 is observed in Cr 1.9 Ti 0.9 Mo 0.2 AlC 2 at 800 ºC, accompanied by a stable coefficient of friction (COF) around 0.33 in a wide temperature range. X-ray photoelectron spectroscopy (XPS) depth profiling confirms a tribofilm with gradient composition, which simultaneously offers fluid lubricating at elevated temperatures and self-healing after cooling. Particularly, confirmed by the theoretical simulations, the doping of Mo improves the interlayer binding as well as alters the oxidation behaviors of Cr 2 TiAlC 2. With an optimal interlayer binding strength and oxidation rate, the Cr 1.9 Ti 0.9 Mo 0.2 AlC 2 can generate a tribofilm possessing ideal composition, which simultaneously promotes lubrication and anti-wear performance at elevated temperatures. [ABSTRACT FROM AUTHOR]

Ceramic design based on reducing friction and wear-related failures in moving mechanical systems has gained tremendous attention due to increased demands for durability, reliability and energy conservation. However, only few materials can meet these requirements at high temperatures. Here, we designed and prepared a Sn-containing Si 3 N 4 -based composite, which displayed excellent tribological properties at high temperatures. The results showed that the friction coefficient and wear rate of the composites were reduced to 0.27 and 4.88 × 10−6 mm3 N−1 m−1 in air at 800 °C. The wear mechanism of the sliding pairs at different temperatures was revealed via detailed analyses of the worn surfaces. In addition, the tribo-driven graphitization was detected on the wear surfaces and in the wear debris, and the carbon phase was identified by SEM, TEM, and Raman spectrum. [ABSTRACT FROM AUTHOR]

[Display omitted] Shear thickening fluids (STFs) have been the research focus for decades because of the prospect as a damping ingredient. However, their inherent liquid character confines their practical applications. In this work, inspired by the assembly engineering, novel gelatinous shear thickening fluids (GSTFs) are fabricated by integrating low molecular weight gelators (LMWGs) into STFs and investigated by rheological experiments. The results show that the apparent performances of GSTFs are determined by the LMWGs content. LMWGs inside GSTFs can assemble into three-dimensional network that can constraint the flowability of liquid molecular and their content dominate the density and strength of assembly network. At a moderate content, GSTFs exhibit desired properties with restricted quasi-static flowability and almost undamaged dynamic shear thickening character. While a higher content will disappear shear thickening and a lower content cannot gelate STFs. Besides, three different LMWGs are employed to gelate STFs and all they can gelate STFs in spite of the distinct minimum gelation concentration, indicating the universality for GSTFs preparation and the superiority of a reasonable molecular structure of LMWGs. Further, the temperature sweep experiments suggest that GSTFs can endure higher temperature without flowing due to its higher gel-sol transition temperature. Basing on these advanced mechanical properties, we believe that the GSTFs with more expected characters have significance for the study of non-Newtonian fluids and will broaden the special application field of STFs. [ABSTRACT FROM AUTHOR]

Fabric composite materials face significant challenges in maintaining excellent tribological properties at high temperatures. This study employed photodeposition to deposit gold (Au) and copper (Cu) nanoparticles on the surface of titanium dioxide-coated jojoba oil microcapsules (TiO 2 @jojoba), yielding micro-nanostructured Au-TiO 2 @jojoba and Cu-TiO 2 @jojoba microcapsules. Subsequently, microcapsules participated in the in-situ polymerization of polyimide (PI), serving as crosslinking points in PEEK/PTFE fabric-reinforced composites. PEEK/PTFE-Au composites containing Au-TiO 2 @jojoba microcapsules exhibited outstanding tribological and mechanical properties. Compared to microcapsule-free samples, PEEK/PTFE-Au composites showed a 30.26 % reduction in friction coefficient at 250 °C and a 24.28 % increase in tensile strength. In addition, mechanistic studies indicated that TiO 2 underwent a friction chemical reaction converting to TiNF during friction accompanying by friction-induced phase transitions. The release of jojoba oil during friction and the occurrence of friction chemical reactions were the main friction reduction mechanisms of PEEK/PTFE-Au composites at high temperatures. [ABSTRACT FROM AUTHOR]

