Search Results (134)

In this study, a Ag/ZrO₂ hybrid coating prepared by the sol–gel method on a β-type Ti45Nb alloy was applied by the spin coating technique, and the microstructural, mechanical, electrochemical, and tribological properties of the surface were evaluated in a multi-dimensional manner. The hybrid solution was prepared using zirconium propoxide and silver nitrate and stabilized through a low-temperature two-stage annealing protocol. The crystal structure of the coating was determined by XRD, and the presence of dense tetragonal ZrO₂ phase and crystalline Ag phases was confirmed. SEM-EDS analyses revealed a compact coating structure of approximately 1.8 µm thickness with homogeneously distributed Ag nanoparticles on the surface. As a result of the electrochemical corrosion tests, it was determined that the open circuit potential shifted to more noble values, the corrosion current density decreased, and the corrosion rate decreased by more than 70% on the surfaces where the Ag/ZrO₂ coating was applied. In the tribological tests, a decrease in the coefficient of friction, narrowing of wear marks, and significant reduction in surface damage were observed in dry and physiological (HBSS) environments. The findings revealed that the Ag/ZrO₂ hybrid coating significantly improved the surface performance of the Ti45Nb alloy both mechanically and electrochemically and offers high potential for biomedical implant applications. Full article

Due to their excellent mechanical properties and good biocompatibility, titanium (Ti) and its alloys are widely used as biomaterials. However, when implanted in the body, metallic materials may cause serious complications such as wear and infection, leading to patient discomfort and, in some cases, the need for revision surgery. Micro-arc oxidation (MAO) is a surface modification technique that offers a promising strategy to overcome these challenges. This study investigated the impact of the microstructure of Ti-25 Ta-xNb alloys (x = 10, 20, and 30 wt%) and the variation in applied voltage during the MAO process on the characteristics of the TiO₂ oxide coatings formed. The alloys were treated by MAO at 200, 250, and 300 V using a bioactive electrolyte containing Ca, P, Mg, and Ag. EDS, SEM, XRD, Raman spectroscopy, and adhesion tests performed characterization. Results indicated that Nb addition stabilized the β phase and anticipated the potentiostatic regime. Increasing the voltage supplied to the system provides greater energy, prolonging the galvanostatic regime and promoting the formation of larger and more uniform pores. The oxide coating thickness ranged from approximately 3 to 10 μm, with a tendency to decrease at higher voltages. The coatings exhibited low c, with anatase and rutile phases predominating, the applied voltage and Nb concentration influencing their relative proportions. Even in small amounts, all electrolyte elements (P, Mg, and Ag) were successfully incorporated into the coatings under all conditions. Raman and XRD analyses confirmed a decrease in anatase and an increase in rutile phases with increasing voltage and Nb content. Mechanical testing revealed good adhesion of the coatings in all samples, with the best results obtained at 200 V. The findings demonstrate that the developed coatings exhibit promising characteristics for future surface engineering strategies aimed at improving the performance of metallic biomaterials. Full article

The creation of coatings by the cathodic arc evaporation method has outstanding advantages: these coatings are highly durable and wear-resistant, especially since the method has an intense ionization process and the atoms can penetrate deep into the surface substrates, resulting in excellent adhesion. Furthermore, this approach provides precise control over the chemical composition and thickness of the coating, ensuring consistent quality across the entire surface. However, uneven evaporation and ejection of molten metal droplets from the cathode during cathode arc deposition produce particles and droplets, resulting in an uneven coating surface. This study presents a new design for a magnetically controlled cathode arc source to effectively reduce particles and droplets during the cathodic arc deposition of multi-component alloy targets for nitride-based hard coatings. The study compares the performance of a new source with a conventional magnetic-controlled arc source for depositing TiAlNbSiN and AlCrSiN films. In the conventional source, the magnetic field is generated by a permanent magnet (PM), whereas in the new source, it is generated and controlled using an electromagnet (EM). Both films are produced using multi-component alloy targets (TiAlNbSi and AlCrSi) with identical composition ratios. The plasma characteristics of the two different arc sources are investigated using an optical emission spectrometer (OES), and the surface morphology, structural characteristics, deposition rate, uniformity, and surface roughness (Sa) are examined using scanning electron microscopy (SEM). When the EM was applied to have high plasma density, the hardness of the TiAlNbSiN film deposited with the novel arc source measured 31.2 ± 1.9 GPa, which is higher than that of the PM arc source (28.3 ± 1.4 GPa). In contrast, the AlCrSiN film created using a typical arc source exhibited a hardness of only 25.5 ± 0.6 GPa. This lower hardness may be due to insufficient ion kinetic energy to enhance stress blocking and increase hardness, or the presence of the h-AlN phase in the film, which was not detected by XRD. The electromagnet arc source, with its adequate ion bombardment velocity, facilitated a complementary effect between grain growth and stress blocking, leading to a remarkable hardness of 32.6 ± 0.5 GPa. Full article

