Thermostability,oxidation, and high-temperature tribological properties of nano-multilayered AlCrSiN/VN coatings

In this study, monolithic AlCrSiN, VN, and nano-multilayered AlCrSiN/VN coatings were deposited using a hybrid deposition system combining arc ion plating and pulsed direct current magnetron sputtering. The microstructure, thermostability, mechanical, oxidation and tribological properties of the coatings were comparably investigated. The multilayered AlCrSiN/VN coating exhibited a face-centered cubic (fcc) structure with (200) preferred orientation and showed the highest hardness (30.7 ± 0.5 GPa) among these three coatings due to the multilayer interface enhancement mechanism and higher compressive stress. The AlCrSiN sublayers effectively prevented the V element from rapid outward diffusion to the surface of AlCrSiN/VN coating at elevated temperatures, which improved the oxidation resistance of the coating. Decomposition of V (Cr)–N bonds occurred at annealing temperatures from 800 °C to 1000 °C and V₂N phase appeared at 1100 °C. The AlCrSiN/VN coating showed excellent tribological performance at high temperatures by combining the merits of VN layers for low friction coefficient and AlCrSiN layers for superior oxidation resistance. Compared to VN and AlCrSiN coatings, AlCrSiN/VN coating showed the lowest wear rate of 2.6×10^-15 m³/N·m at 600 °C and lowest friction coefficient of 0.26 at 800 °C with a relativity low wear rate of 39.4×10^-15 m³/N·m.     

Design of cycle structure on microstructure,mechanical properties and tribology behavior of AlCrN/AlCrSiN coatings

AlCrN/AlCrSiN coatings with cycle structure, composed of fcc-CrN, hcp-AlN and amorphous Si₃N₄ phases, were fabricated to protect high speed steel (HSS) tools by high energy ion source enhanced multi-arc ion plating technology with Al₇₀Cr₃₀ and Al₆₀Cr₃₀Si₁₀ alloying targets. With the increasing cycle structure, the crystal grains of AlCrN layers was refined from 60–110 nm to 8–15 nm, and the growth behavior transformed from (200)fcc to the coexistence of both (200)fcc and (111)fcc preferred orientation as demonstrated by GIXRD spectrum, calculated texture coefficient and HRTEM results. The HRTEM results investigated that the inter-planar spacing of CrN(111) was basically equal to that of AlN(0002) with parallel orientation relationship and the interface-1 between the substrate and adhesion layer with a semi-coherent appearance presented a specific orientation relationship. The coating with two cycle structure (Cycle 2) possessed better adhesion strength (HF1 grade, 62.7±1.3 N of Lc2), higher hardness (30.2±1.7 GPa), better fracture toughness (0.099 of H/E, 0.29 GPa of H³/E² and 9.8±0.3 MPa m^1/2 of K_IC under 20 kgf loading), lower friction coefficient (0.54), less wear rate (4.2 × 10^?16 m³/N·m) and longer service life (7.4 m).     

Positive modification on the mechanical,tribological and oxidation properties of AlCrNbSiN coatings by regulating the Nb/Si-doping ratio

The precise control of Nb/Si-doping ratio is the critical factor to tailor AlCrNbSiN coatings with superior comprehensive properties. In this study, the effect of Nb/Si-doping ratio on the microstructure, mechanical, tribological and oxidation properties of AlCrNbSiN coatings was systematically researched. With the increase of Nb/Si-doping ratio, coatings’ microstructures changed from a featureless dense structure to a columnar and equiaxed mixed microstructure gradually. The main phase was transformed from the solid solution phase of h-Al(Cr)N for Nb-free coating (Nb/Si = 0:1) to c-Al(Cr)N solid solution for three Nb-containing coatings (Nb/Si = 1:2, 1:1 and 2:1). When Nb/Si ratio is 1:1, the formation of harmful h-NbN phase was found in the coating. The performance results indicated that, (1) The AlCrNbSiN coating with the Nb/Si ratio of 2:1 achieved optimal hardness (~34.9 GPa), toughness (CPRs ~569.3) and the minimum wear rate of 2.34 × 10⁻⁶ mm³/(N·m); (2) When the Nb/Si-doping ratio is 1:2, the coating exhibited the best oxidation resistance, attributing to the sufficient (Al, Si)O_x oxidation protective layer and only a small amount of AlNbO₄ and CrNbO₄ formed at 1200 °C.     

