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In this study, NbTaMoW medium-entropy alloy films were prepared using a cosputtering apparatus with four sputter guns. Pure-element targets were used for sputtering. The rotational speeds of the substrate holder (RS) were 1–30 rpm. Lower RS values resulted in the formed films exhibiting a multilayer stacked structure with a cyclical gradient concentration. The crystalline phases, mechanical properties, and oxidation behavior of the prepared NbTaMoW films were investigated. The uniformity of the prepared multilayered alloy films increased with the RS value. The monolithic NbTaMoW alloy films prepared at 30 rpm exhibited a single body-centered cubic (BCC) phase, hardness of 12.9 GPa, and Young's modulus of 278 GPa. The BCC phase evolved into a combination of multiple BCC phases when RS was

In this study, TiNbTa and TiNbTaZr films were utilized as protective coatings on a Ti-6Al-4V alloy to inhibit corrosive attacks from NaCl aqueous solution and simulated body fluid. The structural and mechanical properties of multicomponent TiNbTa(Zr) films were investigated. The corrosion resistance of the TiNbTa(Zr)-film-modified Ti-6Al-4V alloy was evaluated using potentiodynamic polarization tests in a NaCl aqueous solution. The results indicate that the TiNbTa(Zr) films with high Ti and Zr contents exhibited inferior corrosive resistance related to the films with high Ta and Nb contents. Moreover, the TiNbTa(Zr)-coated Ti-6Al-4V plates were immersed in Ringer’s solution for eight weeks; this solution was widely used as a simulated body fluid. The formation of surficial oxide layers above the TiNbTa(Zr) films was examined using transmission electron microscopy and X-ray photoelectron spectroscopy, which prevented the elution of Al and V from the Ti-6Al-4V alloy. Ti33Nb19Ta21Zr27, Ti15Nb68Ta8Zr9, and Ti8Nb8Ta79Zr5 films are suggested as preferential candidates for TiNbTa(Zr)/Ti-6Al-4V assemblies applied as biocompatible materials.

This study explored the structural characteristics, mechanical properties, and oxidation behavior of W-enriched TaWSiN films prepared through co-sputtering. The atomic ratios [W/(W + Ta)] of the as-deposited films maintained a range of 0.77–0.81. The TaWSiN films with a Si content of 0–13 at.% were crystalline, whereas the film with 20 at.% Si was amorphous. The hardness and Young’s modulus of crystalline TaWSiN films maintained high levels of 26.5–29.9 GPa and 286–381 GPa, respectively, whereas the hardness and Young’s modulus of the amorphous Ta7W33Si20N40 films exhibited low levels of 18.2 and 229 GPa, respectively. The oxidation behavior of TaWSiN films was investigated after annealing at 600 °C in a 1%O2–Ar atmosphere, and cone-like Ta0.3W0.7O2.85 oxides formed and extruded from the TaWSiN films.

WSiN films were produced through hybrid pulse direct current/radio frequency magnetron co-sputtering and evaluated as diffusion barriers for Cu metallization. The Cu/WSiN/Si assemblies were annealed for 1 h in a vacuum at 500–900 °C. The structural stability and diffusion barrier performance of the WSiN films were explored through X-ray diffraction, Auger electron spectroscopy, and sheet resistance measurement. The results indicated that the Si content of WSiN films increased from 0 to 9 at.% as the power applied to the Si target was increased from 0 to 150 W. The as-deposited W76N24, W68Si0N32, and W63Si4N33 films formed a face-centered cubic W2N phase, whereas the as-deposited W59Si9N32 film was near-amorphous. The lattice constants of crystalline WSiN films decreased after annealing. The sheet resistance of crystalline WSiN films exhibited a sharp increase as they were annealed at 800 °C, accompanied by the formation of a Cu3Si compound. The failure of the near-amorphous W59Si9N32 barrier against Cu diffusion was observed when annealed at 900 °C.