This study investigates the role of Al alloying in tailoring the oxidation resistance of AlTiCrZrNbTa refractory high-entropy alloy (RHEA) coatings on Zry-4 substrates under high-temperature steam environments. Coatings with varying Al contents (0–25 at.%) were deposited via magnetron sputtering and subjected to oxidation tests at 1000–1100 °C. The results demonstrate that Al content critically governs oxidation kinetics and coating integrity. The optimal performance was achieved at 10 at.% Al, above which a dense, continuous composite oxide layer (Al₂O₃, TiO₂, Cr₂O₃) formed, effectively suppressing oxygen penetration and maintaining strong interfacial adhesion. Indentation tests confirmed enhanced mechanical integrity in Al-10 coatings, with minimal cracking post-oxidation. Excessive Al alloying (≥17 at.%) led to accelerated coating oxidation. This work establishes a critical Al threshold for balancing oxidation and interfacial bonding, providing a design strategy for developing accident-tolerant fuel cladding coatings. Full article

WMoTaNbV refractory high-entropy alloys (RHEAs) have received widespread attention due to their excellent low-temperature toughness, hardness, and wear resistance. In recent years, the rapid development of surface modification technology represented by laser cladding has provided a new technological path for RHEA surface forming, and at the same time put forward higher requirements for raw material powder. In this study, WMoTaNbV RHEA spherical powder was prepared by radiofrequency plasma spheronization, and then WMoTaNbV RHEA coating was prepared on the surface of Ti6Al4V (TC4) alloy by laser cladding technique. The experimental results show that the prepared alloy powders have very high sphericity and are almost free of agglomeration and oxidation. Coatings with laser powers of 3.1–3.9 kW (gradient setting of 2 kW) were tested, with the 3.3, 3.5, and 3.7 kW coatings showing the best of the abrasion resistance. The microhardness of the 3.3 kW, 3.5 kW, and 3.7 kW coatings was 1.72, 1.97, and 1.76 times higher than that of the substrate, and the wear resistance was 1.83, 3.42, and 2.13 times higher than that of the TC4 substrate, respectively. This experimental result shows that the surface hardness and wear resistance of WNbMoTaV RHEA coating can be effectively improved by precisely regulating the laser power, thus improving the surface hardness and friction and wear properties of TC4 titanium alloy. Full article

The Ti-6Al-4V alloy is widely used in orthopedic and dental implants due to its excellent mechanical, corrosion, and biological properties. However, it exhibits several limitations that can compromise its performance in clinical applications. Notably, the alloy suffers from a high coefficient of friction, which can lead to increased wear and reduced longevity of implants under relative movement conditions. Additionally, Ti-6Al-4V shows susceptibility to localized corrosion in physiological environments, particularly in the presence of bodily fluids that may result in the formation of pitting. These challenges underscore the need for surface modifications that can enhance the alloy’s tribological performance, thereby improving its overall efficacy and durability as a biomaterial in medical settings. In this context, the manuscript presents applied and innovative research that assesses the impact of implementing nanostructured Nb₂O₅ coatings through the reactive sputtering technique on the wear performance of Ti-6Al-4V alloy under both air and artificial saliva (AS) solution conditions using a Pin-on-Disk apparatus. The nanostructured Nb₂O₅ coating demonstrated the ability to reduce the wear rate and volume by up to 88% without inducing any modifications to the R_a and R_t of Ti-6Al-4V, a feature that is desirable for applications in implantable devices. The reduction in wear can be attributed to the shift from adhesive wear mechanisms on uncoated surfaces to abrasive mechanisms on coated surfaces. This research highlights the strategic advantage of utilizing Brazil’s abundant niobium resources to advance biomaterial technology and facilitate applications that benefit public health. Full article

