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The incorporation of rare earth oxides and nano-silica has been found to significantly enhance the mechanical and tribological characteristics of phenolic-based hybrid nanocomposites. In this work, the impact of these additives was investigated through single-factor experiments. The study revealed that cerium oxide and yttrium oxide were the primary factors influencing changes in the impact strength, shear strength, coefficient of friction, and wear rate. Additionally, the content of nano-silica exerted the most substantial influence on the hardness and compressive strength of the specimens. Furthermore, the material ratios of the phenolic-based hybrid nanocomposites were optimized using an orthogonal experimental design and a fuzzy comprehensive evaluation method. The optimal material ratio for these nanocomposites was determined to be 2% cerium oxide, 2.5% yttrium oxide, and 3% nano-silica, based on their mechanical, frictional, and wear properties. This research provides valuable insights for the development of new brake friction materials with low friction and high wear resistance and contributes to meeting the demand for polymer composites with superior mechanical performance in diverse applications. [ABSTRACT FROM AUTHOR]

Using plasma surfacing in a nitrogen environment with a PP-R18U non-current-carrying flux-cored wire, the layers up to 10 mm thick were formed on a 30HGSA steel, followed by an additional high-temperature tempering (at 580°C for 1 hour in 4 tempers). It is shown that the deposited layer has a frame-type structure formed by α-iron grains with extended layers of the Fe3W3C (M6C) carbide phase located along the boundaries. Nanosized particles of carbides of the V4C3, Cr7C3, Fe3C, Cr23C6 and WC1–x types are identified in the grain volume. It is found out that high tempering increases the microhardness of the deposited PP-R18U layer by 13% (up to 5.3 GPa) and decreases its wear resistance by 12.3% the friction coefficient by 7.7%. [ABSTRACT FROM AUTHOR]

The mechanical behavior of Al–Fe–Cr aluminum matrix composites strengthened by nanoquasicrystalline and/or crystalline phases was studied in the temperature range of 77–573 K. The strength characteristics and elongation to fracture during tensile tests of Al94Fe2.5Сr2.5Ti1, Al94Fe2Cr2Ti2, Al94Fe2.5Сr2.5Ti0.7Zr0.3 alloys were determined. It was established that the Al94Fe2Cr2Ti2 composite alloy has the highest strength (σb ≥ 3.87 GPa) among wrought aluminum alloys with satisfactory plasticity (elongation to fracture δ ≥ 5% at 293 K) at the temperature of 573 K. Tribological tests have shown that the wear resistance of Al–Fe–Cr aluminum matrix composites is significantly higher in the case of lubrication than when dry friction occurs. In lubrication, the friction force is almost 5 times less as well. The Al94Fe2Cr2Ti2 composite is optimal by the combination of mechanical and tribological properties among the studied alloys due to the strengthening of the aluminum matrix by nanoparticles with both crystalline and quasicrystalline structures. [ABSTRACT FROM AUTHOR]

The purpose of the present work is to assess the effectiveness of a low-cost and environmentally friendly chemical modification of sisal fibers based on the usage of sodium citrate (SC) and stearic acid (SA) on the thermal, mechanical, tribological and morphological characteristics of sisal fiber reinforced epoxy composites (SREC). Scanning electron microscopy (SEM) was used to investigate the morphological properties of the sisal fibers, which demonstrated that the chemical treatment eliminated the contaminants from the fibers' surface. The reduction of hemicellulose and lignin contents of the fiber was confirmed by Fourier transform infrared (FTIR) analysis following both chemical treatments. Thermal stability of the treated fibers showed a slight reduction as revealed by Thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC). Mechanical properties like tensile, flexural and inter-laminar shear strength showed appreciable improvement for the SA treated SREC (8.05%, 8.50% and 29.42%) and SC treated SREC (23.27%, 13.13% and 51.02%) when compared to untreated SREC. Furthermore, the tribological behaviour of the composites reinforced with treated fibers showed improved wear resistance and frictional properties in comparison to untreated composites. To better understand the fiber/matrix adhesion, morphological examinations of fracture and worn surfaces of composite samples were done using SEM. The test results suggest that the sodium citrate treatment is superior to the stearic acid treatment in improving the composites' mechanical and tribological properties. [ABSTRACT FROM AUTHOR]