In this study, the feasibility of using ZrO2 coatings, fabricated through the atmospheric pressure plasma jet technique, as top coats in thermal barrier systems was explored. Inconel 617 was used as the substrate material, and sputtered laminated RuAl/RuAlZr/Ru was used as the bond coat. >20-μm-thick ZrO2 coatings were deposited through several iterations of deposition at 500 °C and annealing at 600 °C; here, ZrO2 existed in the tetragonal phase. The tetragonal ZrO2 was stable after annealing at up to 700 °C but transformed into a mixture of tetragonal and monoclinic ZrO2 phases when annealed at >800 °C. The thermal stability of the ZrO2/RuAl/RuAlZr/Ru/Inconel 617 assembly was evaluated at 800–900 °C in air. The variations in volumetric fractions of the tetragonal and monoclinic ZrO2 phases were recorded; 44% of the tetragonal phase remained after 100 h of annealing at 800 °C, whereas 80% of the tetragonal phase had transformed into the monoclinic phase after 4 h of annealing at 900 °C. Observation of BC after annealing at 800 °C indicated that a dense thermally grown oxide scale, comprising O and Al, formed between the ZrO2 and RuAl layers, which impeded the inward diffusion of O. The inhibition of O diffusion declined with the crystallization of the thermally grown oxide scale into the δ-Al2O3 phase when the annealing time was extended.

In this study, TaWN films were fabricated through co-sputtering. The effects of W addition on the structural variation and mechanical properties of these films were investigated. TaWN films formed face-centered cubic (fcc) solid solutions. With the increase in the W content, the fcc phase varied from TaN-dominant to W2N-dominant, which was accompanied by a decrease in the lattice constant and alterations in material characteristics, such as the chemical bonding and mechanical properties. The phase change was further correlated with the bonding characteristics of films examined by X-ray photoelectron spectroscopy. The hardness increased from 21.7 GPa for a Ta54N46 film to 23.2–31.9 GPa for TaWN films, whereas the Young’s modulus increased from 277 GPa for the Ta54N46 film to 302–391 GPa for the TaWN films. The enhancement in films’ mechanical properties was attributed to the strengthening of the solid solution and the phase change. The wear behavior of the fabricated TaWN films was evaluated using the pin-on-disk test. The Ta17W55N28 and Ta36W24N40 films exhibited an abrasive wear behavior and low wear rates of 4.9–7.6 × 10−6 mm3/Nm.

ZrNx (x = 0.67&ndash, 1.38) films were fabricated through direct current magnetron sputtering by a varying nitrogen flow ratio [N2/(Ar + N2)] ranging from 0.4 to 1.0. The structural variation, bonding characteristics, and mechanical properties of the ZrNx films were investigated. The results indicated that the structure of the films prepared using a nitrogen flow ratio of 0.4 exhibited a crystalline cubic ZrN phase. The phase gradually changed to a mixture of crystalline ZrN and orthorhombic Zr3N4 followed by a Zr3N4 dominant phase as the N2 flow ratio increased up to &gt, 0.5 and &gt, 0.85, respectively. The bonding characteristics of the ZrNx films comprising Zr&ndash, N bonds of ZrN and Zr3N4 compounds were examined by X-ray photoelectron spectroscopy and were well correlated with the structural variation. With the formation of orthorhombic Zr3N4, the nanoindentation hardness and Young&rsquo, s modulus levels of the ZrNx (x = 0.92&ndash, 1.38) films exhibited insignificant variations ranging from 18.3 to 19.0 GPa and from 210 to 234 GPa, respectively.

The reactive gas flow ratio and substrate bias voltage are crucial sputtering parameters for fabricating transition metal nitride films. In this study, W&ndash, N films were prepared using sputtering with nitrogen flow ratios (f) of 0.1&ndash, 0.5. W&ndash, N and W&ndash, Si&ndash, N films were then prepared using an f level of 0.4 and substrate bias varying from 0 to &minus, 150 V by using sputtering and co-sputtering, respectively. The variations in phase structures, bonding characteristics, mechanical properties, and wear resistance of the W&ndash, N films were investigated. The W&ndash, N films prepared with nitrogen flow ratios of 0.1&ndash, 0.2, 0.3, and 0.4&ndash, 0.5 displayed crystalline W, amorphous W&ndash, N, and crystalline W2N, respectively. The W&ndash, N films prepared using a nitrogen flow ratio of 0.4 and substrate bias voltages of &minus, 50 and &minus, 100 V exhibited favorable mechanical properties and high wear resistance. The mechanical properties of the amorphous W&ndash, N films were not related to the magnitude of the substrate bias.