Effects of Ti2SnC on the mechanical properties and tribological properties of copper/graphite composites

Copper/graphite composites and copper/graphite/Ti₂SnC composites were fabricated through the process of ball-milling, pressing and sintering. The effects of Ti₂SnC as the second lubrication component on the mechanical properties, wear resistance and lubrication properties of copper/graphite composites were studied in this paper. The results showed that copper/graphite/Ti₂SnC composites had better hardness, impact toughness, wear resistance and lubrication performance than copper/graphite composites. The optimum values of hardness, impact toughness, friction coefficient and wear rate of copper/graphite/Ti₂SnC composites were, respectively, 56 HSD, 1.8J/cm², 0.15, 9.126 × 10^?6 mm³/N·m, while these were only 45 HSD, 1.2 J/cm², 0.17, 3.534 × 10^?4 mm³/N·m of copper/graphite composites.     

Influence of hBN content on mechanical and tribological properties of Si3N4/BN ceramic composites

Silicon nitride materials containing 1–5 wt% of hexagonal boron nitride (micro-sized or nano-sized) were prepared by hot-isostatic pressing at 1700 °C for 3 h. Effect of hBN content on microstructure, mechanical and tribological properties has been investigated. As expected, the increase of hBN content resulted in a sharp decrease of hardness, elastic modulus and bending strength of Si₃N₄/BN composites. In addition, the fracture toughness of Si₃N₄/micro BN composites was enhanced comparing to monolithic Si₃N₄ because of toughening mechanisms in the form of crack deflection, crack branching and pullout of large BN platelets. The friction coefficient was not influenced by BN addition to Si₃N₄/BN ceramics. An improvement of wear resistance (one order of magnitude) was observed when the micro hBN powder was added to Si₃N₄ matrix. Mechanical wear (micro-failure) and humidity-driven tribochemical reaction were found as main wear mechanisms in all studied materials.     

Analysis of the mechanical properties of TiN/Ti multilayer coatings using indentation under a broad load range

In this study, physical vapor deposition was used to prepare TiN/Ti multilayer coatings as well as the corresponding monolithic coatings for comparison. Nanoindentation using a large load range (5–4800 mN) and finite element method (FEM) simulations were conducted to investigate the influence of various multilayer structures on the mechanical behavior of multilayer coatings. The nanoindentation results show that the TiN/Ti multilayer coating has the maximum hardness and Young's modulus while retaining good crack resistance and fracture toughness. The FEM results show that increasing the number of layers in the multilayer coatings reduced the hardness and Young's modulus as well as the maximum stress, while it increased the equivalent plastic strain. As the layer thickness ratio increased, both the hardness and Young's modulus gradually increased, and the stress in the coating reached its maximum at the highest thickness ratio. In addition, to consider the effect of the indentation depth on the coating, the influence of the number of layers and the layer thickness ratio on the multilayer coating is combined into the indentation response of the multilayer coating. Therefore, we establish an expression describing the relationship between the number of layers and the ratio of the layer thickness to the mechanical properties of TiN/Ti multilayer coatings.     

Microstructure and mechanical properties of Si3N4f/Si3N4 composites with different coatings

The Si₃N₄ coating and Si₃N₄ coating with Si₃N₄ whiskers as reinforcement (Si₃N_4w-Si₃N₄) were prepared by chemical vapor deposition (CVD) on two-dimensional silicon nitride fiber reinforced silicon nitride ceramic matrix composites (2D Si₃N_4f/Si₃N₄ composites). The effects of process parameters of as-prepared coating including the preparation temperature and volume fraction of Si₃N_4w on the microstructure and mechanical properties of the composites were investigated. Compared with Si₃N₄ coating, Si₃N_4w-Si₃N₄ coating shows more significant effect on the strength and toughness of the composites, and both strengthening and toughening mechanism were analyzed.     

Microstructural,mechanical and tribological properties of nanostructured YSZ coatings produced with different APS process parameters

Plasma sprayed ceramic coatings can be used in turbine engines as thermal barrier or abradable coatings, in order to improve the durability of the components as well as the efficiency. The presence of nanostructures, deriving from partial melting of agglomerated nanostructured particles, represents an interesting technological solution in order to improve their functional characteristics. In this work nanostructured yttria stabilized zirconia (YSZ) coatings were deposited by air plasma spraying (APS). The influence of the main process parameters on their microstructural, mechanical and tribological properties was investigated by scanning electron microscopy (SEM), indentation techniques at micro- and nano-scale and wear tests, respectively. Their porous microstructure was composed of well melted overlapped splats and partially melted nanostructured areas. This bimodal microstructure led to a bimodal distribution of the mechanical properties. An increase of plasma power and spraying distance was able to produce denser coatings, with lower content of embedded nanostructures, which exhibited higher elastic modulus and hardness as well as lower wear rate.     

