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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]

An experimental study has been carried out to investigate the mechanical and tribological characteristics of chopped carbon fiber (CCF) reinforced epoxy composites filled with nano-Al2O3 particulates, as a function of fiber and filler contents. The experiments were conducted using a pin-on-disc wear test apparatus under dry sliding conditions. The coefficient of friction and specific wear rate of these composites was determined as a function of applied normal load, sliding velocity, sliding distance, and reinforcement content. The tensile, flexural, and compression strengths of ortho cresol novalac epoxy and chopped carbon fiber (OCNE/CCF) filled composites are found to be within the ranges of 48–58.54 MPa, 115–156.56 MPa, and 48–61.15 MPa. Whereas the tensile, flexural, and compression strengths of OCNE/CCF/Al2O3-filled composites are found to be within the ranges of 96–110 MPa, 176–204.66 MPa, and 72–85.65 MPa, respectively. It has been observed that the coefficient of friction decreases and specific wear rate increases with increase in the applied normal loads. Further increases in the fiber (6 wt%) and particle (3 wt%) contents in the epoxy matrix resulted in a decrease of both the mechanical and tribological properties, but remains above that of the CCF reinforced epoxy composites. The worn surfaces of composites were examined with scanning electron microscopy equipped with energy dispersion X-ray analyzer and X-ray diffraction analysis technique to investigate the wear mechanisms. [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]

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.

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]

Some research directions of formulations and technology of development for polymeric antifrictional composites (solid lubrican Fts) with increased physicomechanical tribological properties are considered. These composites are based on polytetrafluoroethylene and semi-interpenetrating polymer network (SIPN) matrices and mixed organic-inorganic fillers. Comparative analysis of qualification of materials when tested in field conditions and express testing using laboratory equipment provide a reliable screening of the service life of the materials to evaluate the performance of machines and mechanisms operating under the climatic conditions of the Russian North and the Arctic. [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]

Deformation and fracture of electroplated Au-Ni coatings subjected to tribological testing under dry conditions were studied. Wear of the coatings is shown to result from macroscopic contact interaction of the specimen with the counterbody, and from abrasive action of microasperities on the counterbody surface and wear particles. The formation mechanisms of wear particles and a transfer layer were investigated, and their contribution to wear of the electroplated Au-Ni coatings was demonstrated. The significance of shear stresses arising at the coating/sublayer interface in coating fracture was substantiated. [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]

The scratch resistance behaviour of alumina-graphene nanoplatelet (GNP) (0.5, 2 and 5 vol.-%) composites was investigated using a Rockwell indenter with normal applied loads ranging from 1 to 200 N. The alumina-GNP composites behaved differently during scratch testing depending on the normal applied load. The coefficient of friction of the composites did not change much at low normal loads but increased with increasing amount of GNP in the alumina matrix for high normal loads. The addition of GNP contributed to improved scratch resistance of alumina nanocomposites only for low loads below,97 N. This correlates with the mechanical properties of the composites. As the applied load increased, the scratch resistance of the GNP composites decreased due to the presence of weakly bonded grain boundaries in the alumina matrix, which enhanced chipping of material. [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]

Abstract: Nanocomposite coatings of CrN–WS2 were prepared at different Cr contents (approximately 8–39at%) using an unbalanced magnetron sputtering system. Structural changes in CrN–WS2 coatings with variation in Cr content were studied using X-ray diffraction. CrN–WS2 coatings displayed a dense, compact microstructure with reduced columnar growth in the field emission scanning electron microscopy data. Nanoindentation and nanoscratch data showed that CrN–WS2 coatings exhibited improved mechanical and adhesive properties, respectively. Micro-tribometer tests at a load of 2 N indicated that CrN–WS2 coatings prepared at 31at% Cr exhibited a stable friction coefficient of 0.20–0.24 even after 8h. [Copyright &y& Elsevier]

Abstract: The aim of this work was a comparative investigation of the structure and properties of Al- and Cr-doped TiSiCN coatings deposited by magnetron sputtering of composite TiAlSiCN and TiCrSiCN targets produced by self-propagating high-temperature synthesis method. Based on X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy data, the Al- and Cr-doped TiSiCN coatings possessed nanocomposite structures (Ti,Al)(C,N)/a-(Si,C) and (Ti,Cr)(C,N)/a-SiCxNy/a-C with cubic crystallites embedded in an amorphous matrix. To evaluate the thermal stability and oxidation resistance, the coatings were annealed either in vacuum at 1000, 1100, 1200, and 1300°C or in air at 1000°C for 1h. The results obtained show that the hardness of the Al-doped TiSiCN coatings increased from 41 to 46GPa, reaching maximum at 1000°C, and then slightly decreased to 38GPa at 1300°C. The Cr-doped TiSiCN coatings demonstrated high thermal stability up to 1100°C with hardness above 34GPa. Although both Al- and Cr-doped TiSiCN coatings possessed improved oxidation resistance up to 1000°C, the TiAlSiCN coatings were more oxidation resistant than their TiCrSiCN counterparts. The TiCrSiCN coatings showed better tribological characteristics both at 25 and 700°C and superior cutting performance compared with the TiAlSiCN coatings. [Copyright &y& Elsevier]

