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Dense (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C with up to 10 wt % SiC whisker were prepared by spark plasma sintering. The influence of SiCw on the microstructure development, mechanical and tribological properties has been investigated. Nanohardness of HEC and SiCw phases varied between 38 GPa and 40 GPa, and indentation modulus of elasticity was ∼605 GPa. The hardness of the composites increased from 22 GPa to 27 GPa and indentation fracture resistance from 3.55 MPa m1/2 to 4.59 MPa m1/2 with increasing SiCw content. The main toughening mechanisms were crack deflection, crack branching, and crack bridging. The system HEC +5 wt% of SiCw was found to possess the highest bending strength of 623 ± 25 MPa. The composites exhibited similar coefficients of frictions with around 0.3 and wear rates approximately 1.50 × 10−6 mm3/N⋅m at 5 N and 2.66 × 10−6 mm3/N⋅m at 25 N with positive influence of SiC phase on the wear mechanisms.

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]

Using the method of high-frequency ion-plasma sputtering (magnetron high-frequency deposition under conditions of ion-plasma assisted using a gas (argon) plasma generator «PINK») on the surface of a high-entropy CoFeCrMnNi alloy of non-equiatomic composition. Boron-containing coatings of the elemental composition Al – Mg – B and Mg – Ti – B with a thickness of 3 μm are formed. Using transmission electron diffraction microscopy, it was found that the coatings are amorphous-crystalline, i.e. contain nanosized 1.5-2 nm islands of the crystalline phase located in an amorphous matrix. It is shown that the coating deposition is accompanied by the formation in the substrate layer (high-entropy alloy) adjacent to the coating of a nanocrystalline structure with a crystallite size of 25-40 nm. At the boundaries of the crystallites, particles of iron boride of the FeB and Fe3B compositions are revealed, which indicate the penetration of boron into the substrate. The particle size of iron boride is 5-8 nm.

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]

Deposition of (Ti-Al)N/MoN multilayered coatings was carried out through a cathodic ion-plating system in an argon and then nitrogen atmosphere. Bilayer thickness (Λ) of all the samples were achieved, from 22 to 104 nm, by organizing substrate holder rotational speed (SRS). To obtain the optimum properties of the (Ti-Al)N/MoN coatings, the Ti and Al ratio was maintained at a level of 1:1. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were utilized to analyze the crystal structure and morphology of the coatings. Mechanical and tribological properties were examined by nanohardness and atomic force microscopy (AFM). The preferred orientation of the (Ti-Al)N/MoN nanoscale multilayer films was TiAlN (200) and MoN (200), which had face centered cubic (fcc) and hexagonal structures, respectively. The hardness increased with the decrease in Λ (104 nm to 26 nm), and then it increased. The highest hardness of 37 GPa was revealed at Λ = 26 nm, whereas the least wear rate of 8.09 × 10−7 mm3/N.m was attained at Λ = 22 nm. Wear rate, roughness, and coefficient of friction were decreased with decreasing bilayer period. EDS results showed that Al and Ti contents were almost the same in all samples, as per design of the experiment. [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]

A direct current magnetron sputtering (DCMS) system at room temperature was applied to deposit the Ti/TiN/TiCN films. In order to research the effect of the microstructure of the TiN/TiCN layer on the Ti/TiN/TiCN films, the deposition time ratio of the TiN/TiCN layer ranged from 28.57 to 200%, and the whole deposition time of the films and the deposition time of Ti layer were constant. In this work, the relationship between structure and mechanical properties of films were investigated. The research results showed that the composition and structure of the films only slightly changed, while the crystalline orientation of the TiCN layer was of significant variation with the deposition time of the TiN layer. It is shown that the adhesion strength and internal stresses were 18.6 ± 1.5 N and 140 MPa when the deposition time ratio was 50%. By adjusting the deposition time ratio, the films displayed significant improvement in tribological behaviors. The coefficients of friction (COF) for the films deposited under deposition time ratio of 50% were about only 0.139 when the value of COF was stabilized. This work can provide a good wear-resisting film prepared approach at room temperature. [ABSTRACT FROM AUTHOR]

