Effect Of Modulation Period Research Articles

Effect of modulation period on the mechanical and tribological behavior of (CrNbTiAlV)CN/MoN coatings

Effect of modulation period on the mechanical and tribological behavior of (CrNbTiAlV)CN/MoN coatings

Effect of Modulation Period on the Thermally-Induced Solid-State Reactions in Ni/Ti Thin Films

Effect of Modulation Period on the Thermally-Induced Solid-State Reactions in Ni/Ti Thin Films

High hardness and toughness potential TiN/TiSiN gradient nano-multilayer coating structure by finite element study

The low toughness and high brittleness of hard coatings are common defects that seriously affect their application in various fields. In order to ensure high hardness while increasing the toughness of the coatings, an evaluation model for the mechanical properties of TiN/TiSiN coatings has been established and validated by the finite element method. The effects of modulation period and modulation ratio on the hardness and toughness of TiN/TiSiN nano-multilayer coatings are investigated. Subsequently, a modulation ratio gradient structure is introduced to optimize the coating structure and thus achieve the toughening effect. The results indicate that the load on the low modulation ratio coating is distributed over a larger surface area and can resist greater loads, and that this structure has higher hardness and deformation resistance. However, the low modulation ratio structure produces a higher shear stress concentration region inside the structure. The modulation ratio gradient structure can take into account the advantages of low and high modulation ratios, it can ensure the high hardness of 34 GPa while dramatically reducing the maximum principal stress by about 46 %, and the maximum shear stress by 14 %, which effectively inhibiting crack formation and enhancing the toughness of the nano-multilayer coatings.

Effect of modulation period and thickness ratio on the growth and mechanical properties of heteroepitaxial c-Ti0.4Al0.6N/h-Cr2N multilayer films

c-TiAlN/h-Cr2N multilayer thin films, with modulation period λ of 10 nm, 20 nm, and 30 nm and different Cr2N/ λ thickness ratios (25 %, 50 % and 75 %), were deposited on c-plane sapphire using reactive DC magnetron sputtering. All multilayers exhibited preferred orientation [Cr2N(0001)/ TiAlN(111)]x, regardless of the modulation period and thickness ratios. X-ray diffraction φ-scans revealed an influence of the Cr2N layer thickness on the overall orientation quality of the multilayer, where the thicker the Cr2N layer the higher orientation quality. Atomically resolved high-angle annular dark-field scanning transmission electron microscopy revealed well defined and homogeneous atom stacking in the Cr2N layers. In contrast, the cubic TiAlN layer was found to be composed of coherent cubic AlN-rich and TiN-rich regions. Additionally, the TiAlN layers were found with a higher density of grain boundaries compared to the Cr2N layers. Mechanical properties evaluation revealed that the film with a 20 nm period and 75 % Cr2N thickness ratio exhibited the highest hardness of 27.11 ± 0.72 GPa and an reduced elastic modulus of 349.1 ± 6.84 GPa. The hardness increased as the thickness of Cr2N increased, until reaching 10 nm, after which it remained at a high level (∼ 25 GPa).

Effects of gradient structure and modulation period of Ta/TaN/Ta(C,N)/Ta-DLC multilayer coatings prepared by HiPIMS

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.

Effect of modulation period on microstructure and mechanical properties of (AlSiTiVNbCr)N/(AlSiTiVNbCr)CN nano-multilayer films

(AlSiTiVNbCr)N/(AlSiTiVNbCr)CN nano-multilayer films were prepared by reactive magnetron sputtering under different modulation periods. The effects of modulation period on the microstructural evolution and mechanical properties of the films were studied. The microstructure and mechanical properties of the films were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), nano-indentation instrument and scratch test. The results show that the modulation periods of (AlSiTiVNbCr)N/(AlSiTiVNbCr)CN nano-multilayer films are 133.00 nm, 57.80 nm, 23.12 nm and 7.71 nm, respectively. All films exhibit a single face-centered-cubic (FCC) structure. With the decrease of modulation period, the intensity of (220) diffraction peak increases significantly, and the intensity of (200) diffraction peak disappear, indicating that the preferred orientation of the films is (220). When the modulation period is 7.71 nm, the film exhibit an outstanding hardness of 47.64 ± 5 GPa, elastic modulus of 318.36 ± 26 GPa, and adhesion strength of 78 N with the highest H/E and H2/E. The strengthening effect is mainly attributed to the super-hard effect, which caused by the decrease of grain size and the increase of interfaces. Based on the outstanding properties of nano-multilayer films, (AlSiTiVNbCr)N/(AlSiTiVNbCr)CN films present a potential application prospect on cutting tools.