Due to its excellent specific strength, corrosion resistance, and biocompatibility, titanium alloy is often used as a biological implant material. In order to address the issues of low hardness and poor wear resistance of the Ti-25Nb-3Zr-2Sn-3Mo titanium alloy, a TiN/Sn coating with good biocompatibility was deposited on its surface using a new composite modification technology of surface mechanical strengthening + surface mechanical coating. By taking advantage of the wear resistance of TiN and the adhesiveness of Sn, a composite coating with corrosion–wear resistance was formed to improve its corrosion–wear resistance. Using TiN/Sn powders of different ratios (10% Sn, 20% Sn, 30% Sn, and 40% Sn) as media, the alloy was subjected to a combined strengthening treatment of surface mechanical attrition and solid-phase coating under a nitrogen atmosphere. The microstructure and mechanical properties of the composite-strengthened layer were tested by means of XRD, SEM-EDS, a nanoindentation tester, a white-light interferometer, and a reciprocating wear tester. Moreover, the corrosion–wear properties of the samples under different loads and electrochemical conditions were analyzed. The results show that the surface composite-strengthened layer of the alloy consisted of a TiN/Sn coating + a mechanical deformed layer. With an increase in the Sn content, the thickness of the TiN/Sn coating continuously increased, while the thickness of the mechanical deformed layer continuously decreased. The composite-strengthened layer had good comprehensive mechanical properties. In the SBF solution, the corrosion–wear resistance of the composite-strengthened samples improved; the degree of wear first decreased and then increased with the increase in the Sn content, and it reached the optimal value when the Sn content was 30%. Compared with the raw sample, the corrosion of the coating sample increased, but the wear significantly decreased. The corrosion–wear synergy factor κ value first increased and then decreased with the increase in the Sn content, reaching a maximum value at the 20% Sn content. This is the result of the combined effect of the corrosion resistance and wear resistance of the coating. Full article

The article presents the results of a comparison of the wear resistance of coatings with a two-layer architecture (adhesion layer–wear-resistant layer) of Zr-ZrN, Zr-(Zr,Ti)N, Zr,Hf-(Zr,Hf)N, Zr,Nb-(Zr,Nb)N, Zr,Hf-(Ti,Zr,Hf)N, and Zr,Nb-(Ti,Zr,Nb)N coatings, deposited on a titanium alloy substrate. The wear resistance was studied using two different counterbodies: Al₂O₃ and steel. When in contact with the Al₂O₃ counterbodies, the best wear resistance was demonstrated by samples with Zr,Hf-(Zr,Hf)N and Zr,Nb-(Zr,Nb,Ti)N coatings. In tests conducted in contact with the steel counterbody, the best resistance was demonstrated by samples with Zr-ZrN and Zr,Hf-(Ti,Zr,Hf)N coatings. The wear resistance of samples with (Zr,Hf)N and (Zr,Nb,Ti)N coatings was 2.5–3.3 times higher than that of the uncoated sample. The Zr,Nb adhesion layer ensures better adhesion of the coating to the substrate. It was found that not only the adhesion strength of the adhesion layer to the substrate and coating is of significant importance but also the strength of the adhesion layer itself. The surface film of titanium oxide must be completely etched off to ensure maximum strength of the adhesive bond between the coating and the substrate. It has been established that the adhesion of the coating and the titanium substrate is also affected by the characteristics of the outer (wear-resistant) coating layer, which is the composition and structure of the wear-resistant coating layer. Delamination can occur both at the boundary of the adhesive layer with the substrate and at the boundary of the wear-resistant and adhesive layers of the coating depending on the strength of the adhesive bonds in the corresponding pair. It is necessary to ensure a good combination of properties both in the substrate–adhesion layer system and in the adhesion layer–wear-resistant layer system. Full article

The morphology and physicochemical properties of electrochemically deposited CaP coatings depend on the applied process parameters; however, the influence of different electrode systems has not been studied so far. In this work, the possibility of electrochemical deposition of CaP coatings on Ti6Al7Nb alloy using different electrode systems (two-electrode and three-electrode) and the influence of the electrode system and selected ranges of deposition parameters on the properties of the deposited CaP coatings were investigated. The morphology and physicochemical properties of the CaP coatings were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, X-ray diffraction (XRD), and corrosion studies. The results confirmed the effective electrodeposition of CaP coatings using both electrode systems. The applied electrode system and deposition parameters cause changes in the morphology of the obtained coatings. Chemical structure analysis confirmed the presence of mainly hydroxyapatite in the deposited CaP coatings. With the change in voltage/potential in a more cathodic direction, in addition to hydroxyapatite, a dicalcium phosphate dihydrate (DCPD) structure appears. The corrosion tests have shown that the applied deposition parameters have an impact on corrosion resistance and the deposited coatings exhibited protective properties against corrosion under physiological conditions. The CaP coatings with optimal properties for biomedical applications were deposited at a voltage of −4 V in the two-electrode system and a potential of −4 V_SCE in the three-electrode system. Full article

