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A set of novel (AlTiCrVTa)N x coatings are synthesized by DC magnetron sputtering to methodically investigate the effect of nitrogen content on the microstructure, mechanical and tribological properties and oxidation behavior of the coatings for the first time. As the nitrogen content increases, the coating structure transitions from amorphous to a simple fcc structure, accompanied by a change of preferred orientation from (200) to (111) and an enhancement in crystallinity. The coating morphology changes from featureless glassy to columnar crystals. The highest nanohardness of 38.1 GPa and the best wear rate of 4.9 × 10−7 mm3/Nm are achieved at 43.3 at.% nitrogen content. The friction coefficient exhibits a downward trend with rising nitrogen content, reaching the lowest value of 0.47 at 49.8 at.% nitrogen content. The oxidation tests reveal that the oxidation resistance deteriorates with increasing nitrogen content, caused by the looser structure and large-sized grain boundaries. [ABSTRACT FROM AUTHOR]

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]

Egg shells and fish scales are two abundantly available by-products from food industries which can be used as filler materials to reinforce polymer composites. The bulk of discarded chicken eggshells and fish scales are disposed of in landfills, which cause environmental issues. The present research work focuses on the water absorption, mechanical and tribological properties of epoxy composites reinforced with chicken eggshells and catla fish scale particles. Hybrid composites incorporating both fillers were also made and evaluated. Results from the water absorption tests showed that the addition of fillers decreased the water absorption of the composites than neat epoxy. Tensile and impact tests revealed that the inclusion of fillers reduced the tensile and impact strength of the composites compared to neat epoxy, but improved the tensile modulus. The hybrid composite (EFREC) showed improvement in both flexural strength and modulus in comparison to neat epoxy. Also, the results from the wear tests revealed that the addition of fillers improved the wear resistance of the composites. Among all the mechanical and wear tested composite specimens, the hybrid composite (EFREC) showed the best performance. This was also validated from the SEM images of the fracture and wear surfaces of the composites. [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]

In this study, morphological and tribological analyses (optical microscopy, scanning electron microscopy as well as friction and wear tests) were used to investigate the properties of newly developed, non-toxic organic brakepads. The green automotive brake pads were developed from wastes Thais Coronata seashell reinforcement materials. The energy-dispersive X-ray spectrometer (EDX) was used to determine the chemical composition of the developed samples. Similar analyses were conducted on two commercial (control) samples for comparative purposes. EDX analysis showed the presence of toxic heavy metals (7 - 40%Sb, 6.44 -12.88%Ti) in the commercial (control) samples, unlike the green brake pad samples. The friction coefficient of the developed sample was obtained to be 0.584 while the commercial samples were 0.106 and 0.196. The tribological results show that the developed samples can maintain a superior frictional performance compared to the control samples and can be installed on heavy-duty automobiles. Optical microscopy results for samples of different particle sizes show that the wear depth increases with increase in the particle size of the reinforcement materials. Also, the presence of wear debris, friction films, and plateaus was more evident on the deformed surfaces of the commercial samples than on the deformed surfaces of the developed brake pad samples. [ABSTRACT FROM AUTHOR]

Powder bed fusion laser beam, as one of the most promising forming technologies, offers unmatched benefits over traditional processing, particularly in the production of Ti–6Al–4V. The influence of laser line energy density (LLED) on the forming surface, phase composition, micro-hardness, tensile characteristics and wear resistance of Ti–6Al–4V alloy were explored to disclose the evolution of mechanical and tribological properties. According to the findings, the LLED causes 'depressions' and 'highlands' between nearby scanning tracks. The phase composition did not alter appreciably as LLED increased. Micro-hardness and tensile characteristics increased initially, then declined, and the value of maximum micro-hardness and ultimate tensile strength were 388.17 HV0.2 and 1197.5 MPa, respectively. Furthermore, when the LLED is 0.24 J mm–1, the wear resistance is optimal under the aviation lubricant medium, with an average friction coefficient of 0.1505 and volume wear rate of 6.95∗10−8 mm2∗N−1, and a wear mechanism of mild furrow wear and adhesion wear. [ABSTRACT FROM AUTHOR]

The characteristics of multi-impurities and high-flow velocity in the marine environment can easily cause wear and tear of the surface coating of marine equipment, affecting the reliability and service life of the equipment. In this paper, silicon dioxide (SiO2) hybrid multi-walled carbon nanotubes (MWCNTs) composites were obtained by sol-gel method, and SiO2-MWCNTs acrylic silicone resin composite coatings were prepared. The results showed that SiO2-MWCNTs had good dispersion in acrylic silicone resin, and the lower surface energy could be found in the composite coating with 1.0wt.% hybrid material, with an average contact angle of 107.68°, the impact resistance reached 70 cm·2000 g and the interfacial bonding strength reached 3.29 MPa. The hardness and tribological properties of the composite coating with 2.0wt.% hybrid material were the highest, with the hardness reached 17.7 HV0.05, the wear volume and wear rate were 2.99 × 10− 3 mm3 and 0.12 mm3 N− 1 m− 1 respectively, which were 77.1% and 77.8% higher than those of pure acrylic silicone resin coating. This was mainly attributed to the effect of hybrid MWCNTs bridging to change the direction of crack, uniform distribution of reinforcement phase could formed a larger area of lubrication layer and reduced the friction coefficient and wear rate. In conclusion, the use of SiO2-MWCNTs could effectively improve the mechanical and tribological properties of silicone acrylate resin. [ABSTRACT FROM AUTHOR]

In this research work, fabrication of Al alloy metal matrix composites (MMCs) reinforced with electroless Ni-P-coated Al2O3 is carried out using the stir-squeeze casting method. Scrap Al alloy wheels as matrix materials and Al2O3 particles as reinforcements are used to develop the MMCs. The Ni-P coating on Al2O3 particles is carried out using an electroless process to improve mechanical and tribological properties by increasing the bonding strength between the ceramic particles and the matrix material. A pre-treatment process on Al2O3 particles is done before the electroless Ni-P coating. To analyse the properties, the composites are fabricated in three different variations, i.e. as-cast scrap Al alloy, scrap Al alloy with uncoated Al2O3 (5 wt%), and scrap Al alloy with coated Al2O3 (5 wt%). Metallurgical properties are analysed using an optical microscope (OM), scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDAX), and X-ray diffraction (XRD). The test results show that the porosity is reduced by 15.45% in a composite reinforced with coated Al2O3 compared to the as-cast scrap Al alloy. Also, the mechanical properties such as hardness, tensile strength, and impact strength are improved significantly by 15.2, 23, and 31.25%, respectively. Reduction of 31.47% in specific wear rate and 7.34% in coefficient of friction are achieved in the composite reinforced with coated Al2O3 particles compared to the as-cast scrap Al alloy. The compressive strength is decreased significantly with the addition of uncoated Al2O3 particles. After the addition of coated Al2O3, the compressive strength of the composite is increased compared with the uncoated Al2O3-reinforced composite. [ABSTRACT FROM AUTHOR]