Microstructure and optical properties of Ag/ITO/Ag multilayer films

Transflective and highly conductive Ag/ITO/Ag multilayer films were prepared by magnetron sputtering on glass substrates. The microstructure and optical properties of Ag/ITO/Ag multilayer films were systematically investigated by X-ray diffraction, scanning electron microscopy, and ultraviolet-visible spectroscopy. The optical properties of the multilayer films were significantly influenced by the thickness of the Ag surface layer from 3.0 to 12.6 nm. The multilayer film of Ag9.3nm/ITO142nm/Ag9.3nm shows the best comprehensive property. It could satisfy the requirement for transflective LCD.     

Tribomechanical and microstructural properties of cathodic arc-deposited ternary nitride coatings

Sintered carbides are promising materials for surfaces that are exposed to extreme wear. Owing to their high service load, ceramic-based thin films are coated on carbides using different techniques. In this study, non-toxic and cobalt-free powder metallurgy-sintered carbide samples were coated with TiN, TiAlN, CrAlN, and TiSiN ceramic-based thin film coatings by cathodic arc physical vapor deposition. The microstructure (phase formation, coating thickness, surface roughness, and topography), mechanical properties (hardness, modulus of elasticity, and plasticity indices), and tribological properties (nanoscratch and wear behavior) of the thin film coatings were investigated. No cracks or defects were detected in these layers. The ceramic-based ternary nitride thin film coatings exhibited better mechanical performance than the TiN coating. The TiN thin film coating had the highest average surface roughness, which deteriorated its tribological performance. The ternary nitride thin film coatings exhibited high toughness, while the TiN thin film coating exhibited brittle behavior under applied loads when subjected to nanoscratch tests. The wear resistance of the ternary nitride coatings increased by nearly 9–17 times as compared to that of the TiN coating and substrate. Among all the samples investigated, the substrate showed the highest coefficient of friction (COF), while the TiSiN coating exhibited the lowest COF. The TiSiN thin film coating showed improved mechanical and tribological properties as compared to other binary and ternary nitride thin film coatings.     

Effect of Ti particle size on mechanical and tribological properties of TiCN coatings prepared by reactive plasma spraying

Titanium carbonitride (TiCN) coatings were successfully fabricated by reactive plasma spraying (RPS) from agglomerated Ti-graphite feedstock. The effect of Ti particle size on the microstructure and phase composition of plasma sprayed TiCN coatings was investigated. The Vickers microhardness of coatings was measured by a Microhardness Test and the corresponding Weibull distribution were also analyzed. In addition, a pin-on-disk tribometer was employed to determine the trobological properties of coatings. Results show that all the coatings consist of TiC_xN_1−x (0 ≤ x ≤1) and minor Ti₂O phases, and the amount of Ti₂O increases with the increase of Ti particle size. The Weibull distribution of Vickers microhardness of all the coatings shows apparent scattering, while the coating sprayed with Ti particle size of 28 µm exhibits a relatively even distribution. Compared with the coating sprayed with Ti particle size of 14 µm or 48 µm, the coating sprayed with Ti particle size of 28 µm exhibits improved mechanical and tribological properties, which are attributed to the high microhardness and strong bonding strength.     

Optimization of mechanical and tribological properties of carbon fabric/resin composites via controlling ZnO nanorods morphology

The multi-scale reinforcements of ZnO nanorods/carbon fabric with different morphologies were obtained using a simple water bath method via controlling the concentration of growth solution for a new application in wet friction materials. The ZnO nanorods/carbon fabric were characterized via X-ray diffraction, Scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectra. As a result, the ZnO nanorods/carbon fabric/resin composite (sample CP3) possesses the maximum bending and tensile strength of 62.7?MPa and 170.0?MPa, which increases by 40.2% and 59.1% compared with that of bare carbon fabric/resin composite due to the best mechanical interlocking and chemical adhesion at the interfacial region of the composite. Meanwhile, the wear rate of the sample CP3 decreases obviously by 81.5% together with stable friction coefficient under various friction condition. From view point of material design, it is necessary to control the morphologies of ZnO nanorods to optimize mechanical and tribological properties of ZnO nanorods/carbon fabric/resin composites.     