Effect of modulation period on structure and mechanical properties of WB2/a-WBC films deposited by direct-current magnetron sputtering

WB2/a-WBC multilayer films with different modulation periods ranging from 145 to 830 nm were synthesized by direct-current magnetron sputtering. The effect of modulation period (Λ) on structure and tribo-mechanical properties of the WB2/a-WBC multilayer films was studied. The WB2 monolayer grows preferentially along (101) plane. However, the multilayered structure changes the growth of WB2 sublayers to (001) plane, and a transition layer with composition gradient distribution is formed at the interface between the two sublayers. Consequently, WB2, WB2(C) solid solution and a-WC are detected in the WB2 sublayer, while a-WBC, a-WC and a-C are found in the WBC sublayer. As the modulation period decreases, the residual compressive stress (-384∼-827 MPa) of the WB2/a-WBC films increases first and then decreases, and the hardness of the WB2/a-WBC films (18.8∼23.7 GPa) gradually increases under the joint action of solid solution strengthening and interface strengthening. Moreover, the fracture toughness of the WB2/a-WBC films is also improved greatly resulting from the multilayered structure with the soft a-WBC sublayers. The wear mechanism of the WB2/a-WBC films is a mixture of abrasion and lubrication, and the friction coefficient and wear rate of the WB2/a-WBC films are lower than those of the WB2 and WBC monolayer films because of their excellent toughness and lubricating effect as well as moderate hardness. Comprehensively, the WB2/a-WBC films with Ʌ=830 and 415 nm display lower friction coefficient (∼0.08) and wear rate (1.14∼1.24 × 10−7 mm3/mN).

Tribological properties, oxidation resistance and turning performance of AlTiN/AlCrSiN multilayer coatings by arc ion plating

In this study, AlTiN and AlTiN/AlCrSiN coatings have been synthesized using arc ion plating for high-speed yet dry cutting applications. The effects of modulation period (from 17.8 to 4.2 nm) on microstructure, mechanical properties as well as high-temperature tribological and oxidation behavior of AlTiN/AlCrSiN multilayer coatings were investigated. AlTiN/AlCrSiN multilayer coatings exhibit a single-phase face-centered cubic structure with fine columnar grain morphologies. With the optimal modulation period of 8.3 nm, the multilayer coating can possess the highest hardness, the ratio of hardness to effective modulus and adhesion strength, thus exhibits the best wear resistance at elevated temperatures. Besides, the introduction of AlCrSiN sublayers significantly improves the oxidation resistance of AlTiN, which was oxidized entirely after heating up to 1000 °C in the air. Whereas, AlTiN/AlCrSiN multilayer coatings remain most of the nitride structure uninfluenced with a dense oxide scale (~0.3 μm thick) above. Comparing with AlTiN, the AlTiN/AlCrSiN (Λ = 8.3 nm) coated cemented carbide insert shows a notably longer lifetime during the process of high-speed yet dry machining SKD11, where the primary failure mode is the flank wear resulting from abrasive, adhesive and oxide wear.

Characterization and mechanical properties of TiN/TiAlN multilayer coatings with different modulation periods

The TiN/TiAlN nanomultilayer coatings with different modulation periods were deposited successfully on M2 high-speed steel by a pulsed bias arc ion plating system. The effect of modulation period on the microstructure and mechanical properties was investigated. With the increasing of deposition period, the Al contents in TiN/TiAlN multilayer coatings monotonically increased continuously a little from 0.135 to 0.142, whereas the Ti and N contents were nearly constant. The microstructure TiN/TiAlN multilayer coatings were crystallized with preferred orientation in (111) crystallographic planes. At modulation period of 164 nm, the nanohardness reached a maximum of 38.9 GPa. The Young’s modulus values were in the range of 418–591 GPa. The adhesion strength reached a maximum of 66.2 N at modulation period of 54 nm.

The effect of modulation period on the mechanical and wear properties of TiAgN/W2N coatings

TiAgN/W2N nanoscale multilayered coatings with various modulation periods from 1.0 to 9.0nm were prepared by alternating deposition of TiAgN and W2N. The microstructure, hardness and wear performances were analyzed by XRD, HRTEM, nano-indentation CSM, SEM, Raman and Bruker profilometer. The maximum hardness, 27.6GPa, was obtained for the TiAgN/W2N nanoscale multilayered coating with modulation period of 2.0nm, which is an increase of 72.5% over the rule of mixture hardness value (16.0GPa) of TiAgN and W2N coatings. The wear resistance of TiAgN coating was improved greatly by nanoscale multilayered structurization with W2N due to the higher hardness. With increasing the tested temperature, the increase of the wear rate of TAW coatings is attributed to the increase of these oxides.