Monolithic Hf&ndash, Si&ndash, N coatings and multilayered Hf&ndash, N coatings with cyclical gradient concentration were fabricated using reactive direct current magnetron cosputtering. The structure of the Hf&ndash, N coatings varied from a crystalline HfN phase, to a mixture of HfN and amorphous phases and to an amorphous phase with continuously increasing the Si content. The multilayered Hf48Si3N49 coatings exhibited a mixture of face-centered cubic and near-amorphous phases with a maximal hardness of 22.5 GPa, a Young&rsquo, s modulus of 244 GPa and a residual stress of &minus, 1.5 GPa. The crystalline phase-dominant coatings exhibited a linear relationship between the hardness and compressive residual stress, whereas the amorphous phase-dominant coatings exhibited a low hardness level of 15&ndash, 16 GPa, this hardness is close to that of Si3N4. Various oxides were formed after annealing of the Hf&ndash, N coatings at 600 &deg, C in a 1% O2&ndash, 99% Ar atmosphere. Monoclinic HfO2 formed after Hf54N46 annealing and amorphous oxide formed for the oxidation-resistant Hf32Si19N49 coatings. The oxidation behavior with respect to the Si content was investigated by using transmission electron microscopy and X-ray photoelectron spectroscopy.

Zr&ndash, Si&ndash, N films were fabricated through the co-deposition of high-power impulse magnetron sputtering (HiPIMS) and radio-frequency magnetron sputtering (RFMS). The mechanical properties of the films fabricated using various nitrogen flow rates and radio-frequency powers were investigated. The HiPIMS/RFMS co-sputtered Zr&ndash, N films were under-stoichiometric. These films with Si content of less than 9 at.%, and N content of less than 43 at.% displayed a face-centered cubic structure. The films&rsquo, hardness and Young&rsquo, s modulus exhibited an evident relationship to their compressive residual stresses. The films with 2&ndash, 6 at.% Si exhibited high hardness of 33&ndash, 34 GPa and high Young&rsquo, s moduli of 346&ndash, 373 GPa, which was accompanied with compressive residual stresses from &minus, 4.4 to &minus, 5.0 GPa.

Ta&ndash, Al multilayer coatings were fabricated through cyclical gradient concentration deposition by direct current magnetron co-sputtering. The as-deposited coatings presented a multilayer structure in the growth direction. The oxidation behavior of the Ta&ndash, Al multilayer coatings was explored. The results specified that Ta-rich Ta&ndash, Al multilayer coatings demonstrated a restricted oxidation depth after annealing at 600 &deg, C in 1% O2&ndash, 99% Ar for up to 100 h. This was attributed to the preferential oxidation of Al, the formation of amorphous Al-oxide sublayers, and the maintenance of a multilayer structure. By contrast, Ta2O5 formed after exhausting Al in the oxidation process in an ambient atmosphere at 600 &deg, C which exhibited a crystalline Ta2O5-amorphous Al-oxide multilayer structure.

Zr&ndash, Si&ndash, N films with atomic ratios of N/(Zr + Si) of 0.54&ndash, 0.82 were fabricated through high-power impulse magnetron sputtering (HiPIMS)&ndash, radio-frequency magnetron sputtering (RFMS) cosputtering by applying an average HiPIMS power of 300 W on the Zr target, various RF power levels on the Si target, and negative bias voltage levels of 0&ndash, 150 V connected to the substrate holder. Applying a negative bias voltage on substrates enhanced the ion bombardment effect, which affected the chemical compositions, mechanical properties, and residual stress of the Zr&ndash, N films. The results indicated that Zr&ndash, N films with Si content ranging from 1.4 to 6.3 atom % exhibited a high hardness level of 33.2&ndash, 34.6 GPa accompanied with a compressive stress of 4.3&ndash, 6.4 GPa, an H/E* level of 0.080&ndash, 0.107, an H3/E*2 level of 0.21&ndash, 0.39 GPa, and an elastic recovery of 62&ndash, 72%.

Cr&ndash, Si&ndash, N coatings were prepared through reactive direct current magneton sputtering using a high N2/Ar flow ratio of 1. The addition of Si to improve the mechanical properties and oxidation resistance of Cr&ndash, N coatings was examined. The results indicated that the Cr&ndash, N coatings with an Si content of &lt, 12 at % and an N content of &gt, 50 at % exhibited a cubic CrN phase with a columnar structure, whereas the coatings with 14 at % Si comprised of a nanocomposite structure, and the coatings with 16&ndash, 18 at % Si were near-amorphous. The nanocomposite Cr32Si14N54 coating possessed hardness and Young&rsquo, s modulus values of 17 and 209 GPa, respectively, accompanied with a hardness to effective Young&rsquo, s modulus (H/E*) value of 0.077 and an elastic recovery (We) level of 55%&mdash, all the properties were highest within the as-deposited coating. The addition of Si was also beneficial to reduce the surface roughness and improve the oxidation resistance.