Elucidating the tribological behaviors of CoCrNi-based high-entropy alloys (HEAs) at cryogenic temperatures is crucial for their practical application. This work uncovers the correlation between the wear-induced microstructural evolutions and tribological properties of single-phase CoCrFeNiMn HEA and heterogeneous CoCrFeNiAl HEA upon two contact conditions at 173 K. When CoCrFeNiMn HEA matches with GCr 15 rather than Si 3 N 4 , low contact stress and high flash temperature suppress the inhomogeneous deformation initiated by martensitic transformation and in turn create a gradient nanograined tribo-layer activated by high-density dislocations and nano-scale deformation twins, which progressively accommodates the frictional strain and reduces wear by an order of magnitude. Instead, the tribological properties of the CoCrFeNiAl HEA sliding against Si 3 N 4 are slightly superior to those sliding against GCr 15 , owing to the elevated contact stress and reduced flash temperature thicken the protective recrystallized nanocrystalline tribo-layer. Our findings offer guidance for optimizing the tribological properties of HEAs in cryogenic environments. [ABSTRACT FROM AUTHOR]

Fe3Al composite materials with 40, 60 and 80 wt.% Fe3AlC0.5 were fabricated by self-propagating high temperature synthesis (SHS) casting processing and analyzed with X-ray diffraction (XRD) and scanning electron microscopy (SEM). Microhardness, bending strength and wear rate of the composites were measured. The materials mainly consisted of Fe3Al and Fe3AlC0.5 phases. The adherence of the reinforcement and the matrix was good. There were no cracks at the interface of the phases in the materials. Hardness of the composites increased with Fe3AlC0.5 fraction. Bending strength of the composites was high and that of the composite with 60 wt.% Fe3AlC0.5 was the highest. Wear rates of the composites were low and those of the composites with 60 and 80 wt.% Fe3AlC0.5 were lower than that of the composite with 40 wt.% Fe3AlC0.5. [Copyright &y& Elsevier]

Herein, the porous graphite carbon nanospheres loaded with corrosion resistance (MBT@PCNs) were fabricated by carbonizing hypercrosslinked polystyrene nanospheres at 2450 °C, and then loaded and bonded with corrosion inhibitor 2-mercaptobenzothiazole (MBT) via the hierarchical porous structure of PCNs and grafting polydopamine layer. Porous carbon nanospheres (PCNs) are highly graphitized at ultrahigh carbonization temperature of 2450 °C, which is helpful to improve the wear resistance of 500SN due to the weak interlaminar shear force. Moreover, the MBT@PCNs have a sustained-release performance for corrosion inhibitor MBT. MBT molecule can be adsorbed on the substrate surface to achieve good anti-corrosion properties. Hence, MBT@PCNs can effectively enhance the anti-friction and anti-wear performance of 500SN under the combined effects of ball bearing, filling, and protective film. [Display omitted] • MBT@PCNs are fabricated by carbonizing HPSs at 2450 °C and loading with corrosion inhibitor. • 2.5 ppm MBT@PCNs can sustained-release 0.386 ppm of MBT. • The MBT@PCNs can reduce the COF to 0.104, and the wear volume is reduced by 97.0%. [ABSTRACT FROM AUTHOR]

High‐performance materials for 3D printing are increasingly desired to meet more and more requirements from various fields including aerospace and high‐tech equipment. In this study, 3D printing of isocyanate ester thermosets with high performances, such as excellent mechanical properties and thermal resistance, is realized with a facile method. A precursor of acrylate isocyanate ester with good photocuring capability is first synthesized with the reaction of tolylene‐2,4‐diisocyanate and hydroxypropyl acrylate. Then, mixed with diluent NeoRad U‐6282 and photoinitiator Irgacure 819, it forms ultraviolet curable resins for 3D printing. The digital light processing 3D printing of the resins results in high‐precision 3D structures, which finally turn out high‐performance thermoset materials after the cross‐linking of isocyanate groups at elevated temperature. 3D printing of isocyanate ester thermosets with high printing accuracy, excellent mechanical properties, and good heat resistance will expand the applications of 3D printing by meeting the high demands from many industries on both mechanical and thermal performance. [ABSTRACT FROM AUTHOR]