Microstructure evolution in multilayer c-TiAlN/TiN coatings during spinodal decomposition — A phase-field study

By means of the combined model, i.e., the phase-field model with finite interface dissipation in combination with the modified Cahn–Hilliard model, together with the materials parameters comprehensively verified in monolithic c-TiAlN coatings, the microstructure evolution in multilayer c-Ti[Formula: see text]Al[Formula: see text]N/TiN coatings annealed at [Formula: see text]C was quantitatively simulated by directly comparing with the experimental data. The sharp interface between c-TiN and c-Ti[Formula: see text]Al[Formula: see text]N layers in the as-deposited state was found to change into a diffuse one, which can act as highly effective obstacles against dislocation motion. Moreover, the simulations indicate that the spinodal decomposition occurs in the Ti[Formula: see text]Al[Formula: see text]N layer and the decomposed layer becomes thinner, which is in good agreement with the experimental observation. In addition, the effect of modulation period and modulation ratio on microstructure evolution in c-Ti[Formula: see text]Al[Formula: see text]N/TiN coating was further studied. The relatively smaller modulation period can generate more layers in the real scale of coatings, which can help to strengthen the coatings due to refinement of grains and restriction of dislocations. As for the modulation ratio, when the value decreases from 5:1 to 1:1, Ti atoms in the decomposed layer disappear faster. A further extension into a larger-sized simulation was also performed.

Effects of modulation period on microstructure, mechanical properties of TiBN/TiN nanomultilayered films deposited by multi arc ion plating

TiBN/TiN multilayered coating with different modulation periods (bilayer thickness) have been synthesized using typical cathodic arc plasma deposition equipment. The objective of this work is to study the influence of modulation period on the microstructure, mechanical and tribological properties. TiBN/TiN multilayer coatings exhibited a TiN (111), (200), (220) and TiB2 (220) crystallographic orientations and preferred TiN (111) orientation. With the decrease of modulation period from 12 nm to 1.9 nm, the mole ratio of B increased from 0.079 to 0.162 in addition to the average mole ratio of N was about 0.39 steadily, while the mole ratio of Ti decreased from 0.506 to 0.407. The microstructure of TiBN/TiN multilayered coating evolves form nanocrystalline TiN/a-BN to nanocomposite Ti(B,N) with an dense amorphous BN phase, The maximum values of hardness and elastic modulus reached 31.6 GPa and 336 GPa with a bilayer period of 1.9 nm and B:Ti ratio of 2:5.

Microstructure and superhardness effect of VC/TiC superlattice films

Vanadium carbide/titanium carbide (VC/TiC) superlattice films were synthesized by magnetron sputtering method. The effects of modulation period on the microstructure evolution and mechanical properties were investigated by EDXA, XRD, HRTEM and nano-indentation. The results reveal that the VC/TiC superlattice films form an epitaxial structure when their modulation period is less than a critical value, accompanied with a remarkable increase in hardness. Further increasing the modulation period, the hardness of superlattices decreases slowly to the rule-of-mixture value due to the destruction of epitaxial structures. The XRD results reveal that three-directional strains are generated in superlattices when the epitaxial structure is formed, which may change the modulus of constituent layers. This may explain the remarkable hardness enhancement of VC/TiC superlattices.

On the Frequency-Independent Modes of a Four-Arm Modulated Arm Width Spiral

This paper shows that among frequency independent (FI) conformal antennas, the modulated arm width (MAW) spiral has the simplest architecture for measuring both polarization and angle-of-arrival (AOA) instantaneously if frequency is known. The theory, design and performance of equiangular four-arm MAW spiral antennas when utilizing both sum modes (± 1) and difference mode ( +2) for direction-finding applications are discussed. It is shown that simultaneous dual-polarization and multi-mode capability is not achievable in more commonly-used four-arm spiral and sinuous antennas. While the co-polarized modes 1, 2 and 3 are well-researched with single-polarized four-arm equiangular spirals, they have not been utilized or controlled on a four-arm MAW spiral. Effects of modulation period on cross-polarization, pattern symmetry, gain, and impedance for all three pattern modes are investigated. The studies are carried out using full-wave modeling and a prototype MAW geometry is built and evaluated with a beamformer to demonstrate its wideband, dual-polarized, multi-mode capability.