High-Si-content transition metal nitride coatings, which exhibited an X-ray amorphous phase, were proposed as protective coatings on glass molding dies. In a previous study, the Zr–Si–N coatings with Si contents of 24–30 at.% exhibited the hardness of Si3N4, which was higher than those of the middle-Si-content (19 at.%) coatings. In this study, the bonding characteristics of the constituent elements of Zr–Si–N coatings were evaluated through X-ray photoelectron spectroscopy. Results indicated that the Zr 3d5/2 levels were 179.14–180.22 and 180.75–181.61 eV for the Zr–N bonds in ZrN and Zr3N4 compounds, respectively. Moreover, the percentage of Zr–N bond in the Zr3N4 compound increased with increasing Si content in the Zr–Si–N coatings. The Zr–N bond of Zr3N4 dominated when the Si content was >24 at.%. Therefore, high Si content can stabilize the Zr–N compound in the M3N4 bonding structure. Furthermore, the thermal stability and chemical inertness of Zr–Si–N coatings were evaluated by conducting thermal cycle annealing at 270 °C and 600 °C in a 15-ppm O2–N2 atmosphere. The results indicated that a Zr22Si29N49/Ti/WC assembly was suitable as a protective coating against SiO2–B2O3–BaO-based glass for 450 thermal cycles.

In this study, equiatomic Ru–Zr coatings were deposited on Si wafers at 400 °C by using direct current magnetron cosputtering. The plasma focused on the circular track of the substrate holder and the substrate holder rotated at speeds within 1–30 rpm, resulting in cyclical gradient concentration in the growth direction. The nanoindentation hardness levels of the as-deposited Ru–Zr coatings increased as the stacking periods of the cyclical gradient concentration decreased. After the coatings were annealed in a 1% O2–99% Ar atmosphere at 600 °C for 30 min, the internally oxidized coatings shifted their respective structures to a laminated structure, misaligned laminated structure, and nanocomposite, depending on their stacking periods. The effects of the stacking period of the cyclical gradient concentration on the mechanical properties and structural evolution of the annealed Ru–Zr coatings were investigated in this study.

Assumed strain eight-node hexahedral elements with significantly extended range of applicability are presented. These elements are formulated using only standard translational displacements at each of their eight nodes and provide accurate solutions for a variety of benchmark problems such as spacial beams, plates, shells as well as general three-dimensional elasticity problems. The elements with such characteristics are particularly useful to model problems of complex geometry, where different regions of the domain might impose entirely different modeling requirements. The formulation starts with introduction of a parallelepiped domain associated with the given eight-node hexahedral element. Then, the assumed strain field is constructed for that associated parallelepiped domain. It is done by identification of various modes of its deformation and by proper modification of the strain field in the constant and linear bending modes. Strain and displacement extrapolation from the associated parallelepiped to the original hexahedral domain is subsequently used to establish the assumed strain field for the given element. Solutions to some popular benchmark problems demonstrate that the proposed assumed strain hexahedral elements exhibit remarkably high accuracy even when severely distorted and high aspect ratio meshes are used. Another advantage of the present elements is that locking for nearly incompressible materials is also mitigated. Unfortunately, the elements pass the patch test only when their shapes are parallelopipeds.

This study explored the internal oxidation of laminated Hf–Ru coatings by using cyclical gradient chemical concentration distribution along the growth direction. Hf-rich, near-equiatomic, and Ru-rich Hf–Ru coatings were prepared using direct-current magnetron cosputtering. Oxidation was examined by annealing the coatings at 500 and 600 °C in a 1% O2–99% Ar atmosphere for 30 min. The results indicated that internally oxidized laminated Hf–Ru coatings formed after annealing at 600 °C. Hf preferentially oxidized and formed monoclinic HfO2. The Ru-rich Hf0.11Ru0.89 coatings exhibited a higher oxidation resistance and superior mechanical properties.

Ru based laminated coatings with various transition metal solutes were deposited on silicon wafers using a direct current magnetron cosputtering system. After annealing in a 1% O2–Ar atmosphere at 600 °C for 30 min, Ti–Ru, Zr–Ru, Mo–Ru, Hf–Ru, and W–Ru coatings were internally oxidized and maintained a laminated structure, consisting of alternating oxygen-rich and deficient layers stacked along the original growth direction. Conversely, V–Ru and Cr–Ru coatings exhibited external oxidation and failed to maintain the laminated structure after annealing, due to the fast outward diffusion of V and Cr. The variations in crystalline structure and nanohardness of Ru based coatings caused by oxidation after annealing were investigated.