Mechanical and tribological properties of nylon 6 and nylon 6/h-BN composites were investigated in this paper. Tensile, hardness, and impact tests were carried out for mechanical properties, while wear tests on pin-on-disc were carried out for tribological properties identification. Abrasion resistance tests were carried out on the TABER apparatus to analyze the abrasive wear of materials. SEM, XRD, and TGA were used to characterize the materials and to understand the distinctive features of nylon 6 and nylon 6/h-BN composites. Experimental results show that the mechanical properties and tribological behavior of nylon 6 got enhanced by the h-BN fillers. Tensile strength and modulus of elasticity were enhanced by 15.2% and 64.5%, respectively, while hardness and impact strength were enhanced by 3.45% and 6%, respectively. COF and wear rate of composites decreased up to 4 wt% filler reinforcement due to smooth transfer film formation. Coefficient of friction (COF) and wear resistance were improved by 10–15% and 8–10%, respectively, at various testing conditions. h-BN reinforcement in the matrix resulted in more weight loss due to abrasion and it reduced the abrasion resistance of nylon 6 by 5.5 times. Thermal stability was slightly increased, and crystallinity was little affected by the h-BN fillers.

A direct current magnetron sputtering (DCMS) system at room temperature was applied to deposit the Ti/TiN/TiCN films. In order to research the effect of the microstructure of the TiN/TiCN layer on the Ti/TiN/TiCN films, the deposition time ratio of the TiN/TiCN layer ranged from 28.57 to 200%, and the whole deposition time of the films and the deposition time of Ti layer were constant. In this work, the relationship between structure and mechanical properties of films were investigated. The research results showed that the composition and structure of the films only slightly changed, while the crystalline orientation of the TiCN layer was of significant variation with the deposition time of the TiN layer. It is shown that the adhesion strength and internal stresses were 18.6 ± 1.5 N and 140 MPa when the deposition time ratio was 50%. By adjusting the deposition time ratio, the films displayed significant improvement in tribological behaviors. The coefficients of friction (COF) for the films deposited under deposition time ratio of 50% were about only 0.139 when the value of COF was stabilized. This work can provide a good wear-resisting film prepared approach at room temperature.

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]

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]

In this work, two copper metal matrix composites (MMCs) reinforced with 20 wt.% of Ti(C,N) or Ti2AlN particles were studied. The reinforcement particles were synthesized by flash sintering under 2 bar nitrogen atmosphere causing an SHS reaction ignited by electrical current. This reaction led to produce TiC0.7N0.3 solid solution for the MMC1 reinforcement and Ti2AlN, TiN, and Ti3Al titanium aluminide for the MMC2 reinforcement. Both MMCs were densified by liquid phase sintering. The structural characterization was performed by XRD analysis while the morphology and chemical element distribution of both MMCs were analyzed by SEM and EDS. The structure of the two MMCs was relatively dense and showed good wettability. The mechanical and tribological behavior of MMCs evaluated by nanoindentation and wear testing reveals that the addition of 20 wt.% of reinforcement considerably improves the properties of copper matrix. Indeed, the MMC1 proved to be 3 times harder and 10 times more wear-resistant than the MMC2 composite. [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 coatings ZrB2 and Zr-B-N were deposited by magnetron sputtering of ZrB2 target in Ar and Ar–15%N2 atmospheres. The structure and properties of the coatings were investigated via scanning and transmission electron microscopy, energy dispersion analysis, optical profilometry, glowing discharge optical emission spectroscopy and X-ray diffraction analysis. Mechanical and tribological properties of the coatings were investigated using nanoindentation, “pin-on-disc” tribological testing and “ball-on-plate” impact testing. Free corrosion potential and corrosion current density were measured by electrochemical testing in 1 N H2SO4 and 3.5%NaCl solutions. The oxidation resistance of the coatings was investigated in the 600–800 °C temperature interval. The coatings deposited in Ar contained 4–11 nm grains of the h-ZrB2 phase along with free boron. Nitrogen-containing coatings consisted of finer crystals (1–4 nm) of h-ZrB2, separated by interlayers of amorphous a-BN. Both types of coatings featured hardness of 22–23 GPa; however, the introduction of nitrogen decreased the coating’s elastic modulus from 342 to 266 GPa and increased the elastic recovery from 62 to 72%, which enhanced the wear resistance of the coatings. N-doped coatings demonstrated a relatively low friction coefficient of 0.4 and a specific wear rate of ~1.3 × 10−6 mm3N−1m−1. Electrochemical investigations revealed that the introduction of nitrogen into the coatings resulted in the decrease of corrosion current density in 3.5% NaCl and 1 N H2SO4 solution up to 3.5 and 5 times, correspondingly. The superior corrosion resistance of Zr-B-N coatings was related to the finer grains size and increased volume of the BN phase. The samples ZrB2 and Zr-B-N resisted oxidation at 600 °C. N-free coatings resisted oxidation (up to 800 °C) and the diffusion of metallic elements from the substrate better. In contrast, Zr-B-N coatings experienced total oxidation and formed loose oxide layers, which could be easily removed from the substrate.