In this work, a dense Si 3 N 4 -based composite was fabricated by spark plasma sintering the mixture of Si 3 N 4 and Ti 3 AlC 2. The nitrogen atoms of Si 3 N 4 diffused into the TiC x lattice and leaded to the in-situ formation of TiC 0.3 N 0.7 and SiC compounds. After annealing in air at 900 °C, TiC 0.3 N 0.7 was oxidized to form rutile-TiO 2 particles (about 3–4 μm). Meanwhile, it was found that the oxidized composite displayed superior mechanical and tribological properties, compared to Si 3 N 4 and Si 3 N 4 -based composite before oxidation. Typically, the fracture toughness reached 9.97 MPa m1/2, which was 59.5% higher than that of Si 3 N 4. In addition to cracks branch, bridge and deflection, the surface barrier of oxides was another major toughening mechanism. Besides, due to the pinning effect of TiC 0.3 N 0.7 , sliding-induced microcracks were completely suppressed, and the composite exhibited excellent friction and wear performances. In this case, the composite is expected to be fabricated into ceramic parts for service in high temperature environment. [ABSTRACT FROM AUTHOR]

Lead-bismuth eutectic liquid metal (LBE) is the primary coolant for the advanced liquid-metal nuclear reactor, and clarification of its lubrication behavior and mechanism at elevated temperature is of importance. In this paper, a self-mated high-temperature steel sliding-pair and a pin-on-disc configuration are selected to evaluate the lubrication behaviors of LBE at 250 °C and 400 °C under argon atmosphere. It is found that LBE possesses an excellent lubricity proofed by the low friction coefficient of 0.1 and the wear rate of 10−6 mm3/Nm for the steel discs. Close inspection on the friction interfaces indicates that the worn surfaces of the steel discs are covered by a smooth tribo-film consisting of Bi, Pb 7 Bi 3 and the related oxides. • The high-temperature lubricity of Lead-bismuth liquid metal (LBE) for the nuclear coolant was studied. • LBE presents an outstanding lubricity for the high-temperature steel at 250 and 400 °C. • The formation of a Bi/Pb 7 Bi 3 /oxides self-lubricating tribo-layer provides the lubricity. [ABSTRACT FROM AUTHOR]

The β-Sialons are potential candidates for high temperature application because of their excellent comprehensive performances. However, there is little research about dry sliding wear behavior of β-Sialons at wide range temperature. This study aims at revealing the mechanisms of how temperature, microstructure and mechanical properties affect the tribological properties of such composites. Four kinds of β-Sialons are prepared and their wear properties are characterized from 25 to 800 °C. Results show that β-Sialons have a preferable tribological property at 25 °C, which is ascribed to its excellent mechanical properties. Whereas, with temperature increasing, the wear rate increases two orders of magnitudes compared to 25 °C, owing to the reduced hardness and increased thermal stress of the sample. At 800 °C, the wear rate of composites decreases with z values increasing, which is attributed to the tribo-chemical reaction and generate more Al 2 O 3 in β-Sialons with higher z values during sliding process. [ABSTRACT FROM AUTHOR]

In aerospace, some moving parts will meet with simultaneous high temperature and vacuum environments. In this study, the tribological behavior of a nickel alloy matrix solid lubricant composite was contrastively investigated under both air and vacuum conditions from room temperature to 800 °C. Results showed that both the friction coefficient and the wear rate of the composite were highly dependent on testing temperature and atmosphere. The friction coefficient in vacuum was lower than that in ambient air. The compositions of the frictional surfaces were analyzed, based on which, the mechanism of friction and wear was proposed. [ABSTRACT FROM AUTHOR]