High-strength bolts are prone to crack initiation from the threaded hole during fastening due to large loads, which can compromise their performance and reliability. To enhance the durability of these bolts, coatings are often employed to strengthen their surfaces. NbMoTaW refractory high-entropy alloy coatings are widely used in hard coating applications due to their exceptional mechanical properties. However, the brittleness of this alloy at room temperature limits its performance in high-stress environments. To enhance the ductility of NbMoTaW alloys, this study systematically investigates the effect of varying titanium (Ti) content on the alloy’s properties. First-principles calculations were employed to analyze the elastic properties of TixNbMoTaW alloys, including elastic constants, the elastic modulus, the bulk modulus (B)-to-shear modulus (G) ratio (Pugh’s ratio), Poisson’s ratio (ν), and Cauchy pressure (C12–C44). The results indicate that the addition of Ti significantly improves the alloy’s plasticity. Specifically, when the Ti content is x = 2, the B/G ratio increases to 3.23, and Poisson’s ratio increases to 0.39, indicating enhanced deformability. At x = 0.75, the elastic modulus (E) increases to 273.78 GPa, compared to 244.99 GPa for the original alloy. The experimental results further validate the computational findings. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses indicate that all alloys exhibit a single body-centered cubic (BCC) phase. Room-temperature compression tests show that as the Ti content increases, the yield strength, fracture strength, and plasticity of the alloys significantly improve. Specifically, for a Ti content of x = 0.75, the yield strength reaches 1551 MPa, the fracture strength is 1856 MPa, and the plastic strain increases to 14.6%. For Ti1.5NbMoTaW, the yield strength is 1506 MPa, the fracture strength is 1893 MPa, and the plastic strain is 17.3%. Overall, TixNbMoTaW refractory high-entropy alloys demonstrate significant improvements in both plasticity and strength, showing great potential for coating applications in high-stress environments. Full article

Traditional binary coatings like TiN and CrN display limited thermal stability and wear resistance under extreme conditions. High-entropy alloy nitride (HEAN) coatings offer a promising solution due to their customizable composition and unique properties, including high hardness, corrosion resistance, and thermal stability. This study focused on (AlCrNbTaTi)N HEAN coatings to address a critical need for materials capable of enduring extreme mechanical and tribological demands by examining the impact of aluminum content on their structural and mechanical properties, providing insights for optimizing coatings in harsh conditions through a self-assembled nanolayer structure with enhanced resilience and performance. The coatings were deposited via a cathodic arc by employing an AlCrNbTaTi alloy target composed of aluminum (20, 50, 60, 70%) and equal molar ratios of Cr, Nb, Ta, and Ti. The coatings were characterized through grazing incidence X-ray diffraction, SEM, HR-TEM, a nano-indentation test, and a friction and wear test. The results indicated that with increasing Al content, the structure of (AlCrNbTaTi)N coatings shifted from FCC to an amorphous state, leading to a reduction in the hardness and elastic modulus, accompanied by an increase in the wear rate and friction coefficient. The (AlCrNbTaTi)N coating, with an equal atomic ratio of metallic elements, showed potential as a hard tool coating. It demonstrated outstanding mechanical and tribological properties, with a 34.5 GPa hardness, 369 GPa modulus, 0.35 friction coefficient, and 8.2 × 10⁻¹⁹ m²·N⁻¹ wear rate. The findings highlight the potential of (AlCrNbTaTi)N coatings to extend tool life and improve operational efficiency, helping advance materials engineering for industrial applications. Full article

Titanium (Ti) is widely used in structural, maritime, aerospace, and biomedical applications because of its outstanding strength-to-weight ratio, superior corrosion resistance, and excellent biocompatibility. However, the lower surface hardness and inferior wear resistance of the Ti and Ti alloys limit their industrial applications. Coating Ti surfaces can initiate new possibilities to give unique characteristics with significant improvement in the Ti component’s functionality. The current research designed and synthesized titanium nitride (TiN), titanium carbide (TiC), titanium carbonitride (TiCN), tantalum nitride (TaN), and niobium nitride (NbN) ceramic coating layers (400 µm) over a Ti substrate using a spark plasma sintering process (SPS). The coatings on the Ti substrate were compact and consolidated at an SPS temperature of 1500 °C, pressure of 50 MPa, and 5 min of holding time in a controlled argon atmosphere. Microstructure investigation revealed a defect-less coating-substrate interface formation with a transition/diffusion zone ranging from 10 µm to 20 µm. Among all of the ceramic coatings, titanium carbide showed the highest improvement in surface hardness, equal to 1817 ± 25 HV, and the lowest coefficient of friction, equal to 0.28 for NbN. Full article