Single-component coatings of Cu and C and coatings in the Cu–C system with different carbon contents have been obtained by the magnetron sputtering method. The structure of coatings was investigated by the following techniques: scanning electron microscopy, energy-dispersive and X-ray diffraction analysis, Raman spectroscopy, and radio-frequency glow-discharge spectroscopy. The mechanical and tribological properties have been determined using the nanoindentation and testing by the "rod–disk" scheme. It has been established that the introduction of carbon into the composition of copper-based coatings is accompanied by an increase in the density of the structure and by the reduction of the crystallite size from 35 to 21 nm. It has been revealed that the characteristics of the Cu–C coatings exceeded those of the Cu coatings. The Cu‒C coatings obtained using the best regimes had a hardness of more than 1.5 GPa and coefficient of friction ~0.19. [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: 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]

The use of nanostructured materials and activated methods of surface engineering for creation of modern technics objects. The principles of control of forming rocesses of structure and phase in the materials and coatings in the presence of nanosized modifying particles are described. The scientific and technological bases of the formation of structure and properties of surface layers under the action of thermal, mechanical, chemical, electrophysical factors in the realization of various surface engineering methods (electrochemical deposition, gas-thermal spraying, microarc oxidation, friction plating, ion beam implantation, tribomechanical modification) are shown. The examples of application of the developed nanostructural materials and coatings with high physico-mechanical and tribological properties for production of friction assemblies of various technical objects are shown.

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.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1347

The present study compares the effect of SiC reinforcement on densification and properties of supersolidus liquid phase sintered 6711Al-SiC composites. The prealloyed 6711 powders were mixed with SiC ranging from 5 to 20 vol.%, compacted at 400 MPa and sintered at 630ºC under vacuum. It was shown that better densification, yield strength, wear and corrosion resistance were achieved up to 10 vol.% due to uniform distribution of SiC particles throughout matrix. Beyond 10 vol.%, SiC resulted in clustering and had detrimental effect on densification and mechanical properties. Age hardening of 6711-10SiC composites led to improvement in mechanical properties.

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]

Abstract: Films of Ti–Ca–P–C–O–(N), Ti–Ca–C–O–(N) and Ti–Zr–C–O–(N) were deposited by DC magnetron sputtering or ion implantation-assisted magnetron sputtering of composite targets TiC0.5+10%Ca10(PO4)6(OH)2, TiC0.5+20%(CaO+TiO2) and TiC0.5+10%ZrO2 in an Ar atmosphere or reactively in a gaseous mixture of Ar+14%N2. The microstructure, elemental and phase composition of films were studied by means of X-ray diffraction, transmission electron microscopy, scanning force microscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. The films were characterized in terms of their hardness, Young''s modulus, elastic recovery, adhesion strength, and friction and wear both in air and under physiological solution. Particular attention was paid to the analysis of deformation and fracture for various film/substrate systems during scratch testing. The biocompatibility of the films was evaluated by both in vitro and in vivo experiments. In vitro studies involved the investigation of adhesion, spreading, and proliferation of MC3T3-E1 osteoblasts and IAR-2 epithelial cells, morphometric analysis, actin cytoskeleton, focal contacts staining, alkaline phosphatase activity and von Kossa staining of osteoblastic culture. Cell culture experiments demonstrated an increase of osteoblastic proliferation on Ca- and P-incorporated films. In vivo studies were fulfilled by subcutaneous implantation of Teflon plates coated with the tested films in mice and analysis of the population of adherent cells on their surfaces. The results obtained show that multicomponent nanostructured Ti–(Ca, Zr)–(C, N, O, P) films possess a combination of high hardness, wear resistance and adhesion strength, reduced Young''s modulus, low friction coefficient and high biocompatibility. [Copyright &y& Elsevier]