Effect of Si addition on the high temperature tribological properties of TiZrV 0.5 Nb 0.5 refractory high entropy alloy was systematically studied. The results demonstrate that Si-microalloying affects the tribological properties by modulating the evolution of tribo-layer. Si-microalloying produces local tribo-layer with strong wear resistance by increasing the sintering rate of wear debris below 600 ℃, ultimately significantly reducing the coefficient of friction and wear rate. At 600 °C, Si-microalloying deteriorates the wear resistance due to the stress concentration at hard particles leading to accelerated fracture of the tribo-layer which hinders the formation of continuous protective tribo-layer. The enhanced tribological properties at 800 °C are attributed to the synergistic effect of suppressed oxide volatilization and rapid oxidation behavior ensuring continuous dense tribo-layer formation. • The high temperature tribological properties of TiZrV 0.5 Nb 0.5 Si x RHEA was studied. • The evolution of the tribo-layer plays a crucial role in the wear process. • The sintering rate of debris determines the formation of tribo-layer below 600 ℃. • A continuous and dense tribo-layer was formed for the Si0.3 alloy at 800 °C. [ABSTRACT FROM AUTHOR]

Inherent strength-plasticity tradeoff and unfavorable anti-wear capacity of FCC-structured high-entropy alloys (HEAs) bottlenecks their applications in advanced industries. This work controllably deployed an enhanced heterostructure and graded grain distribution in the single FCC-phase HEA model according to the concept of selective solid solution, which contributed to the ultrahigh compressive strength at appreciable plasticity levels for allowing worn surface to accommodate tribological loading. Simultaneously, the multiscale FCC-coupled architecture with compositional fluctuation effectively inhibits high temperature softening and activates the in-situ tribochemistry protection of the duplex glaze-layer and recrystallized subsurface, reaching low wear between room-temperature and 800 °C. Our alloying strategy offers a novel avenue for further governing mechanical-tribological combined properties in applicable metallic systems. [Display omitted] [ABSTRACT FROM AUTHOR]

The thermal stability of polymer matrix composite could effectively improve by incorporation of highly thermally conductive ceramic materials into polymers. In present work, hybrid PTFE/Nomex fabric/phenolic composite specimens were prepared with zirconium diboride (ZrB 2 ) particles for the improvement its high-temperature tribological performances. The thermal stability of hybrid PTFE/Nomex fabric/phenolic composite was investigated by TGA. The result showed that the thermal stability was improved because of addition of ZrB 2 particles. In addition, it was found that 9 wt% ZrB 2 reinforced hybrid PTFE/Nomex fabric/phenolic composite exhibited optimal tribological performances compared to unfilled fabric composite under all test conditions. [ABSTRACT FROM AUTHOR]

The tribological behaviors of the (W 0.67 Al 0.33 )C 0.67 –Co/fluoride (CaF 2 , BaF 2 , CaF 2 /BaF 2 ) composites against SiC ball from room temperature to 600 °C were investigated. A marked increase in the friction coefficient resulting from fluoride oxidation was observed as the temperature increased. The composites containing BaF 2 or (Ca, Ba)F 2 displayed better integrated wear resistance over a wide temperature range compared with (W 0.67 Al 0.33 )C 0.67 –Co/CaF 2 . The high temperature tribological characteristics of the three composites were distinct, which originated from the composition difference on the worn surfaces. First, the SiO 2 /SiC film formed on the worn surfaces of the composites with BaF 2 or (Ca, Ba)F 2 was favorable for their wear resistance. Second, the oxidation of WC matrix was an important factor influencing the wear resistance of the composites. When mixture oxides of WO 2 and WO 3 appeared on the surface, wear is severe. In addition, single WO 3 formed on the worn surfaces, appeared more adhesive to the underlying substrate and decreased the wear rate. [ABSTRACT FROM AUTHOR]