Growth,mechanical properties,and tribological performance of TiAlN/NbN and NbN/TiAlN bilayer coatings

Three different coatings, namely TiAlN, TiAlN (external)/NbN (internal) and NbN (external)/TiAlN (internal), were deposited on cemented carbides by arc ion plating. The comparative investigation conducted in this study elucidates the effect of the NbN layer and coating systems on the growth, mechanical properties, and tribological performance of the coatings. The results showed that the surface of the TiAlN and TiAlN/NbN coatings was smoother when TiAlN served as the external layer. The NbN/TiAlN coating, wherein NbN formed the external layer, had a much rougher but more symmetrical surface. With the introduction of the NbN layer, the increased micro stress induced a lower adhesion strength in the TiAlN/NbN and NbN/TiAlN coatings. The TiAlN/NbN and NbN/TiAlN coatings exhibited higher hardness and hardness/effective elastic modulus (H/E*). During the friction test, when the temperature was elevated to 700 °C, the tribological performance of the monolayer TiAlN coating was the lowest because of the TiO₂-induced breakage of the dense tribo-oxide film. The NbN layer participated in the formation of a NbO_x film at elevated temperatures, which was responsible for the high tribological performance of the two bilayer coatings. When the NbN layer was on the outermost layer and in direct contact with the elevated temperature atmosphere, the NbN/TiAlN coating generated a tribo-oxide film with high integrity, and its coefficient of friction decreased by 27% of that at room temperature. Therefore, the NbN/TiAlN coating exhibited the highest wear resistance at 700 °C.     

TaB2-based ceramics: Microstructure, mechanical properties and oxidation resistance

TaB₂-based ceramics were hot pressed in low vacuum with addition of 5-10 vol% MoSi₂. Temperatures in the range of 1680-1780 °C led to relative density around 90-95%. The hardness was about 18 GPa, the fracture toughness 4.6 MPa m^1/2 and the room temperature flexural strength was around 630 MPa, but abruptly decreased above 1200 °C to 220 MPa. The composite containing 10 vol% of MoSi₂ was tested in a bottom-up furnace in the temperature range 1200-1700 °C for 30 min. The microstructure appeared covered by a SiO₂ layer, whose thickness increased with the temperature, but the bulk remained unaltered up to 1600 °C. At 1700 °C the specimen vaporized. Nanoindentation was employed on the oxidized cross sections in order to detect eventual mechanical properties modification associated to chemical/microstructural change, like formation of Ta-B-O solid solutions.     

Mechanical properties and tribological performance of alumina matrix composites reinforced with graphene-family materials

This paper introduce the formation of alumina matrix composites reinforced with multilayered graphene, graphene oxide and nickel-phosphorus coated multilayered graphene. The powder metallurgy technique followed by the Spark Plasma Sintering (SPS) method were utilized to fabricate the specimens. The influence of graphene-family material additions on microstructure was investigated, and correlated with measurements of mechanical properties. The emphasis of the research has been placed on the tribological performance conducted with the use of the ball-on-disc method under loads of 10 N and 30 N. Both the wear tracks of composites and the corresponding counterparts were carefully analysed, to evaluate the combined influence of mechanical properties and tribofilm formation on the measured wear rates. All results were compared to pure alumina as a reference specimen.     

Microstructure and mechanical properties of carbon/carbon composites with PyC/SiC/TiC multilayer interphases

Carbon/carbon composites with PyC/SiC/TiC multilayer interphases (CCs-PST) have been successfully prepared by a joint process of chemical vapor deposition and carbothermal reduction. Effect of the Ti(OC₄H₉)₄/C₆H₄(OH)₂ molar ratio on the morphology of TiC particles was investigated and the ratio was optimized as 8:1. When the Ti(OC₄H₉)₄/C₆H₄(OH)₂ molar ratio was 8:1, many homogeneously distributed TiC nanoparticles with the sizes of 100–500 nm on the fibers were observed. The structural evolution of CCs-PST was discussed and the mechanical properties of as-prepared materials were investigated by flexural and interlaminar shear tests. The resulted composites demonstrated a PyC and SiC mixed inner interphase with the thickness of 0.5–1 $\mathrm{\mu }\mathrm{m}$ and a TiC outer interphase with a thickness about 0.5 µm. Flexural strength of 201.45 ± 5.27 MPa and modulus of 21.21 ± 1.58 GPa showed a 41.7% and 7.83% improvement respectively as compared with that of the neat CCs. The interlaminar shear strength of CCs-PST was 66.71 ± 4.87 MPa, which was 51.20% higher than that of the CCs. The improved mechanical properties were attributed to the enhanced interface bond between fibers and matrix induced by the PST.     