Hard amorphous DLC films were deposited onto ultra high molecular weight polyethylene (UHMWPE) and metallic substrates (Ti, Co–Cr–Mo, stainless steel 138F) used as biomaterials by pulsed arc discharge using a carbon source accelerator in 2×10-4 Pa vacuum. DLC films were analyzed by Auger electron spectroscopy, electron energy loss spectroscopy, nanoindentation, scratch test and Rockwell indentation. Dry friction coefficient of films deposited on UHMWPE and stainless steel were also investigated. The results obtained are discussed with literature data. [Copyright &y& Elsevier]

TiN coating was deposited on high-speed steel, cemented carbide and TiCN-based cermets using arc evaporation. The variation of substrates was to evaluate the effect of tool materials on the coating's microstructure, composition, hardness, adhesion and tribological properties. The TiN coating on all tool materials had a strong preferred TiN (111) orientation. The TiN coating on high-speed steel grew so fast in the vertical direction that the columnar crystal structure was noticeable. The columnar structure of TiN coating on TiCN-based cermets weakened for the reduced vertical growth rate. The Ti/N atomic content ratio of the TiN coating on high-speed steel was 0.84, and some N atoms formed an interstitial solid solution, which contributed to the increased hardness of the coating. However, the Ti/N atomic content ratio of TiN coating on TiCN-based cermets increased to 1.04. Due to the low residual stress, the adhesion of TiN coating on TiCN-based cermets and cemented carbide was noticeably higher than that of coating on high-speed steel. The wear mechanism of TiN coatings on all tool materials tested against with steel balls was mainly abrasive wear. An iron oxide film appeared on the coated TiCN-based sample, which directly caused the friction coefficient to decrease from 0.8 to 0.6. Therefore, the TiN coating on TiCN-based cermets had the best wear resistance. • Microstructure and properties of TiN coating were affected by the tool materials. • TiN coating on high-speed steel had high hardness and H 3/ E *2 ratio. • TiN coating on cemented carbide and TiCN-based cermets had high adhesion. • Iron oxide formed in the wear process exhibited a good anti-friction effect. • TiN coating on TiCN-based cermets possessed the best wear resistance. [ABSTRACT FROM AUTHOR]

• The effect of sintering temperature on the mechanical and friction properties of GNPs/TC21 composites were investigated. • A model of the relationship between the interfacial evolution of composites and sintering temperature was established. • The strengthening mechanism of GNPs/TC21 composites was revealed using TEM microstructural analysis. Schematic diagram of microstructure evolution with increasing sintering temperature. (a)Spherical particle sintering model, (b) TC21 spherical particle bonding at lowtemperature sintering, (c) interfacial bonding at medium temperature sintering,(d) interfacial bonding at high temperature sintering. Schematic illustration of the strengthening mechanism of TiC@GNPs bands and TiC particles/plates. (a) Synergistic strengthening mechanism of TiC@GNPs bands and TiC particles/plates, (b) Strengthening mechanism of TiC particles/plates [Display omitted] Graphene nanoplates (GNPs) have been adopted in titanium matrix composite manufacturing and design due to its superior mechanical properties. In this study, Graphene nanoplates reinforced Ti-6Al-2Sn-2Zr-3Mo-1Cr-2Nb-Si alloys (named as GNPs/TC21 composites) were prepared by using spark plasma sintering (SPS), and the effects of sintering temperature on the microstructure, mechanical and wear properties of GNPs/TC21 composites were systematically investigated. The results indicate that the sintering temperatures show a great influence on the interfacial structure. With the increase of sintering temperature from 850 °C to 1050 °C, the interfacial microstructures exhibit three morphographies: (1) The original TC21 particles coated with GNPs (850 °C); (2) A special TiC@GNPs band (900 °C−1000 °C); (3) A discontinuous network structure wrapped by TiC particles/plates (1050 °C). Mechanical and tribological properties of the GNPs/TC21 composites were investigated at room temperature. The optimal SPS temperature was 1000 °C, at which the GNPs/TC21 composites show the best comprehensive mechanical properties i.e. the ultimate tensile strength and yield strength are 1167 MPa and 1041 MPa, the friction coefficient is 0.16275 and the wear loss is 0.0179 g. The improvement of mechanical properties can be attributed to the synergistic strengthening of the load transfer effect of TiC@GNPs bands and the pinning effect of TiC particles/plates. The excellent wear resistance is mainly attributed to the pinning of TiC particles on the surrounding metal matrix and the strengthening and lubrication of GNPs. [ABSTRACT FROM AUTHOR]