In order to improve the wear resistance of WNiCoFe alloy for cutting tools, WNiCoFe alloy powder is prepared by multiple metals electrolysis, alloy powder and its sintered morphology is observed and phase is analyzed using X-ray diffractometer and scanning electron microscope (SEM), the effect of sintering temperature on its physical mechanics and friction properties was studied. The results show that the prepared WNiCoFe alloy powder is alloyed to some extent, irregular and finer particle size, the diffraction peaks of Co 3 Fe 7 and Fe 19 Ni are formed in addition to the elemental Fe; the maximum hardness of the sintered is 107.6HRB, the maximum bending strength at three points is 1638.3 mpa, the maximum density is 96.2%, and wear loss is 0.498–0.555 g when WNiCoFe alloy powder is sintered at 800 ∘ C. Diamond tools are made with WNiCoFe alloy powder as the main matrix composition, and cut hard stone, cutting velocity is 8.6 m 2 /h and life is 11.3 m 2 /m, which has a good comprehensive performance. [ABSTRACT FROM AUTHOR]

Al-xNi-yCeO 2 (x = 6, 10, 15, 20 and y = 0, 5, 10 wt%) composites were produced by a powder metallurgical production route. Powder mixtures of Al, Ni and CeO 2 were fabricated via mechanical alloying (MA) for 4 h in a Spex-type high-energy ball mill. Both the mechanically alloyed (MAed) and non-MAed (as-blended mixtures) powders were pre-compacted in a hydraulic press under 650 MPa and then pressurelessly consolidated at 630 °C for 2 h under an inert atmosphere. The effects of MA process and the amounts of Ni and CeO 2 on the microstructural, mechanical and tribological properties of the sintered composites were determined. Based on the SEM and XRD investigations, the MAed powders illustrated a homogenous structure, comprising flaky particles with smaller crystallite sizes and greater lattice strain. According to the XRD analysis, Ni formed Al–Ni intermetallic compounds in the matrix of sintered composites that act as secondary reinforcement phases. The SEM observations conducted on the MAed samples demonstrated more uniformly and finely distributed Al 3 Ni and CeO 2 phases in the microstructure of the MAed samples, unlike the non-MAed ones. The hardness values of sintered composites increased due to the MA process and increasing Ni and CeO 2 amounts, and the hardness value of the MAed Al20Ni–10CeO 2 sample reached 179 HV. The ultimate compressive strength and failure strain of the MAed Al6Ni–10CeO 2 sample were 441 MPa and 11.3%. In the Al20Ni–10CeO 2 sample, the compressive strength and failure strain were 391 MPa and 5.5%, respectively. Additionally, the reciprocating wear test results illustrated that both wear resistance and hardness values of the composites increased as the amounts of Ni and CeO 2 increased, and the Al20Ni–10CeO 2 sample exhibited the highest wear resistance as 0.175 × 10-3 mm3/Nm. [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]

The WSx/Fe/a-C/Fe multi-layer films with various Fe layer thicknesses were prepared by using magnetron sputtering and alternate deposition of WSx, Fe, and a-C layers on the silicon substrates. The morphology, micro-structure, and composition of the films were characterized by scanning electron microscope, energy dispersive spectroscopy, electron probe micro-analyzer, X-ray diffraction, and X-ray photoelectron spectroscopy. The mechanical and tribological properties of the fabricated films were evaluated by using nano-indenter, film stress tester, scratch tester, and ball-on-disk tribotester. According to the obtained results, all the multi-layer films revealed a featureless micro-structure with a smooth and dense surface. As the thickness of Fe layer increased, the S/W ratio of the films was decreased from 1.38 to 1.16, the hardness, elastic modulus, and adhesion of the films were gradually improved. Both the steady-state friction coefficient and wear rate were declined first and, then, enhanced. The film with the Fe-layer thickness of 4 nm exhibited the highest hardness (10.6 GPa) and adhesion (38.0 N); whereas, film with the Fe-layer thickness of 2 nm showed the best tribological performance with a steady-state friction coefficient of 0.218 and wear rate of 1.63 × 10−15m3 N−1 m−1. [ABSTRACT FROM AUTHOR]

This work was performed to investigate the mechanical and tribological properties of polymethyl methacrylate (PMMA)-based bone cement strengthened by nano-alumina (Al2O3) and nano-hydroxyapatite (HA) particles. Seven cement groups with different amounts of Al2O3 (3 and 5 wt. %) and HA (5 and 10 wt. %) nano-particles were prepared and the nanoindentation and nanoscratch tests were employed to obtain the results. Substantial improvement/reduction in mechanical properties was observed for the addition of 3 wt. % of Al2O3 /5 wt. % of Al2O3 plus 10 wt. % of HA into the PMMA matrix. The additives had almost no obvious effects on the friction of PMMA (~0.3). This research revealed that only the specific weight percent of Al2O3 (here 3 wt. %), compared to other PMMA/Al2O3 and PMMA/HA/Al2O3 cement nanocomposites, had great potential as an added component in PMMA bone cement to provide a significant increase in the mechanical properties of the cement. [ABSTRACT FROM AUTHOR]

Increasing interest for industrial use of thermally sprayed coatings leads to development in most thermal spraying technologies, including atmospheric plasma spraying (APS). The latest cascaded torch SinplexPro from Oerlikon Metco incorporates the efficiency advantages of cascaded arc technology into a single-cathode spray gun. It leads to more stable plasma arc across a wide range of gas flows, mixtures and pressures and also highly increases powder throughput. Thermal sprayed molybdenum coatings are widely used for improving wear resistance and sliding properties in many mechanical applications. Results of pure molybdenum coatings sprayed with cascaded plasma torch are not yet fully investigated. In this paper, mechanical properties of atmospheric plasma sprayed molybdenum coatings on steel (S235) substrate are evaluated. Optimization of spraying parameters for spherical Mo powder sprayed by cascaded plasma torch SinplexPro is carried out and the influence on final microstructure, mechanical and tribological properties of molybdenum coatings is analysed. [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]