In this paper, the dry-sliding tests of Ti 3 AlC 2 /SiC tribopairs were conducted from 25 °C to 1000 °C in both air and argon atmospheres for confirming the roles of tribo-oxidation and laminate structure of Ti 3 AlC 2 . The characteristics of the worn surfaces of the Ti 3 AlC 2 were contrastively examined and the corresponding tribological mechanisms were discussed. Ti 3 AlC 2 showed distinctive tribological behaviors and mechanisms in the two atmospheres. Here, the tribo-oxidation film played a very vital role for the tribology of Ti 3 AlC 2 . In air, Ti 3 AlC 2 showed moderate wear at 25–400 °C and Ti 3 O 5 was the major phase of the tribofilms. At 600–1000 °C, the wear-resistant tribo-oxidation films, consisting of TiO 2 and Al 2 O 3 , were believed to be responsible for the negligible wear. In argon, Ti 3 AlC 2 exhibited heavy wear in the whole temperature range. Abrasive and adhesive wear caused the poor tribological performances at 800 °C and below. At 1000 °C, Ti 3 AlC 2 displayed plastic flowing and large furrows under the shear stress. [ABSTRACT FROM AUTHOR]

Producing fabric composites with improved high-temperature tribological property is highly desired for their use in practical application, yet still challenging. Herein, we employed MoSi 2 as anti-oxidant and filled it into the hybrid PTFE/Nomex fabric/phenolic composite. The high-temperature tribological properties of the fabric composites were evaluated on a pin-on-disk tribometer. The results showed that the MoSi 2 filled fabric composites displayed much lower wear rates in high-temperature environment, comparing to that of unfilled fabric composite. Moreover, the antiwear property of the MoSi 2 filled fabric composite can be further improved by treating the fabric with air-plasma, as the bonding strength between the fabric and resin was evidently enhanced. The wear behaviors and the corresponding wear mechanisms of the composites were discussed based on the characterizations. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a series of ZrO2 matrix high-temperature self-lubricating composites were prepared by hot-press technique. The effect of Mo and Ag on the friction and wear behavior of the ZrO2(Y2O3)–Ag–CaF2–Mo composites in a wide temperature range was investigated. The XRD results showed that CaMoO4 formed on the worn surface above 400°C. The excellent lubrication performance of CaMoO4 endowed the low coefficient of friction of the ZrO2(Y2O3)–Ag–CaF2–Mo composites at high temperatures. The ZrO2(Y2O3)–10Ag–10CaF2–10Mo composites showed favorable wear resistance at all the tested temperatures which was attributed to the combined action of hardness and phase transformation. [Copyright &y& Elsevier]

High-temperature self-lubricating nickel-alloy based composites with Ag and three amounts of BaF2/CaF2 eutectic were prepared by hot press sintering technique. Both the composites with 5wt% and 10wt% BaF2/CaF2 eutectic exhibited markedly higher strength than 15wt% composite. The friction coefficient of the three composites was comparable. All three composites showed the highest wear rate at 600°C, but very lower at 800 and 900°C. The friction coefficient of the three composites was slightly lower as sliding against Si3N4 than Inconel 718. The friction and wear mechanism was proposed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, ZrO2 matrix high-temperature self-lubricating composites with addition of CuO as lubricant were prepared using a hot-pressing method by tailoring the content of CuO. The wear and friction behaviour of the composites were investigated from 700°C to 1000°C. The composites sliding against an Al2O3 ceramic ball exhibited excellent self-lubricating and anti-wear properties at high temperatures. The low friction and wear mechanisms were investigated in detail. [Copyright &y& Elsevier]