The coatings ZrB2 and Zr-B-N were deposited by magnetron sputtering of ZrB2 target in Ar and Ar–15%N2 atmospheres. The structure and properties of the coatings were investigated via scanning and transmission electron microscopy, energy dispersion analysis, optical profilometry, glowing discharge optical emission spectroscopy and X-ray diffraction analysis. Mechanical and tribological properties of the coatings were investigated using nanoindentation, "pin-on-disc" tribological testing and "ball-on-plate" impact testing. Free corrosion potential and corrosion current density were measured by electrochemical testing in 1 N H2SO4 and 3.5%NaCl solutions. The oxidation resistance of the coatings was investigated in the 600–800 °C temperature interval. The coatings deposited in Ar contained 4–11 nm grains of the h-ZrB2 phase along with free boron. Nitrogen-containing coatings consisted of finer crystals (1–4 nm) of h-ZrB2, separated by interlayers of amorphous a-BN. Both types of coatings featured hardness of 22–23 GPa; however, the introduction of nitrogen decreased the coating's elastic modulus from 342 to 266 GPa and increased the elastic recovery from 62 to 72%, which enhanced the wear resistance of the coatings. N-doped coatings demonstrated a relatively low friction coefficient of 0.4 and a specific wear rate of ~1.3 × 10−6 mm3N−1m−1. Electrochemical investigations revealed that the introduction of nitrogen into the coatings resulted in the decrease of corrosion current density in 3.5% NaCl and 1 N H2SO4 solution up to 3.5 and 5 times, correspondingly. The superior corrosion resistance of Zr-B-N coatings was related to the finer grains size and increased volume of the BN phase. The samples ZrB2 and Zr-B-N resisted oxidation at 600 °C. N-free coatings resisted oxidation (up to 800 °C) and the diffusion of metallic elements from the substrate better. In contrast, Zr-B-N coatings experienced total oxidation and formed loose oxide layers, which could be easily removed from the substrate. [ABSTRACT FROM AUTHOR]

The spontaneously self-organizing multilayered graphite-like carbon (denoted as GLC) /TiC films with various bilayer periods in the range of 13.3–17.5 nm were deposited on silicon and 1Cr18Mn8Ni5N stainless steel substrates using closed field magnetron sputtering deposition facility. The microstructures and chemical compositions of the prepared multilayered films were characterized by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy respectively. The self-organizing multilayered structures in all of the films consisted of titanium carbide layers and sp2-rich carbon layers periodically alternate arrangement. The TiC contents and bilayer periods of the multilayered films can be controlled by means of adjusting of sputtering current of graphite target. Furthermore, the mechanical and tribological performances of the prepared films were appraised by nano-indentor, scratch measures, and ball-on-plate tribometer respectively. The results indicated that multilayer structure endowed the as-deposited TiC/GLC films outstanding mechanical and tribological properties, especially the multilayer film with 15.9 nm bilayer period deposited at 10 A sputtering current showed the excellent adhesion strength and hardness; Simultaneously it also exhibited the lowest average friction coefficient in the humid environment owing to its high content of sp2 hybrid carbon. [ABSTRACT FROM AUTHOR]