The purposes of the work are to fabricate novel environment-friendly water-based polyamide-imide (PAI)-graphite-LaF 3 bonded solid-lubricating coatings (BSLCs), and investigate the corresponding tribological properties and mechanisms. The experimental results reveal that the preparation of the water-based PAI-graphite-LaF 3 BSLCs has significantly reduced the usage of organic solvent. When the mass percent of nano-LaF 3 is 5 wt%, the water-based PAI-graphite-LaF 3 BSLCs exhibit superior mechanical and tribological properties, which are comparable to those of the reported organic-solvent-based BSLCs. The tribological mechanisms were systematically investigated concerning the failure mechanism, the tribological reactions and structural fluctuations of graphite. Unlabelled Image • Water-based PAI-graphite-LaF 3 coatings are green lubricating materials. • Tribological properties of water-based coatings are comparable to those of the reported organic-solvent coatings. • Tribological mechanisms of water-based coatings are systematically investigated. [ABSTRACT FROM AUTHOR]

By theory calculation, a new orthorhombic form of diamond has been proved to exist. In this work, the orthorhombic diamond is clearly observed in the multiarc ion-plated varying-C VN films and the effect of C content on the microstructure, mechanical and tribological properties of varying-C VN films were studied in detail. The C doping results in the mechanical and tribological properties' improvement, together with the decrease of surface roughness and residual stress, and with the increase of C content, the scratch-resistance and wear-resistance capacities increase. The orthorhombic diamond phase only appears in VCN film with 10.97 at.% C, leading to that this VCN film has a relative low room-temperature friction coefficient (~0.56) compared with other films (~0.70), due to the easy-shear layered atomic structure. The VCN film containing 19.14 at.% C with the highest H / E and H 3/ E 2 ratios of 0.052 and 0.091 GPa has the minimum wear rate (0.53 × 10−14 m3 N−1 m−1), 82% lower than that of VN film (2.89 × 10−14 m3 N−1 m−1), due to the valid assembly of VN, VC and amorphous C phase with perfect balance of hardness and toughness. However, against Al 2 O 3 grinding ball, the main wear mechanisms of all varying-C VN films are adhesive wear and oxidative wear. Unlabelled Image • A new orthorhombic form of diamond was synthesized successfully in experiment. • The orthorhombic diamond phase only appeared in the film with 10.97 at.% C. • Easy-shear layered atomic structure of orthorhombic diamond leads to the lowest COF. • The film with 19.14 at.% C has the best mechanical and tribological properties. • The main wear mechanisms of all films are adhesive wear and oxidative wear. [ABSTRACT FROM AUTHOR]

• Waterborne PAI-graphite coatings are green lubricating materials. • Waterborne PAI-graphite coatings exhibit superior mechanical and tribological properties. • Tribological mechanisms of waterborne coatings were systematically investigated. • Tribological properties of waterborne coatings under different experimental conditions were explored. The purpose of this work is to fabricate novel green waterborne PAI-graphite bonded solid-lubricating coatings (BSLCs) with superior mechanical and tribological properties so as to replace the reported organic-solvent BSLCs to some extent, and further investigate the lubricating mechanisms. The work indicates that, the preparation of the waterborne PAI-graphite BSLCs have greatly reduced the utilization rate of organic solvents (without the usage of organic solvent). The basic physicochemical properties of the coatings have reached the corresponding level of the organic-solvent BSLCs. When the mass ratio of waterborne PAI resin and graphite is 1.2, the waterborne graphite-based BSLCs exhibit superior mechanical and tribological properties, which are comparable to those of the reported organic-solvent BSLCs. The variation of tribological properties of the waterborne PAI-graphite coatings under diversified applied loads and reciprocating frequencies were explored systematically for the sake of the better understanding of environmental adaptability of the waterborne PAI-graphite BSLCs. [ABSTRACT FROM AUTHOR]

Alloy strengthening via introducing Ni atoms into Cu monolayer of Cu/Ta nano multilayer materials (NMMs) is used to enhance mechanical and tribological properties. Molecular dynamics simulations indicate that the introduction of solid-solution Ni atoms suppresses the dislocation multiplication and glide, leading to higher hardness, better tribological performances, and stronger deformation resistance for Cu x Ni 100−x /Ta NMMs. The deformation resistance in nanoindentation is mainly determined by hardness and interlayer interface, where the interface acts as dislocation barrier and emission source to restrain main compression stress within about three monolayers. The resistance against friction-induced deformation relies on the comprehensive properties of strengthening monolayers and alloying interfaces, which induces further removal of Ta atoms. The atom-scale insights on the NMMs strengthening and the corresponding deformation mechanism are helpful for designing new wear-resistant materials. [Display omitted] • Alloying strengthening toward enhancing mechanical and tribological properties of Cu/Ta NMM is studied by MD simulation. • Improved hardness, friction and wear properties of Cu x Ni 100−x /Ta NMMs are achieved by adding Ni into Cu layer. • The deformation behavior and mechanism during nanoindentation and nanoscratch are presented. • Deformation resistance is explored by analyzing dislocation evolution and interlayer interface action. • The wear rate of different elements changes with the Ni content. [ABSTRACT FROM AUTHOR]

Abstract: Si3N4/Ag composites were firstly prepared through SPS technology, using Si3N4 and AgNO3 as raw materials. Utilizing the coordination bonding of Ag+ ions with nitrogen atoms of Si3N4, in situ generated Ag particles about 1 μm were tightly anchored on Si3N4 surface, thereby preventing the outflow of silver during sintering process. Meanwhile, smaller silver particles about 20 nm were located at the grain boundaries of Si3N4, which effectively improved the mechanical and tribological properties of Si3N4‐based composites. Finally, the Si3N4/Ag composites reinforced by Ag particles showed a friction coefficient of 0.48 ± 0.01, wear rate of 1.79 × 10−6 mm3 N−1 m−1 and fracture toughness of 7.05 ± 0.2 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]