Abstract: Two kinds of lithium-based and sym-triazine- or cyclotriphosphazene-functionalized ionic liquids (ILs, L-C3N3 and L-P3N3) were synthesized by simply blending an appropriate molar ratio of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with tri(methoxyethoxyethoxyethoxy)triazine (C3N3(OR)3) or hexa(methoxyethoxyethoxyethoxy) cyclotriphosphazene (P3N3(OR)6). The ILs were evaluated as high temperature lubricants for Si3N4/steel contact and found to have significantly improved friction–reducing and anti-wear proprieties compared with conventional alkylimidazolium ILs, 1-ethyl-3-methylimidazolium bis(trifluoro methylsulfonyl)imide (L-F102) and 1-butyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide (L-F104), at some condition. The morphologies of the worn surfaces were analyzed by scanning electron microscope (SEM). The wear mechanisms were discussed according to the surface composition analysis by X-ray photoelectron spectroscopy (XPS). [Copyright &y& Elsevier]

In this paper, we reported the tribological behavior of TiAlC disk sliding against SiC ball from room temperature (RT) to 1,000 °C. The tribological properties are highly dependent of testing temperature. At RT, the coefficient of friction (CoF) is as low as 0.34 in the steady state, but the wear rate is relative high (4.26 × 10 mm/Nm). At 200 and 400 °C, the CoF is as high as 1.21, and the wear rates are very high, about on the order of 10 mm/Nm. From 600 to 1,000 °C, however, TiAlC exhibits quite low wear rate on the order of 10 mm/Nm and relative moderate CoF, 0.60-0.80. The compacted continuous oxide layer at 600 °C and above might be responsible for the outstanding wear resistance. [ABSTRACT FROM AUTHOR]

Abstract: The high-temperature tribological behaviour of Fe–28Al–5Cr alloy and its composites containing TiC was investigated against a Si3N4 ceramic from 25 to 800°C. The high-temperature wear resistance of the materials was significantly improved by the addition of TiC, which was attributed to the high hardness of the composites, as well as the support role of hard TiC. The oxidation played an important role to friction and wear. [Copyright &y& Elsevier]

It is a challenge to design self-lubricating materials that exhibit and maintain reduced friction coefficient as well as high strength over a wide range of temperatures. A high-temperature self-lubricating nickel-alloy-based composite was created using the hot pressing technique. The composite exhibited high relative density, and simultaneously superior lubricating properties, average friction coefficient below 0.25 from room temperature to 800 °C, and high strength, 470 MPa of tensile strength and 1500 MPa of compressive strength. The composite was very promising in high-temperature tribology. [ABSTRACT FROM AUTHOR]

Abstract: ZrO2 (Y2O3) with different contents of BaF2/CaF2 and Mo were fabricated by hot pressed sintering, and the tribological behavior of the composites against SiC ceramic was investigated from room temperature to 1000°C. It was found that the ZrO2 (Y2O3)–5BaF2/CaF2–10Mo composite possessed excellent self-lubricating and anti-wear properties. The low friction and wear were attributed to enhanced matrix and BaMoO4 formed on the worn surfaces. [Copyright &y& Elsevier]

Abstract: The Ni3Al matrix high temperature self-lubricating composites with different particle size were fabricated by the powder metallurgy technique. The effect of particle size on the mechanical and tribological properties of the composites was investigated in this paper. The results showed that the coarse particle composite exhibited the lowest friction coefficient and wear rate compared to the fine particle ones at a wide temperature range from room temperature to 1000°C. The reason for the low wear rate was that the coarse bulk phase could provide better deformation resistance and higher load bearing capacity than the fine microstructure. [Copyright &y& Elsevier]

Abstract: High temperature self-lubricating composites Ni3Al–BaF2–CaF2–Ag–Cr were fabricated by powder metallurgy technique. In this paper the effect of Cr content on tribological properties at a wide temperature range starting from room temperature to 1000°C was investigated. It was found that Ni3Al matrix composite with 20wt% Cr exhibited low friction coefficient of 0.24–0.37 and a wear rate of 0.52–2.32×10−4 mm3 N−1 m−1. Especially at 800°C it showed the lowest friction coefficient of 0.24 and a favorable wear rate of 0.71×10−4 mm3 N−1 m−1. This implied that 20wt% Cr was the optimal Cr content and its excellent tribological performance could be attributed to the balance between strength and lubricity. [Copyright &y& Elsevier]