This article reports the results of comparative studies of the composition, structure, high-temperature oxidation resistance, mechanical and tribological properties of (MoTaNbZrHf)-Si-B coatings prepared at an identical average power of 1 kW by direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HIPIMS). Switching from the DCMS to the HIPIMS mode is found to increase adhesion and crack resistance of the coatings and their wear resistance under friction sliding and cyclic impact conditions, as well as reduce the depth of oxidation at 1300 °C threefold. The record-breaking values of high-temperature oxidation resistance at 1500 °C are achieved due to formation of a surface film based on the borosilicate glass (a-Si:B:O) containing crystallites of the t-HfSiO 4 , o-Ta 2 O 5 , m-HfO 2 , and m-ZrO 2 phases. [Display omitted] • A multilayer target with a (MoTaNbZrHf)-Si-B working layer was produced. • DCMS and HIPIMS coatings exhibited a hardness of 13–14 GPa. • The transition from DCMS to HIPIMS improves crack- and wear resistance. • The coatings demonstrated high oxidation resistance at 1100–1500 °C. [ABSTRACT FROM AUTHOR]

Fluorographene (FG) with layer numbers of 3–4 was successfully prepared through facile microwave‐assisted liquid phase exfoliation of raw graphite fluoride (GrF). The raw GrF and the as‐prepared FG were then directly incorporated into polyamide 66 (PA66) by melt processing without using any surfactants. Microstructural, mechanical and tribological properties of the prepared PA66 composites were investigated. Various characterization results showed that both GrF and FG, as novel solid lubricants, can effectively improve the mechanical and anti‐wear performances of the PA66 matrix. It was also found that FG is better at improving mechanical properties and reducing the friction of PA66 than GrF at low concentrations owing to the large surface–volume ratio. The addition of 0.5 wt% FG into PA66 exhibits a ca 13% increase in tensile modulus, ca 5% increase in tensile strength, ca 18% reduction in coefficient of friction (COF) and ca 43% reduction in wear rate. However, at relatively high concentrations, such as 1.0 wt%, GrF shows a better reinforcement effect than FG owing to a uniform dispersion of GrF in the PA66 matrix. The addition of 1.0 wt% GrF into PA66 exhibits a ca 18% increase in tensile modulus, ca 5% increase in tensile strength, ca 37% reduction in COF and ca 46% reduction in wear rate. Wear tests also show that the excellent wear resistance of the PA66 composites is due to the improved mechanical properties and the lubrication of GrF and FG between the worn surfaces. Our current work demonstrates the tremendous potentials of fluorinated carbon materials for enhancing mechanical and anti‐wear properties of polymeric materials. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

High-entropy bulk metallic glasses (HE-BMGs) with desired thermal stability often exhibit limited plasticity due to the occurrence of shear localization avalanches. The present study reports the fabrication of a novel composite TiZrHfNb 0.5 Cu 0.5 Be 0.5 , consisting of a high entropy crystalline phase (TiZrHfNb) and an amorphous matrix (TiZrHfCuBe). The composite exhibits a distinctive combination of strength and ductility, surpassing that of traditional BMG composites, along with a notable capacity for work-hardening. Furthermore, it demonstrates exceptional wear resistance under varying normal loads or frequencies. The deformation and wear mechanisms are attributed to the solid-solution strengthening and stress-induced β → α " martensitic transformation in the high entropy crystalline phase, as well as the deformation-induced crystallization in HE-BMG matrix. These findings would provide a new strategy for preparing advanced HE-BMGs composite with unique properties. • A composite TiZrHfNb 0.5 Cu 0.5 Be 0.5 , consisting of a high-entropy phase TiZrHfNb and an amorphous matrix TiZrHfCuBe is fabricated. • The composite has excellent strength-ductility combination, along with a notable work-hardening capacity. • The composite demonstrates exceptional wear resistance under varying normal loads or frequencies. • Deformation-induced crystallization nearby the crystal/amorphous interface is found during the deformation or wear process. [ABSTRACT FROM AUTHOR]

The primary objective of the present investigation is to examine the effects of air annealing on the mechanical, tribological, and structural properties of multilayer CrN/CrTiSiN coatings. The deposition of CrN/CrTiSiN multilayer coatings on a Ti6Al4V substrate was carried out using CAE-PVD technique. Subsequently, the as-deposited coatings were subjected to annealing in ambient air environment at a temperature of 600 °C for 1 h. The characterizaion purposes were achieved by XPS, XRD, FESEM, nanoindentation, Rockwell-C adhesion tests, and pin-on-disk wear tests. The results suggest that the annealing process led to the development of new Cr 2 N, Cr 2 O 3 , and SiO 2 phases. The coating hardness increased from 21.5 GPa to 25.3 GPa by annealing process. The findings from the pin-on-disc experiment indicate that the wear resistance of the annealed coating exhibited superior performance when compared to both the as-deposited coating and the substrate. The improvment could be attributed to the annihilation of the residual stress and the formation of new phases on the surface. • Annealing transforms CrN/CrTiSiN coating to Cr 2 N, Cr 2 O 3 , and SiO 2. • Hardness increases to 21.65 GPa, elastic modulus decreases to 334 GPa. • Post-annealing improves wear resistance due to reduced residual stress and formation of new phases. [ABSTRACT FROM AUTHOR]

