Ti6Al4V Substrates Research Articles

Wear and Corrosion Resistance of ZrN Coatings Deposited on Ti6Al4V Alloy for Biomedical Applications

Zirconium nitrides films were synthesized on Ti6Al4V substrates at a bias voltage of −50 V, −80 V, −110 V and −150 V by the direct current (DC) reactive magnetron sputtering technique. The as-deposited coatings were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The wear and corrosion resistance of the obtained ZrN coatings were evaluated to determine the possibility for their implementation in modern biomedical applications. It was found that the intensity of the diffraction peak of the Zr-N phase corresponding to the (1 1 1) crystallographic plane rose as the bias voltage increased, while the ZrN coatings’ thickness reduced from 1.21 µm to 250 nm. The ZrN films’ surface roughness rose up to 75 nm at −150 V. Wear tests showed an increase in the wear rate and wear intensity as the bias voltage increased. Corrosion studies of the ZrN coatings were carried out by three electrochemical methods: open circuit potential (OCP), cyclic voltammetry (polarization measurements) and electrochemical impedance spectroscopy (EIS). All electrochemical measurements confirmed that the highest protection to corrosion is the ZrN coating, which was deposited on the Ti6Al4V substrate at a bias voltage of −150 V.

Designing TiB2/Cr multilayer coatings on Ti6Al4V substrate for optimized wear resistance

The difference in mechanical properties between the TiB2 coating and the Ti6Al4V substrate can deteriorate the wear resistance of the TiB2 coating. To enhance the TiB2-based coating’s ability to deform in coordination with the ductile Ti6Al4V substrate and improve its tribological performance, the TiB2/Cr multilayer coatings were designed and deposited on Ti6Al4V substrates by magnetron sputtering. Results reveal that the FEM stress distribution of the TiB2/Cr multilayer coatings was optimized by varying the ceramic–metal thickness ratio (Q). As Q decreased from 1.0 to 0.5, the fracture toughness and adhesion strength of the coatings improved. The multilayer coating with Q = 0.5 exhibited the best toughness, crack propagation resistance (CPRs), and the smallest equivalent stress area, leading to a threefold enhancement in wear resistance compared to the TiB2 monolayer coating. However, further reduction of Q to 0.3 diminished wear resistance due to low hardness and significant stress concentration. Thus, there is an optimal balance between hardness, toughness, and stress distribution for achieving improved wear resistance in the multilayer design. Moreover, a notable correlation was observed between CPRs and the wear resistance of TiB2/Cr multilayer coatings.

Microstructural and Performance Analysis of (TiAl)95−xCu5Nix Coatings Prepared via Laser Surface Cladding on Ti–6Al–4V Substrates

In this study, the surface of (Ti-6Al-4V)TC4 alloy was modified via laser cladding. The elemental composition of the coating was (TiAl)95−xCu5Nix, with Ni as the variable (where x = 0, 3, 6, and 9 at.%). Multi-principal alloy coatings were successfully prepared, and their constituent phases, microstructures, and chemical compositions were thoroughly investigated. The hardness and wear resistance of the coatings were analyzed, and the compositions and interfacial characteristics of the different phases were examined via transmission electron microscopy. The analysis revealed that Ni formed a solid solution and a eutectic structure in the Ti(Al, Cu)2 phase. These findings provide valuable insights into the coating properties. Moreover, reciprocal dry sliding friction experiments were conducted to investigate the wear mechanism. The results revealed a significant increase in wear resistance owing to the formation of a Ni solid solution and changes in the coating structure. Additionally, tensile tests demonstrated that the tensile strength of the coatings initially increased and then decreased with varying Ni content. By combining these results with various analyses, we determined that the coating exhibited optimal properties at a Ni content of 6 at.%. Overall, this study comprehensively investigated the microstructure and phase transition behavior of these coatings through various analytical techniques. These findings provide valuable guidance for further optimizing both the preparation process and the performance of the coatings. The coatings exhibit excellent wear resistance and could inspire the design of more advanced protective surfaces.