The interest in use of hexagonal boron nitride nanoparticles (h-BN) as reinforcement for aluminium has been growing considerably due to its self-lubricating property, thermal and chemical stability. The aluminium nanocomposites containing different wt.% of B 4 C nanoparticles and Al-B 4 C-h-BN hybrid nanocomposites are prepared using stir and ultrasound assisted casting method. The prepared hybrid and nanocomposites are characterized using X-ray diffraction, Atomic Force Microscopy, Scanning Electron Microscopy and Energy Dispersive X-ray Analysis. The mechanical properties of boron based nanoparticles dispersed hybrid and nanocomposites are evaluated using tensile, impact, and microhardness testing. The results of microstructural study reveal uniform distribution, grain refinement and low porosity in the composite specimens. The tensile test results show that there is a significant improvement in tensile strength (67%) of the hybrid nanocomposites compared to the base aluminium matrix. The nanocomposite containing 6 wt.% of B 4 C nanoparticles shows the maximum values of tensile strength and hardness compared to all other combinations of reinforcements. Hybrid combination of B 4 C (2 wt.% and 4 wt.%) and h-BN (2 wt.%) nanoparticles reinforced aluminium hybrid nanocomposites shows improvement in impact energy and elongation compared to the nanocomposites. The wear properties of the hybrid nanocomposites, containing 4 wt% B 4 C and 2 wt.% h-BN, exhibit the superior wear resistance properties compared to the unreinforced aluminium matrix and nanocomposites. [ABSTRACT FROM AUTHOR]

Comparative study of Ti-C-Ni-Fe, Ti-C-Ni-Al, and Ti-C-Ni-Al/Ti-C-Ni-Fe coatings obtained by electro-spark deposition (ESD) using TiCNi electrode, magnetron sputtering (MS) of TiCNiAl target, and a combination of these methods (MS-ESD) was carried out. The coating microstructures and elemental compositions were studied by means of X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and glow discharge optical emission spectroscopy. The materials were tested in terms of their hardness, elastic modulus, elastic recovery, crack resistance, friction coefficient, and wear resistance under sliding, impact and abrasive conditions, as well as corrosion- and oxidation resistance. The work demonstrated that the utilization of a combined two-step MS-ESD technology permits to obtain bilayers made of Ti-C-Ni-Al/Ti-C-Ni-Fe coatings with improved crack-, wear- and oxidation resistance compared with their single-layered Ti-C-Ni-Al counterparts deposited by MS, and with reduced friction coefficient and enhanced corrosion resistance compared with ESD Ti-C-Ni-Fe coatings. [ABSTRACT FROM AUTHOR]

Quaternary Cr–Mo–Si–N coatings containing various Si contents were deposited on SUS304 and Si wafers by a hybrid coating system, where cathode arc ion plating (AIP) and high power impulse magnetron sputtering (HiPIMS) power sources were applied to the Cr and MoSi targets, respectively. The effects of Si content on the microstructure, surface roughness, mechanical and tribological properties of Cr–Mo–Si–N coatings were investigated. With increasing the Si content, both number and size of the macroparticles were decreased, leading to smoother coating surface, while the crystalline size was also decreased gradually. Strong (200) plane preferred orientation was confirmed in all coatings except for the sample with relatively high Si content i.e. 16.23 at. %, which existed mainly as amorphous phase. The microstructure evolution was changed from polycrystalline to nanocomposite structure and finally to an amorphous phase structure with increase of Si content. The hardness of Cr–Mo–Si–N coatings initially increased and then decreased with increasing the Si content due to the change of microstructure. The maximum hardness was approximately 26.1 GPa at Si content of 8.15 at. %, where nanocomposite Cr–Mo–Si–N coating was obtained containing nanocrystalline Cr(Mo)N phase and amorphous Si 3 N 4 matrix. In these series of coatings, the average friction coefficient was decreased with Si addition and then rebound to nearly 0.46 when the Si content surpassed certain value. The tribological properties of the coatings were also examined and the best wear resistance performance was obtained at Si content of 8.15 at. %. [ABSTRACT FROM AUTHOR]

The NiCr-WC-Al 2 O 3 composites with the addition of graphene oxide (GO) were fabricated by powder metallurgy technique. The effects of graphene oxide on the microstructure and tribological properties of the composites from room temperature to 700 °C were investigated. The tribofilms formed on the rubbing surfaces and their effects on the tribological properties of composites at different temperatures were analyzed by SEM, XRD, and EDX. The results show that the sintered composites were mainly composed of Ni-based solid solution, Al 2 O 3 , Cr x C y and WC, the optimized amount of graphene oxide in the composites is up to 3 wt % to balance the lubricity and mechanical properties of composites. The tribological properties of composites were improved by adding graphene oxide, the friction coefficient and wear rate of composites decreases with the increasing of graphene oxide contents, especially in high temperature ranges and the composites with addition of 3 wt% graphene oxide (GO) exhibits the lowest friction coefficient (0.41) and wear rate (1.0 × 10 −5 mm 3 /Nm) at 700 °C. The tribofilms composed of new compounds Ni 2 Al 18 O 29 , NiCr 2 O 4 and NiWO 4 which formed on worn surface of the composites at high temperature is responsible for the reduction of friction and the wear rate of composites. [ABSTRACT FROM AUTHOR]

Carbon fibers (CFs) were grafted with methyl acrylic via Diels-Alder reaction at the different oil bath temperature effectively creating a carboxyl functionalized surface. The effect of grafting temperature on the surface morphology and functional groups of carbon fibers were investigated by FTIR, Raman spectroscopy, XPS and SEM respectively. The results showed that the optimal grafting temperature was 80 °C, and the relative surface coverage by carboxylic acid groups increased from an initial 5.16% up to 19.30% significantly improved the chemical activity without damaging the skin and core region of the carbon fibers. Mechanical property tests indicated that the shear and tensile strength of the sample with the grafting temperature of 80 °C (CFRP-3) increased obviously by 90.3% and 78.7%, respectively, compared with the pristine carbon fibers reinforced composite. Further, the sample CFRP-3 exhibited higher and more stable friction coefficient and improved wear resistance, while the wear rate decreased 52.7%, from 10.8 × 10 −6 to 5.1 × 10 −6 mm 3 /N m. The present work shows that grafting methyl acrylic via Diels-Alder reaction could be a highly efficient and facile method to functionalize carbon fibers for advanced composites. [ABSTRACT FROM AUTHOR]