Abstract: In order to improve the lubrication performance and inhibit the serious corrosivity of conventional ionic liquids (ILs) at elevated temperatures, a series of vinyl functionalized ILs were synthesized in this work. The corrosion behavior of the ILs was evaluated with copper sheet corrosion test and their tribological properties were investigated on an Optimol SRV-IV oscillating friction and wear tester at elevated temperatures. The results showed that ILs with vinyl group, such as 1-vinyl-3-butyl imidazolium tetrafluoroborate (VBImBF4), can reduce corrosion effectively and its extreme pressure reached up to 1500N at 150°C. Based on the XPS analysis, ILs with vinyl group could interact with the iron surface and a protecting layer would form on the surface of steel possibly. Thus, ILs lubricants with good lubricating performance and low corrosivity at elevated temperature were achieved. [Copyright &y& Elsevier]

Abstract: A Ni3Si–Cr7C3 composite coating was fabricated on AISI 1020 steel substrate by self-propagating high-temperature synthesis (SHS) casting route. Phase composition, microhardness and dry sliding wear behavior of the coating were studied. The results indicated that the coating was mainly consisted of Ni3Si and Cr7C3. The microhardness of coating is about 900HV. The friction and wear tests showed that although the friction coefficient had no obvious change, the wear resistance of the AISI 1020 steel matrix was improved greatly. Also, the corrosion test result showed that the coating had an excellent corrosion resistance. [Copyright &y& Elsevier]

Abstract: A simple and conventional coating-curing process to fabricate superhydrophobic coating surface with both the micro-nano-scale binary structure (MNBS) roughness, and the lowest surface energy hydrophobic groups (−CF3) on engineering materials of stainless steel or other metals was developed by control of curing conditions. Results show that higher temperature and longer cooling time resulted in longer crystallizing process, and the forming PTFE aggregates could slowly produce the crystallization and create the willow-leaf-like or wheat-haulm-leaf-like polymer micro/nano-fiber on the atop surface. The curing temperature dramatically influences the micro/nano-fiber texture of the PTFE/PPS superhydrophobic coating surface, leading to the excellent superhydrophobicity at higher temperature. An increase of the curing temperature is beneficial to fluorine gradient-distribution, PPS thermal-oxidative cross-linking and oxidative reaction, resulting in the enhancement of adhesive strength and mechanical properties of the PTFE/PPS superhydrophobic coatings. A bionic superhydrophobic surface with porous gel-like network and PTFE micro/nano-fiber textures could be created by natural cooling in air, whereas PTFE nano-sphere/-papillates textures could be fabricated by hardening in H2O. [Copyright &y& Elsevier]

• Mechanical and tribological behaviors of CoCrNi MEA are tuned by heterogeneous (Al,Ti). • Heterogeneous (Al,Ti) boosts the strength-plasticity synergy via solute strengthening. • Heterogeneous (Al,Ti) amplifies the wear of CoCrNi MEA at intermediate temperature. • Top glaze-layer enriched in (Al,Ti) contributes to high wear resistance at 800 °C. CoCrNi medium-entropy alloys (MEAs) system has been hailed as the potential high strength and ductile structural materials. However, the study on their tribological behaviors over a wide temperature range is still scarce. The current work investigates the effects of heterogeneous (Al, Ti) on the phase evolution, mechanical and high-temperature tribological performances of the MEAs. (Al, Ti) endows the MEAs a considerable solutal effect, which triggers the transformation from FCC-dominated single-phase structure to dual heterostructure containing FCC matrix and yarn-like structures/coupled BCC phases. Our designed MEA has an ultrahigh compressive yield strength of 2.0 GPa and a plasticity of 12.3%. Tribological properties of the designed MEA are temperature dependent. (Al, Ti) enhances the wear-resistance of MEA by five times due to the mitigation of abrasive wear below 400 °C. While between 400 °C and 600 °C, (Al, Ti) intensifies the adhesive wear instead, leading to severe wear. When it reaches 800 °C, (Al, Ti) will induce the tribo-chemistry to form the lubricative glaze-layer that minimizes wear. [ABSTRACT FROM AUTHOR]