Laser cladding, as an advanced surface modification technology, has the advantages of a high energy density, controlled dilution rate and good metallurgical bonding between the coating and the substrate. Its rapid heating and cooling properties help to form a dense and fine coating structure on the surface of the substrate, thus enhancing wear and corrosion resistance. In recent years, the in situ generation of carbide-reinforced iron-based composite coatings has gradually become a research hotspot because it combines the high hardness values of carbide with the high toughness values of iron-based alloys, which significantly improves the comprehensive performance of the coatings. This paper reviews the research progress of laser cladding in situ carbide-reinforced iron-based alloy coatings and explores the role of different types of in situ synthesized carbides (TiC, NbC, WC, etc.) in the coatings and their effects on their wear resistance and mechanical properties. The distribution of carbides in the coatings and their morphological characteristics are also discussed, and the effects of laser power, scanning speed and auxiliary treatments (ultrasonic vibration, induction heating, etc.) on the microstructure and properties of the coatings are analyzed. Finally, the problems and future directions of development in this field are envisioned. Full article

Currently, the main limitations of Pd-coated Nb-TiFe dual-phase alloys include insufficient hydrogen permeability, susceptibility to hydrogen embrittlement (HE), and poor tolerance of H₂S poisoning. To address these issues, this study proposes a series of improvements. First, a novel Nb₁₅Ti₅₅Fe₃₀ alloy composed of a well-aligned Nb-TiFe eutectic was successfully prepared using directional solidification (DS) technology. After deposition with a Pd catalytic layer, this alloy exhibits high hydrogen permeability of 3.71 × 10⁻⁸ mol H₂ m⁻¹ s⁻¹ Pa^−1/2 at 673 K, which is 1.4 times greater than that of the as-cast counterpart. Second, to improve the H₂S corrosion resistance, a new Pd₈₈Au₁₂ catalytic layer was deposited on the surface using a multi-target magnetic control sputtering system. Upon testing in a 100 ppm H₂/H₂S mixture, this membrane exhibited better resistance to bulk sulfidation and a higher permeance recovery (ca. 58%) compared to pure Pd-coated membrane. This improvement is primarily due to the lower adsorption energies of the former with H₂S, which hinders the formation of bulk Pd₄S. Finally, the composition region of the Pd-Au catalytic membrane with high comprehensive performance was determined for the first time, revealing that optimal performance occurs at around 12–18 at.% Au. This finding explains how this composition maintains a balance between high H₂ permeability and excellent sulfur resistance. The significance of this study lies in its practical solutions for simultaneously improving hydrogen permeability and resistance to H₂S poisoning in Nb-based composite membranes. Full article

(AlCrNbSiTiMo)N high-entropy alloy films with different nitrogen contents were deposited on tungsten carbide substrates using a radio-frequency magnetron sputtering system. Two different types of targets were used in the sputtering process: a hot-pressing sintered AlCrNbSiTi target fabricated using a single powder containing multiple elements and a vacuum arc melting Mo target. The deposited films were denoted as R_N0, R_N33, R_N43, R_N50, and R_N56, where R_N indicates the nitrogen flow ratio relative to the total nitrogen and argon flow rate (R_N = (N₂/(N₂ + Ar)) × 100%). The as-sputtered films were vacuum annealed, with the resulting films denoted as HR_N0, HR_N33, HR_N43, HR_N50, and HR_N56, respectively. The effects of the nitrogen content on the composition, microstructure, mechanical properties, and tribological properties of the films, in both as-sputtered and annealed states, underwent thorough analysis. The R_N0 and R_N33 films displayed non-crystalline structures. However, with an increase in nitrogen content, the R_N43, R_N50, and R_N56 films transitioned to FCC structures. Among the as-deposited films, the R_N43 film exhibited the best mechanical and tribological properties. All of the annealed films, except for the HR_N0 film, displayed an FCC structure. In addition, they all formed an MoO₃ solid lubricating phase, which reduced the coefficient of friction and improved the anti-wear performance. The heat treatment HR_N43 film displayed the supreme hardness, H/E ratio, and adhesion strength. It also demonstrated excellent thermal stability and the best wear resistance. As a result, in milling tests on Inconel 718, the R_N43-coated tool demonstrated a significantly lower flank wear and notch wear, indicating an improved machining performance and extended tool life. Thus, the application of the R_N43 film in aerospace manufacturing can effectively reduce the tool replacement cost. Full article