Coatings in a Zr-Mo-Si-B-N system were deposited by the magnetron sputtering of ZrB2-MoSi2 targets in argon and nitrogen. The structure of the coatings was investigated using scanning electron microscopy, X-ray diffraction, energy-dispersive spectroscopy, and glow-discharge optical emission spectroscopy. Mechanical and tribological properties were measured using nanoindentation and pin-on-disc testing. Oxidation resistance and oxidation kinetics were estimated via annealing in air at 1000–1500 °C and precision weight measurements. We found that the coatings deposited in Ar demonstrate a superior combination of properties, including hardness of 36 GPa, elastic recovery of 84%, a friction coefficient of 0.6, and oxidation resistance at temperatures up to 1200 °C. High oxidation resistance is realized due to the formation of the protective (SiO2 + ZrO2)/SiO2 oxide layer, which inhibits the diffusion of oxygen into the coating. [ABSTRACT FROM AUTHOR]

• Technological advancements in functionally graded materials. • Comparison of various homogenization schemes. • Review on analysis of functionally graded structures. • Suggested future scope in the analysis of functionally graded structures. • Review on various fabrication methods of functionally graded materials along their mechanical and tribological performance. This paper discourses an overview of the recent advancements in functionally graded materials (FGMs) research. The paper also disseminates on the key researches that are carried out in the scientific community on the development of manufacturing and modelling of functionally graded materials. The rationale of the current work is to emphasize the selection of materials, processing techniques and analytical modelling and applications of FGMs. Alongside, challenges involved in developing these materials towards various aspects of scientific and technological fields will be addressed. [ABSTRACT FROM AUTHOR]

As part of the tests, a two-phase NiAl/Ni3Al alloy and a composite based on this alloy with 4 vol% addition of TiB2 were produced by the reactive FAST/SPS (Field Assisted Sintering Technology/Spark Plasma Sintering) sintering method. The sintering process was carried out at 1273 K for 30 s under an argon atmosphere. The effect of reactive SPS on the density, microstructure, and mechanical and tribological properties of a dual-phase Ni-Al intermetallic compound and Ni-Al-TiB2 composite was investigated. Products obtained were characterized by a high degree of sintering (over 99% of the theoretical density). The microstructure of sinters was characterized by a large diversity, mainly in regard to the structure of the dual-phase alloy (matrix). Compression tests showed satisfactory plastic properties of the manufactured materials, especially at high temperature (1073 K). For both materials at room temperature, the compressive strength was over 3 GPa. The stress–strain curves were observed to assume a different course for the matrix material and composite material, including differences in the maximum plastic flow stress depending on the test temperature. The brittle-to-ductile transition temperature was determined to be above 873 K. The research has revealed differences in the physical, mechanical and tribological properties of the produced sinters. However, the differences favourable for the composite were mostly the result of the addition of TiB2 ceramic particles uniformly distributed on grain boundaries. [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]

Since obtaining a highly oriented structure based on a large-scale commercial ultra-high molecular weight polyethylene (UHMWPE) is considered very difficult due to its high molecular weight and melting index, modifying the structure of these cheap commercial UHMWPE brands into a supra-molecular structure with fiber-forming properties by adding a small amount of polyethylene wax (PE-wax) will provide the possibility to obtain highly oriented UHMWPE products with enhanced mechanical and tribological properties. In this work, highly oriented UHMWPE/PE-wax films were prepared. The PE-wax affected the UHMWPE as an intermolecular lubricant. The obtained lamellar structure of the UHMWPE/PE-wax composites had a better processability. The UHMWPE and UHMWPE/PE-wax structures for the xerogels and the films were studied by using differential scanning calorimetry and scanning electron microscopy. The PE-wax presence enhanced the mechanical properties of the UHMWPE/PE-wax films to a high degree. The highest average value of the tensile strength was 1320 MPa (an increase of 78%) obtained by adding a PE-wax content of 1.0 wt.%, and the highest average value of the Young's modulus was 56.8 GPa (an increase of 71%) obtained by adding a PE-wax content of 2.0 wt.%. The addition of the PE-wax increased the work of fracture values of the UHMWPE/PE-wax films up to 233%. The formation of the cavities was observed in the virgin UHMWPE films more than in the UHMWPE/PE-wax films, and the whitening of the oriented films was related to the crystallization process more than to the cavitation phenomenon. The coefficient of friction of the oriented UHMWPE/PE-wax films improved by 33% in comparison with the isotropic UHMWPE, and by 7% in comparison with the oriented virgin UHMWPE films. [ABSTRACT FROM AUTHOR]