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

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]

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

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

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

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]

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

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]

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]

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]

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.

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]

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]

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: 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]

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]

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]

Based on the advantage of rapidly fabricating parts with complex geometric shapes, selective laser melting (SLM), an additive manufacturing technology, is utilized to process 3 wt.% TiC/Ti6Al4V composites. A TiC-reinforced Ti6Al4V composite with directionally grown unique microstructures is prepared by SLM. The effect of the laser power and scanning speed on the relative density, constitutional phases, and microstructure features is investigated systematically. The microstructure evolution mechanism is clarified. Moreover, the influence of the unique microstructure on the mechanical and tribological properties is investigated. The results indicate that the relative density of the SLM-processed TiC/Ti6Al4V composite can reach 98.7%. Because of the special processing technology used in SLM, unique nanoscale lamellar and needle-like eutectic TiC reinforcement phases, which have never been observed in TiC/Ti6Al4V composites prepared by other flexible laser additive manufacturing technologies, are formed. Furthermore, the composites are dominated by extremely small grains. The nanoscale eutectic TiC and refined grains significantly enhance the hardness and tensile strength of the composites. The microhardness and ultimate tensile strength reach 487 HV and 1565 MPa, respectively. More importantly, the nanoscale reinforcement promotes the migration of C and the formation of a dense solid lubricant film during friction, leading to excellent tribological properties at different applied loads. As the applied load increases from 5 N to 15 N, due to the enhancement of the effect of the nanoscale reinforcement, the tribological properties of the SLM-processed TiC/Ti6Al4V composites are further improved. At an applied load of 15 N, the friction coefficient and wear rate reach 0.303 and 1.221 mm3/m∙N, respectively. • TiC/Ti6Al4V composites with unique nanoscale eutectic TiC reinforcement are prepared by SLM for the first time. • The microstructure formation condition and corresponding evolution mechanism under different parameters are clarified. • The SLM-processed Ti6Al4V/TiC composite shows excellent mechanical and tribological properties. • Mechanical and tribological properties reinforcement mechanism of the SLM-processed Ti6Al4V/TiC composite is established. [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]

Hf-Mo-Si-N films with a series of Si contents were prepared by magnetron sputtering in a mixed Ar/N 2 atmosphere. Microstructure and surface morphologies of films were characterized by XRD, XPS, TEM and AFM. Besides, mechanical and tribological properties were evaluated. With increasing of Si addition, the phase of films transforms from single fcc Hf-Mo-N to nanocomposite structure consisted of Hf-Mo-Si-N crystalline and amorphous Si 3 N 4 phases. The Hf-Mo-Si-N film with 5.4 at.% Si content exhibits improved hardness of 38.6 GPa and enhanced toughness of 3.6 MPa·m1/2, which is ascribed to the synergistic effect of the solid solution strengthen, fine grains and interface strengthening in nanocomposite system. The precipitated amorphous Si 3 N 4 phase could hinder the cracks propagation, which results in higher fracture toughness. The low average friction coefficient of 0.37 and wear rate of 1.8 × 10−6 mm3/N are obtained from the Hf-Mo-Si-N film with 5.4 at.% Si, which is also accompanied with high value of H/E (0.14) and H3/E*2 (0.61 GPa). • Quaternary Hf-Mo-Si-N films were synthesized by DC and RF magnetron co-sputtering. • Hard yet tough nanocomposite films with dispersed a-Si 3 N 4 phases can resist crack propagation. • The proper Si-addition greatly improves tribological properties of films. [ABSTRACT FROM AUTHOR]