Different approaches to formation of hard multicomponent coatings with improved tribological characteristics in a wide temperature range are considered. It is shown that deposition of a thin surface layer or introduction of additional structural components into nanocomposite coatings, which play the role of a solid lubricant, lowers substantially the friction factor and increases the wear resistance [ABSTRACT FROM AUTHOR]

Replacing Pb with low melting point Bi, Ni–P/Bi self-lubricating composite coating was successfully prepared using CuSn10 substrate by electroless plating. The microstructure and mechanical properties of Ni–P/Bi composite coating, Ni P coating, CuSn10 substrate and Pb-containing CuSn10Pb10 material were investigated, and the sliding friction experiment with 45 steel was conducted on M200 ring-block tribometer. Results show that compared with the CuSn10 substrate and CuSn10Pb10 material, the hardness of Ni P coating alloy and Ni–P/Bi composite coating alloy material is improved greatly. The coating alloy also enhances the impact toughness and crushing strength of CuSn10 substrate. Compared with the CuSn10Pb10 alloy, the friction coefficient and wear rate of Ni-P/Bi composite coated alloy are reduced by 40 % and 47 %, respectively. The wear surface of the Ni–P/Bi composite coating material is smooth and flat, which can remarkably improve the adhesion and tear wear of the wear surface of CuSn10Pb10 material. • Ni-P/Bi self-lubricating composite coating was successfully prepared on CuSn10 alloy. • Low melting point metal Bi is used in the coating instead of toxic CuPb alloy. • Ni-P/Bi composite coating increases the surface hardness from 178 HV to 560 HV. • Antifriction and wear resistance of Ni-P/Bi coated CuSn10Pb10 improve by 40 % and 47 %. [ABSTRACT FROM AUTHOR]

• Aqueous PAI-MoS 2 -graphite bonded solid lubricating coatings are novel green lubricated materials. • Aqueous coating with the MRGM of 0.3 exhibits more excellent mechanical and tribological properties. • Tribological mechanisms of aqueous coatings are systematically investigated concerning the morphology, structure and chemical compositions of wear scars. In this paper, a series of the environmental-friendly aqueous PAI-MoS 2 -graphite bonded solid-lubricating coatings (BSLCs) are prepared depending on the design concept of the recombination of two-component lubricant and aqueous resin, and the mechanical strength and wear resistance of the coatings are deeply optimized by virtue of the synergy of the components of coatings. The experimental results demonstrate that the successful preparation of aqueous BSLCs greatly reduces the utilization of toxic organic solvents and is conducive to environmental protection and resource conservation. Doping an appropriate amount of graphite into the aqueous BSLCs is beneficial to maximize the promotion of the mechanical and tribological properties of the coating, and when the mass ratio of graphite to MoS 2 (MRGM) is 0.3, the mechanical strength, friction reduction and wear resistance of the coatings display the comparable level as that of the organic-solvent based BSLCs. Based on the analysis of the variations of the morphology, structure and chemical composition of the wear scars, the corresponding active mechanisms on the mechanical and tribological properties of the coating are investigated in depth. [ABSTRACT FROM AUTHOR]

Metal-matrix composite (MMC) coatings are advanced materials, composed of two or more phases that can be tailored based on the industrial needs such as lightweight and wear-resistance. Cold spray (CS) technology is highly suitable to develop these MMC coatings as it is a low temperature deposition method, which does not involve particle melting, hence retaining the original properties of the materials. Ti–6Al–4V (Ti64) is a common alloy used in aerospace applications owing to its lightweight and high yield strength. Recently, cold sprayed Ti64 coatings have shown promise to repair damaged or enhance surfaces of Ti components. However, there are still several issues with cold sprayed Ti64 coatings, such as relatively high porosity level and low wear-resistance. To solve these, a novel approach is to incorporate CoCr (ASTM F75) as reinforcing metal alloy particles into the Ti64 matrix to form a Ti64–CoCr composite coating. Pure Ti64 and pure CoCr coatings were also deposited as a comparison. The Ti64–CoCr composite coating achieved low porosity level (0.9%), high hardness (434 HV) and high wear resistance (1.7 × 10−4 mm3/Nm) compared to the Ti64 coatings. These properties were obtained while maintaining the original phases of the feedstock Ti64 and CoCr powders and achieving adhesion strength above 60 MPa. A 20 nm thick Ti–Co interdiffusion layer was also observed at the interface of CoCr and Ti64 particles under TEM. These results showed that Ti64–CoCr composite coating is a promising lightweight and wear resistant metallic coating for aerospace application. [ABSTRACT FROM AUTHOR]