• Multifunctional lubricant additive GCN@M16 with corrosion resistance are obtained. • The porous hollow structure of GCN@M16 could effectively control the release of M16. • Excellent tribological properties were achieved via synergy effect of GCN and M16. • Protective films were formed by GCN@M16 via complex physicochemical reaction. This study deals with the preparation and analysis of a novel corrosion inhibitor-infused hollow porous graphite carbon nanosphere (GCN@M16) interposed with a corrosion inhibitor devised with a controlled release mechanism (M16), which was synthesized under ultrahigh carbonization temperature of about 2100 °C and via consequent organic corrosion inhibitor loading. A comprehensive analysis of the tribological and anti-corrosion properties of GCN@M16 was conducted pertaining to this nanosphere being employed as a lubricant additive in 500SN base oil. The as-prepared GCN (Graphitized Carbon Nanospheres) tend to be endowed with low friction coefficients attributable to the high graphitization of carbonaceous matter. The M16 loading not only enhances the dispersion level of GCN in 500SN base oil, but also empowers them as corrosion inhibitors by strengthening their corrosion resistance ability. Furthermore, the porous hollow structure of the novel GCN facilitates the effective regulation of the release of M16 loading, resulting in the prolonged service life of friction pairs. Subsequently, the mechanism of friction reduction and the anti-wear properties of GCN@M16 were deduced. GCN@M16 is capable of effectually forming a stable protective film over the contact surface via a complicated tribo-chemical reaction and physical mechanical deposition. Reflecting the synergistic effect produced by GCN and M16, the as-obtained GCN@M16 tends to exhibit excellent tribological performance, including high extreme pressure up to 950N, low friction coefficient of around 0.06, and fine anti-abrasion (94.3% reduction), and anti-corrosion properties. The results derived in this paper could prove highly beneficial and provide fundamental insights about the formation of lubricating films, as well as stimulate the industrial application of similar versatile lubricant additives. [ABSTRACT FROM AUTHOR]

High entropy alloys (HEAs) are an important candidate for high temperature mechanical systems. Here, effects of atmosphere, temperature and counterparts on the vacuum tribological behaviors of CoCrFeNi HEA fabricated by spark plasma sintering were systematically studied. Comparison of tribological behaviors in vacuum and air indicated that tribo-oxidation is detrimental to the wear resistance of CoCrFeNi HEA within temperature range 25–400 °C, but positive at 600 and 800 °C. The CoCrFeNi HEA obtains relatively low wear in vacuum when low testing temperatures and heterogeneous counterface are selected. The wear resistance of CoCrFeNi HEA in vacuum is superior or comparable to the steel and intermetallics. • The high-temperature tribological behaviors of CoCrFeNi HEA were studied. • Tribological properties of HEA depend on atmosphere, temperature and counterparts. • Tribo-oxidation is negative for the wear resistance below 600 °C but positive above. • In vacuum, surface oxidation, adhesive and mechanical properties determine the wear. [ABSTRACT FROM AUTHOR]

Abstract: Bulk Al2O3 dispersed ultrafine-grained (UFG) Cu matrix composite has been fabricated by self-propagating high-temperature synthesis (SHS) casting route. The microstructures and mechanical properties of the as-fabricated materials have been investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis, and microhardness measurements and compression tests, respectively. The results show that the as-fabricated material has small amount of entrapped Al2O3 particles in uniform microstructure Cu having a grain size ranging from 200–500 nm with an elevated compressive yield stress (298 MPa) and an improved microhardness value (1.06 GPa). The possible strengthening mechanism of the product has been discussed. [Copyright &y& Elsevier]