In this research work, mechanical and tribological characteristics of ortho cresol novalac epoxy (OCNE)-based nanocomposites filled with nanoparticulates of SiC, Al2O3,and ZnO have been investigated. Also, in these investigations, the influence of wear parameters such as applied normal load, sliding velocity, filler contents, and sliding distance have been explored. The experimental plan for four factors at three levels using face centered composite design (CCD) has been employed by the response surface methodology (RSM) technique. The friction and wear tests were carried out using a pin on disc wear test apparatus under dry sliding conditions. The hardness and flexural strength of nano ortho cresol novalac epoxy composites filled with nano (SiC, Al2O3,and ZnO) particulates increases with an increase in the filler contents. Whereas, the tensile strength of these nanocomposites increases with an increase in the filler contents from 1 to 2 wt%, and with a further increase in filler contents the tensile strength decreases. The results of the study also showed that (2 wt%) filler contents bring superior mechanical and tribological properties. The lowest coefficient of friction and specific wear rate were found with nano Al2O3-filled composites. Also, the wear mechanisms of these nanocomposites were studied using a scanning electron microscope (SEM) equipped with an EDS analyzer. [ABSTRACT FROM AUTHOR]

Composite TiN-Ag films with various Ag content (Ag/(Ti + Ag)) were deposited using reactive magnetron sputtering and the influence of Ag content on the crystal structure, mechanical and tribological properties were investigated. The result showed that face-centered cubic (fcc) TiN and fcc-Ag co-existed in the films and TiN had a columnar-growth and the Ag nanoparticles embedded in the boundary of columnar crystal. The hardness of TiN-Ag films initially increased gradually and reached an optimum value, and then decreased with an increase in Ag content in the films. The maximum hardness value was 29 GPa at 0.8 at.% Ag. The addition of Ag into TiN film could enhance the fracture toughness ( K IC ) and critical load ( L C1 ) of the films because the nanoparticle Ag provides a large volume fraction of grain boundaries. As Ag was added into TiN film, the average friction coefficient decreased from 0.78 at 0 at.% Ag to 0.20 at 41.1 at.% Ag; however, the wear rate of TiN-Ag films initially decreased and then increased, after reaching the minimum value of about 1.3 × 10 −7 mm 3 /(mm.N), at 0.8 at.% Ag. [ABSTRACT FROM AUTHOR]

W-Si-N composite films were deposited on both stainless steel and silicon wafers using a reactive magnetron system. The silicon content of the film was varied to evaluate the effect of silicon on films' elemental composition, microstructure, oxidation resistance, mechanical and tribological properties. These series of test were conducted using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) analytical tools. The W-Si-N films showed a two-phase structure of solid solution face-centered cubic (fcc) W(Si)N x and an amorphous Si 3 N 4 . The thermal stability and the oxidation resistant temperature of W-Si-N films increased from about 380 °C at 0 at% Si to about 650 °C at 31.2 at% Si with the incorporation of Si into W 2 N matrix. The hardness of the films increased continuously from 26 GPa at 0 at% Si to 40 GPa at 23.5 at% Si which was due to solid strengthening and fine-grained strengthening. The silicon content affected the tribological properties of the film at room temperature but this was mainly influenced by the yield pressure, H/E ratio and elastic recovery, since lubricant tribo-film WO 3 was detected on all surfaces of the W-Si-N films. There was an initial gradual decrease in average coefficient of friction and wear rate until a minimum, but a further increase in silicon content resulted in increase in both friction coefficient and wear rates. The least coefficient of friction and wear rate values were 0.30 and 8.7 × 10 − 8 mm 3 /N·mm at 23.5 at% Si. [ABSTRACT FROM AUTHOR]

Carbon nanohoops with unique structure and potential applications have successfully attracted attention from the fields of chemistry and material science. However, synthesizing carbon nanohoops is still a great challenge. Currently, we report hydrogenated amorphous carbon films with spontaneously forming carbon nanohoops were prepared through radio frequency (R.F) magnetron sputtering deposition, and the content of carbon nanohoops in the films was adjusted by varying R.F power. Raman spectroscopy and high resolution transmission electron microscopy were used to determine the formation of carbon nanohoops. It was found that the tribological and mechanical performances of the films depended on the content of carbon nanohoops in the films. The film with the maximum relative content of carbon nanohoops exhibits a low friction coefficient (0.028) and a low wear rate (3.54 × 10 − 7 mm 3 /Nm) as well as a high elastic recovery (66%). [ABSTRACT FROM AUTHOR]

• Mechanical properties of subsurface layer of films improve with nickel content. • Nickel incorporation increases the compactness and uniformity of composite films. • Subsurface layer of composite thin film shows enhanced tribological behaviour. • Frictional behaviour rely on chemical and structural properties of composite film. • Friction coefficient of films decreases with nickel which enhances the sp2 bonding. Electrodeposited nickel- carbon (Ni-C) nanocomposite thin films are found to have varying mechanical and tribological properties. Ni-C nanocomposites thin films of varying nickel content were synthesized by a simple electrodeposition method. Annealed thin films possess a relatively hard and adherent subsurface layer. In order to have an understanding of the mechanical and tribological characteristics of the subsurface layer, the relatively soft and fragile outer layer of the thin films was removed by scraping. The sp2 and sp3 bondings of carbon atoms in the thin films were explored by Raman spectroscopy. The Fourier- transform infrared spectra of the diamond-like carbon (DLC) and Ni-C thin films also consist of sp2 and sp3 hybridized carbon bonds. Nanocrystalline nickel nanoparticles distributed in carbon matrix were observed in Transmission electron microscopy study of the films. Decrease in coefficient of friction of the films is observed with increase in nickel content in thin films having DLC structure. The highest nickel content Ni-C composite thin film shows the maximum hardness of 7.6 GPa while the amorphous DLC thin film possesses the least hardness of 2.19 GPa. The subsurface layers demonstrate a clear demarcation of mechanical properties with unmodified overlayer pointing towards an extra care must be exercised before applying these electrodeposited coating on technological appliances. [ABSTRACT FROM AUTHOR]