Microstructure,mechanical and tribological properties of TaCN composite films by reactive magnetron sputtering

In this paper, a series of TaCN composite films with different carbon content were deposited by the magnetron sputtering system and the microstructure, mechanical and tribological properties were investigated. The results showed that the deposited TaCN films exhibited a three-phase of face-centered cubic (fcc) Ta(C,N), hexagonal closed-packed (hcp) Ta(C,N) and amorphous CNx. With the increase of carbon content, the hardness of the TaCN films first increased and then decreased, after reaching a maximum of 33.1 GPa; the adhesion strength increased gradually; the coefficient of friction decreased monotonically and the wear property initially improved and then weakened at room temperature. The coefficient of friction of the TaCN film at 28.21 at.% carbon decreased first, then increased and then decreased again and its high-temperature wear rate first decreased slightly and then increased, as the temperature increased from room temperature (RT) to 600 °C. The TaCN film at 28.21 at.% carbon exhibited excellent an elevated-temperature tribological properties.     

Effect of substrate rotational speed during deposition on the microstructure,mechanical and tribological properties of a-C:Ta coatings

Rotational speed has an important influence on the performance of coating materials. The a-C:Ta composite coatings were prepared by controlling the substrate rotational speed during deposition process using PVD technique. The results showed that the coating transformed from dense structure to columnar structure. Due to the changes of deposition time and the vapor incident angle of the sputtering ions, the sp² hybrid structure increased and the C–Ta bonds contents decreased as a function of the rotational speed, which led to the improvement of adhesion force. The average friction coefficient of the composite coatings did not fluctuate significantly for the amorphous carbon matrix and the transfer films formed during friction, while the wear rates were gradually increased. The sample at 0.5 rpm possessed the lowest wear rate, which was mainly associated with the cooperative behavior of the dense structure and the formation of TaC nanoclusters in the composite coating.     

Microstructure and mechanical properties of nanomultilayered AlTiN/Cu coatings prepared by a hybrid system of AIP and PDCMS

Due to its excellent lubricity and immiscibility with nitride phase, Cu has been added to nitrides to form a typical nanomultilayer structure. In this work, a hybrid deposition of AIP and PDCMS was applied to synthesize the multilayered AlTiN/Cu coatings, and the relationship between microstructure and mechanical properties was explored. The Cu-free AlTiN coating exhibited a c-TiAlN phase with a strong (200) preferred orientation. After adding Cu layer, the microstructure changed from a dense columnar structure into a featureless structure and then a fine-grained structure. As the Cu layer thickness reached 5.1 nm, the AlTiN/Cu(18.4 at.%) coating showed a double-phase of c-TiAlN and c-Cu. The thickness modulation period of Cu/AlTiN sublayer exhibited an excellent linear relationship with the content ratio of Cu/(Al + Ti). After adding Cu, the ion bombardment effect was weakened, the AlTiN/Cu(2.9 at.%) coating exhibited the lowest surface roughness of 18.9 nm, and the hardness gradually decreased from 34.6 to 13.2 GPa, accompanied by a relaxation of residual stress. Due to a high H/E* ratio, a maximum adhesion strength of 83.0 N was obtained at 2.9 at.% Cu.     

Effect of hBN addition on the fabrication,mechanical and tribological properties of Sialon materials

This work aims to investigate the effect of hBN on the friction and wear resistance of Sialon composite. Sialon and its composite with 10 wt% hBN were fabricated by SPS sintering. The effect of hBN additive on the phase composition, microstructure, densification behavior, mechanical and dry sliding tribological properties of Sialon material was studied. Being sintered at 1600 °C for 10 min, compared to monolithic Sialon, Sialon-hBN composite has more refined β-Sialon grains with smaller aspect ratios and slightly declined relative density. The hardness of the Sialon-hBN composite was reduced due to the weak bonding between Sialon and hBN grains. Nevertheless, its fracture toughness increased ascribing to the toughening mechanisms, including crack deflection and crack bridging. hBN had an essential impact on the tribological performances of the composite due to its lower friction coefficient and good lubrication action. Under the same densification level (i.e., with a relative density of around 97.5%), the friction and wear resistance of Sialon-hBN composite were much better than monolithic Sialon. The main wear mechanisms were tribolayer formation, oxidized wear, and abrasive wear.