The mechanical and tribological properties of chemically modified UHMWPE are studied. X-ray diffraction analysis, IR spectroscopy, scanning differential calorimetry, and electron emission are used to study the permolecular structure and friction surface of polymers with different amounts of copolymers UHMWPE and LDPE grafted with maleic anhydride. Addition of grafted UHMWPE is shown to have no effect on the viscoelastic properties of the polymer-polymer composite, while the addition of grafted LDPE noticeably improves its performance (ductility, plasticity) while retaining its strength. Chemical modification of UHMWPE significantly improves its wear resistance (two to three times), which is due to the features of polymer crystallization and the formation of a permolecular structure. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical and tribological properties of multilayers with nanometer thickness are strongly affected by interfaces formed due to mismatch of lattice parameters. In this study, molecular dynamics (MD) simulations of nanoindentation and following nanoscratching processes are performed to investigate the mechanical and tribological properties of Ni/Al multilayers with semi-coherent interface. The results show that the indentation hardness of Ni/Al multilayers is larger than pure Ni thin film, and the significant strength of Ni/Al multilayers is caused by the semi-coherent interface which acts as a barrier to glide of dislocations during nanoindentation process. The confinement of plastic deformation by the interface during nanoscratching on Ni/Al multilayers leads to smaller friction coefficient than pure Ni thin film. Dislocation evolution, interaction between gliding dislocations and interface, variations of indentation hardness and friction coefficient are studied. [Copyright &y& Elsevier]

Abstract: A comparative investigation of the structure and properties of TiAlC(N), TiCrAlC(N), and CrAlC(N) coatings deposited by sputtering of МАХ-phase Ti2− х Cr х AlC targets (where x =0, 0.5, 1.5, and 2) in an Ar atmosphere or in a gaseous mixture of Ar+N2 is presented. The coatings were characterized in terms of their structure, elemental and phase composition, hardness, elastic modulus, elastic recovery, thermal stability, friction coefficient, wear rate, corrosion, and high-temperature oxidation resistance. The structure of the coatings was studied by means of X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, glow discharge optical emission spectroscopy, electron energy loss spectroscopy, and Raman spectroscopy. To evaluate the thermal stability and oxidation resistance, the coatings were annealed either in vacuum or in air at temperatures 600–1200 °C. The results obtained show that the TiAlCN coatings possess high hardness of 32–35 GPa, low friction coefficient against WC–Co well below 0.25, high thermal stability up to 1200 °C, and superior performance in dry milling tests against high Cr steel. Meanwhile, the coatings with high Cr content demonstrated improved oxidation resistance up to 1000 °C and superior electrochemical behavior, but their mechanical and tribological properties were deteriorated. [Copyright &y& Elsevier]

Abstract: One binary Al–40Zn and five ternary Al–40Zn–Cu alloys with different copper contents were prepared by permanent mould casting. Their microstructure and mechanical properties were investigated in as-cast state. Friction and wear properties of the ternary alloys were studied using a conforming block-on-disc type tester. The results obtained were compared with those of SAE 65 bearing bronze. The microstructure of Al–40Zn–Cu alloys consisted of aluminium-rich α dendrites surrounded by eutectoid α+η phases and θ (CuAl2) particles. Hardness of the ternary alloys increased continuously with increasing copper content, but their tensile strength decreased above 3% Cu. Friction coefficient and temperature of the Al–40Zn–Cu alloys and bronze increased in the initial period of run. This was followed by a reduction in the properties and attainment of constant levels afterwards. However, volume loss of the alloys increased rapidly at the beginning of the test run and reached almost constant levels after a sliding distance of approximately 400km. The Al–40Zn–Cu alloys were found to be much superior to the SAE 65 bronze, as far as their wear resistance is concerned. Among the alloys tested, highest strength and wear resistance were obtained with the Al–40Zn–3Cu alloy. [Copyright &y& Elsevier]

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]

Abstract: A comparative investigation of Ti–B–N, Ti–Cr–B–N, Ti–Si–B–N, and Ti–Al–Si–B–N coatings deposited by DC magnetron sputtering and ion implantation assisted magnetron sputtering of composite targets TiBN, TiCrB, TiSiB, and TiAlSiB in an Ar atmosphere or reactively in a gaseous mixture of Ar+N2 is presented. The targets were manufactured by means of a self-propagating high-temperature synthesis method. The microstructure and phase composition of coatings were studied by means of X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The films were characterized in terms of their hardness, Young’s modulus, elastic recovery, adhesion (critical load), friction and wear. The lifetime of drills coated with Ti–Cr–B–N and Ti–Si–B–N coatings as well as the productivity of the drilling process were examined. [Copyright &y& Elsevier]

Individual hard thin film materials such as TiN, SiN1.3, SiC and CNx exhibit attractive mechanical, tribological, optical and electronic properties related to their microstructure and chemical bonding. In the present work, we combine the characteristics of such materials, while systematically studying quaternary thin films prepared by plasma enhanced chemical vapor deposition (PECVD) from TiCl4/SiH4/N2/CH4 mixtures with different concentrations of CH4. Detailed structural and chemical characterizations using transmission electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and elastic recoil detection suggest formation of a TiCxNy/SiCN nanocomposite structure. Depth-sensing indentation, static indentation and curvature measurements, on samples prepared under optimal conditions, reveal a hardness of 55 GPa, reduced Young''s modulus of 302 GPa, a compressive stress of 2.0 GPa, an elastic rebound of more than 80 %, H3/Er2 coefficient of 1.8 GPa and a high toughness. The friction coefficient and the wear rate, measured against diamond, are 0.13*10-6 and 12*10-6 mm3/Nm, respectively. We compare the properties of the present nanocomposite TiCxNy/SiCN coatings with the performance of PECVD films from our earlier studies: these include TiN/SiN1.3 nanocomposites and SiCN, for which we obtained a hardness of 45 and 33 GPa, and a reduced Young''s modulus of 350 and 200 GPa, respectively. [Copyright &y& Elsevier]