Hard coatings, such as nitride, carbide and diamond-like carbon (DLC), have been applied to improve the tribological resistance by forming multilayer or gradient structures. In this study, Ta/TaN/Ta(C,N)/Ta-DLC coatings in gradient content and multilayer structure with different modulation periods were prepared by high-power pulsed magnetron sputtering (HiPIMS). The effect of the modulation period on the microstructure, mechanical and tribological properties was evaluated. The average grain size of the coatings first increased from 15.2 to 17.1 nm and then decreased to 9.9 nm with decreasing modulation period from 1220 to 153 nm. Ta-DLC layer is homogeneously composed of TaC crystals and amorphous carbon. The design of the gradient structure makes the multilayer interface unclear, and the interlayer interdiffusion is obvious. The reduction of the modulation period effectively improved the adhesion strength of the multilayer coating on the substrate. The multilayer coating with a modulation period of 305 nm obtained the highest hardness of 24.5 ± 0.8 GPa and Young's modulus of 263.2 ± 16.6 GPa. Compared with single-layer TaN, Ta/TaN/Ta(C,N)/Ta-DLC multilayer gradient coating had dramatically improved tribological properties, exhibiting the lowest friction coefficient of 0.15 and the lowest wear rate of 2.47 × 10−12 m3N−1 m−1 when the modulation period is 305 nm. By combining a Ta-doped DLC layer with a low friction coefficient and a TaN layer with high hardness, the multilayer gradient coating achieved excellent mechanical and tribological properties. • Ta/TaN/Ta(C,N)/Ta-DLC multilayer gradient coating synthesized by HiPIMS • By combining TaN and DLC, a composite film with excellent mechanical and Tribological properties is obtained. • Multilayer gradient structure effectively interrupts the growth of columnar crystals and optimizes interfacial bonding. • Reducing the modulation period within a certain range improves the performance of the multilayer gradient coating. [ABSTRACT FROM AUTHOR]

Deposition of hard and adherent diamond-like carbon (DLC) coatings employing an asymmetrical bipolar pulsed-DC PECVD system and an active screen that functioned as an additional cathode is presented. This novel system represents a step forward for thin coating growth by using much lower pressure (about 0.1 Pa) in an almost collision-less regime, with higher plasma density than the conventional PECVD system. In order to overcome the low adherence of DLC coatings to 316 stainless steel substrates, a thin amorphous silicon interlayer was deposited as an interface. The interlayer was synthesized using silane as precursor gas and varying the applied DC bias voltage during deposition. The DLC coatings were produced using acetylene gas as the precursor. Both the amorphous silicon interlayers and the DLC films were analyzed according to their microstructural, mechanical, and tribological properties as a function of the applied substrate bias voltage. The film's atomic arrangements were estimated by means of Raman spectroscopy, while the hydrogen content was determined via elastic recoil detection analysis (ERDA). The nanoindentation experiments helped determine the films' hardness and other nanomechanical parameters. The friction coefficient was determined using a tribometer in unlubricated sliding friction experiments, while the adhesion of the films was determined through a classic Rockwell C indentation test. The results showed an improvement of the properties and the adherence of the DLC coatings deposited using a modified experimental setup and an amorphous silicon interlayer. The composition, microstructure, and mechanical and tribological properties of the films were dependent on the applied DC bias voltage and, consequently, on the intensity of ion bombardment during coating growth. These results suggest that a combination of a modified pulsed-DC PECVD system, the use of an active screen as an additional cathode, and acetylene as a precursor gas for growing DLC films may represent a new and useful alternative for mechanical and tribological applications. [ABSTRACT FROM AUTHOR]

The present work is focused on synthesis and determination of mechanical and tribological properties of aluminium alloy Al6061-Coconut Shell Ash (CSA) MMC synthesized by STIR CASTING - PELLET METHOD. Using this method, varied weight percentage 3%, 6%, 9%, 12% and 15% of CSA particles are successfully introduced in the aluminium alloy to produce different mixtures of composite. The characterization of the composites was carried out using scanning electron microscopy, EDAX, tensile test, hardness test and wear test. The results showed the good dispersion of CSA particles in the aluminium alloy matrix and that mechanical and tribological properties of composites are better at a lower amount of CSA reinforcement. [ABSTRACT FROM AUTHOR]

Properties of nanomaterials often differ from the ones of macrosized materials, and many of them have to be investigated. As one of the example is the formation of porous anodic metal oxides. An oxide film can be grown up on certain metals by anodization, the so-called valve metals. For each of these metals there are conditions established to enable promotion of the formation of thin, dense, barrier or porous oxide having uniform thickness at the whole surface. Among valve metals aluminum is an important case because of its ability to find diverse and important applications including architectural finishes, prevention of corrosion of automotive and aerospace structures, and electrical insulation. The porous aluminium anodic oxide (AAO) collected an enormous attention, because its pores can be used as a template for preparing various nanomaterials as nanoparticles, nanowires and nanotubes. The most widely used baths contain sulfuric acid, for particular applications oxalic or phosphoric acids are also used. It has been widely accepted mechanism that the formation of pores in anodized metal oxides is based on two continuous processes, one is oxide dissolution at the electrolyte/oxide interface and the other is oxidation of metal at the oxide/metal interface. This work presents an overview on fabrication research, understanding the formation mechanism of anodic metal oxide and the application of different sized AAO materials. [ABSTRACT FROM AUTHOR]

In a reactive direct current (DC) magnetron sputtering (MS) system, converting the cathode (target) magnetic field configuration from a balanced magnetron (BM) to an unbalanced magnetron (UBM) is an impressive strategy to enforce the energetic ion bombardment, providing sufficient activation energy for deposition of high-quality nanostructured films. In the present work, the nanostructured (grain size ˂ 100 nm) BM and UBM sputtered Niobium-doped amorphous Carbon (Nb: a-Carbon) films' microstructural , mechanical, and tribological characteristics changes were thoroughly investigated and compared. From the XRD and Raman analysis outcomes both graphite-like Carbon (GLC) and Niobium carbide (NbC) phases were detected in the BM sputtered film. However, novel cubic and hexagonal crystalline Diamond (CD) phases were successfully constructed from the UBM sputtered films besides the GLC and NbC phases. Records displayed that the change over the cathode magnetic field configuration from BM to UBM is a responsible factor for the reduction of the surface roughness (from 32 nm to 25 nm) and increment of the crystallite size (from 14 nm to 15.5 nm), hardness (from 18 GPa to 27 GPa), and elastic modulus (from 210 GPa to 425 GPa) values. On the contrary, via changing BM to UBM sputtering the films' tribological properties were negatively affected, leading to the increase of the coefficient of friction (COF) from 0.09 to 0.11 and the wear rate (W R) from 5.25 × 10−5 mm3/N.m to 9 × 10−5 mm3/N.m. The achieved results confirmed that the UBM configuration could be selected as a critical facility over the MS system that gives enough energy to arrange Carbon species in the crystalline Diamond phase at a relatively low temperature. One step further, the Ar/CH 4 ratio variation was assessed as an influential factor that leaves considerable changes over the UBM sputtered film characteristics. The results indicated that by doubling the Ar/CH 4 ratio, the nanocrystalline Diamond phases are still observable. However, this change led to the increase in surface roughness (from 25 nm to 28 nm) and crystallite sizes (NbC, from 15.5 nm to 18.6 nm, cubic Diamond, from 25.8 nm to 36 nm, and hexagonal Diamond from 18.9 nm to 21.6 nm). While the variations adversely affected the UBM sputtered films' hardness (from 27 GPa to 21 GPa) and modulus of elasticity (from 425 GPa to 330 GPa). Simultaneously, the COF and W R endured a slight increment, from 0.11 to 0.14 and 9 × 10−5 mm3/N.m to 9.8 × 10−5 mm3/N.m, respectively. [ABSTRACT FROM AUTHOR]