Modulated internal electric field, dielectric susceptibility and polarization in ferroelectric superlattices

A thermodynamic model for describing interface intermixing in a superlattice combining a ferroelectric and a paraelectric is developed. Formation of intermixed layer at interfaces leads to a periodic modulation of ferroelectric properties in these superlattices. Spatially-varying internal electric field, dielectric susceptibility and polarization of these superlattices are calculated. Effects of modulation period and temperature on the internal electric field, dielectric susceptibility and polarization of these superlattices with inhomogeneous properties are examined. Correlation between these ferroelectric properties is established and discussed.

Effect of Modulation Period on the Structure and Mechanical Properties of Nanoscale W/ZrB2 Multilayered Coatings

Nanoscale W/ZrB2 multilayered coatings were prepared by rf magnetron sputtering system at room temperature. SEM, XRD, surface profiler and nano-indenter were employed to investigate the influences of modulation period (Λ) on the microstructure and mechanical properties of the films. The results showed that nanoscaled coatings had clear multilayered structure and almost all of multilayered coatings possess higher hardness and elastic modulus than the rule-of-mixtures value of monolithic W and ZrB2 coatings. At Λ=30nm, W/ZrB2 multilayered with mixed polycrystalline texture exhibited the highest hardness of 41.5GPa with lower residual stress.

Effect of Modulation Period and N + Beam Bombarding Energy on the growth of Nanoscale ZrB2/AlN Multilayered Coatings Prepared by IBAD

Monolithic ZrB2, AlN, and ZrB2/AlN multilayered coatings have been synthesized by ion beam assisted deposition at room temperature. Scanning electron microscopy, X-ray diffraction, XP-2 profiler and nano indenter were employed to investigate the influences of modulation period and N+bombarding energy on microstructure and mechanical properties of the coatings. Most of multilayered coatings revealed higher hardness and elastic modulus than the rule-of-mixtures value of monolithic ZrB2 and AlN coatings. N+bombardment at 300eV resulted in ZrB2/AlN multilayered coating the highest hardness (31.2GPa) and elastic modulus (372.2GPa). This hardest multilayer also showed the improved residual stress and fracture resistance. These improved performances are likely a result of more efficient momentum transfer to the deposition particles due to the proper N+bombarding energy.

Ti/TiN multilayer thin films deposited by pulse biased arc ion plating

In this work, the effect of modulation period (Λ) on Ti/TiN multilayer films deposited on high-speed-steel (HSS) substrates using pulse biased arc ion plating is reported. The crystallography structures and cross-sectional morphology of Ti/TiN multilayer films were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM), respectively. Their mechanical properties were determined via nanoindentation measurements, while the film/substrate adhesion via the scratch test. It was found that the highest hardness value reached 43GPa for the modulation period of 54nm, while the film/substrate adhesion also reached the highest value of 83N. Furthermore, the hardness enhancement mechanism in the multilayer films is discussed.

The effects of modulation period, modulation ratio, and deposition temperature on microstructure and mechanical properties of ZrB2/W multilayers

Monolithic ZrB2, W coatings and ZrB2/W multilayers with different modulation periods and modulation ratios were synthesized by ion beam assisted deposition at room temperature and 400°C. X-ray diffraction (XRD), scanning electron microscopy (SEM), surface profiler, and nanoindention were employed to investigate the influences of the deposition temperature and the modulation period on the growth, textures, interface structure, and mechanical properties of the multilayers. The results indicated that the multilayer with modulation period of 13 nm synthesized at room temperature possessed a higher hardness of 23.8 GPa. Deposition temperature gave a significant contribution to mechanical property enhancement. The 400°C-deposition temperature led to a maximum hardness and elastic modulus value of 32.1 and 399.1 GPa for ZrB2/W multilayer with a modulation period of 6.7 nm. Its critical load increased to 42.8 mN and residual stress decreased to −0.7 GPa. A higher deposition temperature can cause an increase in interfacial atomic mixture and mobility of surface species, which induceds an increase in areal atomic density and dislocation pinning. These results as well as small nanoscale grain sizes should be related to hardness increase.

Phase transformation of AlN in AlN/VN nanomultilayers and its effect on the mech anical properties of films

AlN/VN nanomultilayers were prepared by reactive magnetron sputtering method. Th e effect of modulation period on the microstructure and mechanical properties of AlN/VN nanomultilayers were studied in this work. The results show that AlN exi sts in metastable cubic structure (c-AlN) at small modulation period and forms c oherent epitaxial grown superlattice with VN. At larger modulation periods, AlN transforms from cubic structure to stable hexagonal structure (h-AlN),and the na nomultilayers form a “brick-wall” structure with nanometer grains. The discuss ion shows that the template effect of VN is beneficial to the growth of c-AlN, b ut cannot increase its critical thickness remarkably.