Amorphous hydrogenated carbon (a-C:H) films were deposited employing an asymmetrical bipolar pulsed-DC plasma enhanced chemical vapor deposition (PECVD) system and an active screen that worked as an additional cathode. The influence of the acetylene (C 2 H 2 ) precursor diluted with argon on the microstructure and the mechanical and tribological properties of a-C:H films were studied. Raman spectroscopy was used to estimate the film's atomic arrangements and the hydrogen content of the films. A profilometer was used to evaluate the total stress through measurement of the change in the substrate curvature, and nanoindentation experiments allowed the determination of the hardness and the elastic modulus of the films. The friction coefficient and the wear rates of the films were determined using a tribometer in unlubricated sliding friction experiments, while the critical load of failure was determined via a classic scratch test. In order to improve the adhesion of the a-C:H films to AISI 304 and AISI 1020 steel substrates, a thin amorphous silicon interlayer was deposited as an interface between the substrates and the films, using silane as a precursor. The results showed that the atmosphere of acetylene diluted by argon induced modifications in the properties of the a-C:H films. Hard, adherent, low-stress, and high wear resistant a-C:H films were deposited on steel substrates by means of a combination of a modified asymmetrical bipolar pulsed-DC PECVD system and acetylene–argon atmospheres. [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]

Composite Nb–V–Si–N films with various V contents (3.7–13.2 at.%) were deposited by reactive magnetron sputtering and the effects of V content on the microstructure, mechanical and tribological properties of Nb–V–Si–N films were investigated. The results revealed that a three-phase structure, consisting of face-centered cubic (fcc) Nb–V–Si–N, hexagonal close-packed (hcp) Nb–V–Si–N and amorphous Si 3 N 4 , co-exists in the Nb–V–Si–N films and the cubic phase is dominant. The hardness and critical load ( L c ) of Nb–V–Si–N films initially increased gradually and reached a summit, then decreased with the increasing V content in the films and the maximum values were 35 GPa and 9.8 N, respectively, at 6.4 at.% V. The combination of V into Nb–Si–N film led to the fracture toughness linearly increasing from 1.11 MPa·m 1/2 at 3.7 at.% V to 1.67 MPa·m 1/2 at 13.2 at.% V. At room temperature (RT), the average friction coefficient decreased from 0.80 at 3.7 at.% V to 0.55 at 13.2 at.% V for the Nb–V–Si–N films. The wear rate of Nb–V–Si–N films initially decreased and then increased after reaching a minimum value of about 6.35 × 10 − 7 mm 3 /N·mm at 6.4 at.% V. As the rise of testing temperature from 200 °C to 600 °C, the average friction coefficient of Nb–V–Si–N films decreased with the increase of the testing temperature regardless of V content. However, the wear rate gradually increased for all films. The average friction coefficient and wear rate at RT and elevated temperatures were mainly influenced by the vanadium oxides with weakly bonded lattice planes. [ABSTRACT FROM AUTHOR]

The present paper is focused on the development of hard tribological coatings with low friction coefficient (CoF) in different environments (humid air, distilled water) and at elevated temperatures. TiAlSiCN/MoSeC coatings were deposited by magnetron sputtering of four-segment targets consisting of quarter circle TiAlSiCN segments, obtained by self-propagating high-temperature synthesis, and one or two cold pressed segments made of MoSe 2 and C powders in a ratio 1:1 wt%. The structure and phase composition of coatings were investigated by means of X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, and elastic recovery. The tribological properties of coatings were investigated first at room temperature against Al 2 O 3 and WC–Co balls, after which studied in distilled water and during continuous heating in air in the temperature range of 25–400 °C against Al 2 O 3 counterpart material. To evaluate their electrochemical characteristics, the coatings were tested in 1 N H 2 SO 4 solution. The obtained results show that the coating hardness depends on the amount of MoSeC additives and decreased from 40 to 28 (one MoSeC segment) and 12 GPa (two MoSeC segments). Doping with MoSeC resulted in a significant reduction of CoF values measured in humid air (RH 60 ± 5%) from 0.8–0.9 to 0.05 and an increase of wear resistance by one or two orders of magnitude depending on counterpart material. This was attributed to the presence of MoSe 2 and free carbon-based phases in the tribological contact. The TiAlSiCN/MoSeC coating with a maximal amount of MoSeC also demonstrated superior tribological characteristics in distilled water (CoF ∼ 0.1) and at moderate temperatures up to 300 °C (CoF < 0.1). The electrochemical tests showed that, in general, doping with MoSeC did not negatively affect the coating electrochemical behavior. On the contrary, the MoSeC phase demonstrated small positive effect on the anti-corrosive properties of TiAlSiCN coatings under small polarizations. [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]

Deposition of amorphous hydrogenated carbon (a-C:H) films employing an asymmetrical bipolar pulsed-DC plasma enhanced chemical vapor deposition (PECVD) system, an active screen that worked as an additional cathode represented a step forward for thin film growth by using lower pressure and higher plasma density than the conventional PECVD system. Acetylene gas was used as a precursor. In order to overcome the low adherence of the a-C:H films on steel substrates, an amorphous silicon interlayer was deposited as an interface between the substrate and the films, using silane as a precursor. The films were analyzed according to their microstructural, mechanical, and tribological properties as a function of the substrate bias voltage. The film's atomic arrangements and the hydrogen content of the films were estimated by means of Raman spectroscopy. The total stress was evaluated through the measurement of the substrate curvature, using a profilometer, while nanoindentation experiments helped determine the films' hardness and elastic modulus. The friction coefficient and the wear rates of the films were determined using a tribometer in unlubricated sliding friction experiments, while the critical load of failure was determined by a classical scratch test. The results showed that the use of the employed experimental setup and an amorphous silicon interlayer improved the a-C:H films' deposition onto steel substrates, producing good adhesion, low compressive stress, and a high hardness. The composition, microstructure, and mechanical and tribological properties of the films were dependent on the applied bias voltage. These results suggest that a combination of a modified pulsed-DC PECVD system, the use of an active screen as a cathode, and acetylene as a precursor gas for growing a-C:H films may represent a new and useful alternative for mechanical and tribological applications. [ABSTRACT FROM AUTHOR]

Ti–Mo–Si–N films with various Si content (0–17.2 at.%) were deposited by reactive magnetron sputtering and the effects of Si content on the microstructure, mechanical and tribological properties of Ti–Mo–Si–N films were investigated. The results showed that the face-centered cubic (fcc) interstitial solid solution of Ti–Mo–Si–N was formed by dissolution of Si into Ti–Mo–N lattice with the Si content in the range of 3.1–5.0 at.%. With a further increase in Si content, the films consisted of fcc-Ti-Mo-Si-N and amorphous Si 3 N 4 phases. The hardness and fracture toughness of Ti–Mo–Si–N films first increased and then decreased with the increase of Si content and the highest values were 34.5 GPa and 2.6 MP m 1/2 , respectively, at 5.0 at.% Si. The average friction coefficient and wear rate of Ti–Mo–Si–N films first decreased and then increased with the increase of Si content and the lowest values were 0.35 and 7.8 × 10 −8 mm 3 /Nmm, respectively, at 5.0 at.% Si. [ABSTRACT FROM AUTHOR]

A self‐assembling molecule, n‐octadecane phosphate, is successfully synthesized and used to modify the surface property of carbon nanofibers (CNFs). Both untreated CNFs (CNFs(u)) and treated CNFs (CNFs(t)) are incorporated in polyimide (PI) as filler to study the interfacial­property‐determined thermal, mechanical, and tribological properties of their corresponding nanocomposites. At room temperature, the mechanical properties of PI/CNFs(t) including elongation‐to‐break, tensile strength, bending strength, and impact strength are remarkably improved by 150%, 29.4%, 26.7%, and 183%, respectively, in comparison with the PI/CNFs(u) composites. At 150 °C, the enhancement of the elongation‐to‐break reaches 250%, while the tensile and flexural‐strength enhancement reduce to 2.8% and 20.4%. In addition, the tribological properties of PI/CNFs(t) composite are also improved due to the better interfacial interaction between the filler and the matrix. Microstructure analysis of the fracture surface directly reveals the better dispersion quality of CNFs(t) in PI and superior interfacial adhesion with the introduced assembling layer. [ABSTRACT FROM AUTHOR]

Abstract: To improve the tribological performance of CrN coating, VN was introduced to form the CrN/VN multilayer structure via magnetron sputtering. The CrN/VN multilayer coatings with bilayer periods of 7, 13 and 27nm were investigated on the mechanical and tribological properties. The coatings were deposited on SUS420 and Si wafers (100) via in-line magnetron sputtering system. X-ray diffractometer, scanning electron microscopy, transmission electron microscopy and electron probe micro-analyzer were used to characterize the microstructures and chemical contents. Ball-on-disc wear test was used for tribological studies. The wear debris was analyzed by X-ray photoelectron spectroscopy. A hardness of 25.2GPa and coefficient of friction of 0.21 were achieved for multilayered coating in contrast to 16.7GPa in hardness and 0.4 in coefficient of friction for CrN coating. [Copyright &y& Elsevier]

Highlights: [•] TiN/TiCN multilayer film was conducted by application of an argon plasma process. [•] After argon plasma treatment, the film structure was changed significantly. [•] The mechanical properties of the treated film were enhanced accordingly. [•] The friction coefficient of TiN layer was reduced by argon plasma treatment. [ABSTRACT FROM AUTHOR]

Abstract: The effect of Zr and O incorporation on the structure and properties of TiC(N) coatings deposited by DC magnetron sputtering of composite TiC0.5 + xZrO2 (x =10 and 20wt.%) and (Ti,Zr)C0.5 +10%ZrO2 targets in an argon atmosphere or reactively in a gaseous mixture of Ar+N2 is presented. The structure, elemental and phase composition of the coatings were studied by means of X-ray diffraction, scanning electron microscopy, and glow discharge optical emission spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, and elastic recovery using the load–depth-sensing nanoindentation method. Tribological properties were investigated using ball-on-disk tests against cemented carbide at 25°C and alumina in the temperature range of 25–500°C. To evaluate the oxidation resistance, the coatings were annealed in air at 400, 550, and 600°C for 1h. The obtained results show that the TiZrCO(N) coatings exhibit a peak hardness versus nitrogen partial pressure. The coatings with maximum hardness tested at room temperature against WC+Co and Al2O3 counterparts showed low friction coefficients below 0.25. At higher temperatures 300–500°C, the friction coefficient against an Al2O3 ball was recorded to be 0.6. The tribological tests of the coatings demonstrated their high wear resistance at moderate temperatures 25–300°C (wear rate, k ~10−6 mm3N−1 m−1). Moreover, the coatings with high Zr content were the most wear resistant. The oxidation resistance of the Zr-doped TiCON coatings was not as high as expected and restricted by 600°C. The combination of high hardness about 40GPa with low friction coefficient and superior wear resistance makes the TiZrCON coatings promising candidates for various dry tribological applications. [Copyright &y& Elsevier]

Investigated WC-Co cermets were produced via reactive sintering. In case of reactive sintering the elemental powders of tungsten, carbon black as graphite source and cobalt at first activated throw high energy milling and then the carbide synthesis is taking place in the same cycle with liquid phase sintering of the cermets. Because there is a lack of information about the influence of alloying additives on the reactive sintered WC-Co cermets, small amount of chromium carbide or vanadium carbide was added to the powders. To investigate the influence of carbon content in initial powder mixture on the microstructure and properties of reactive sintered WC-Co cermets alloyed with Cr3C2 and VC cermets with different carbon content were produced. The hardness, transverse rupture strength and erosion resistance of alloyed WC-Co cermets depending on carbon content in initial powder mixture is exhibited. [ABSTRACT FROM AUTHOR]