Electrochemical characterization of TiO2 nanotubes formed on Ti6Al4V manufactured by PBF-EB or forging

AbstractThis study introduces the anisotropy effect of Ti6Al4V substrate obtained by electron beam melting (PBF-EB) on the anodizing process, revealing its capacity to induce anisotropic TiO2 nanotubes. Highly organized TiO2 nanotubes are formed on Ti6Al4V substrates produced through PBF-EB or forging, with the PBF-EB cross-orientation displaying superior nanotube growth due to enhanced catalytic activity. Morphological and electrochemical characterizations underscore the significant influence of substrate orientation and anodizing voltage on nanotube growth and corrosion resistance. PBF-EB-cross orientation at 30 V exhibits a thicker and more homogeneous nanotube layer, resulting in improved film resistance and substantially lower corrosion rates compared to forged substrates. The electrochemically calculated nanotube film thickness aligns with microscopic analyses, emphasizing the importance of a homogenous and resistive nanotube coating for effective corrosion control.

Surface Engineering of Ti6Al4V: Impact of Rhenium–Carbon Coatings with Molybdenum Anchors on Biocompatibility and Corrosion Behavior

Titanium alloys, particularly Ti6Al4V, are widely used in biomedical applications due to their excellent mechanical properties and inherent biocompatibility. However, enhancing their surface characteristics, such as biocompatibility and corrosion resistance, remains a key challenge for their long-term use in medical implants. In this study, we investigate the effects of rhenium–carbon coatings deposited on Ti6Al4V substrates via magnetron sputtering, incorporating a molybdenum anchoring layer. X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analyses confirmed the formation of rhenium carbides, elemental rhenium, and rhenium oxides within the coatings. Despite these successful depositions, scanning electron microscopy (SEM) revealed significant delamination and poor adhesion of the coatings to the Ti6Al4V substrates. Corrosion resistance, evaluated through potentiodynamic polarization tests, showed an increase in corrosion current densities and more negative corrosion potentials, indicating a detrimental effect on the substrate’s corrosion resistance. Biocompatibility assessments using PK15 cells demonstrated a marked decrease in cell viability and metabolic activity, particularly in samples with higher surface roughness. These findings underscore the critical need for the optimization of surface preparation and deposition processes to improve both the adhesion and biocompatibility of rhenium–carbon coatings on Ti6Al4V substrates. Future research should aim to refine coating technique to enhance adhesion, explore the mechanisms of cytotoxicity related to surface roughness, and expand biocompatibility studies across different cell lines and biological environments.

Evaluation of the immune response of peripheral blood mononuclear cells cultured on Ti6Al4V-ELI polished or etched surfaces.

While titanium and its alloys exhibit excellent biocompatibility and corrosion resistance, their polished surfaces can hinder fast and effective osseointegration and other biological processes, such as angiogenesis, due to their inert and hydrophobic properties. Despite being commonly used for orthopedic implants, research focuses on developing surface treatments to improve osseointegration, promoting cell adhesion and proliferation, as well as increasing protein adsorption capacity. This study explores a chemical treatment intended for titanium-based implants that enhances tissue integration without compromising the mechanical properties of the Ti6Al4V substrate. However, recognizing that inflammation contributes to nearly half of early implant failures, we assessed the impact of this treatment on T-cell viability, cytokine production, and phenotype. Ti6Al4V with extra low interstitial (ELI) content discs were treated with hydrofluoric acid followed by a controlled oxidation step in hydrogen peroxide that creates a complex surface topography with micro- and nano-texture and modifies the chemistry of the surface oxide layer. The acid etched surface contains an abundance of hydroxyl groups, crucial for promoting bone growth and apatite precipitation, while also enabling further functionalization with biomolecules. While cell viability remained high in both groups, untreated discs triggered an increase in Th2 cells and a decrease of the Th17 subset. Furthermore, peripheral blood mononuclear cells exposed to untreated discs displayed a rise in various pro-inflammatory and anti-inflammatory cytokines compared to the control and treated groups. Conversely, the treated discs showed a similar profile to the control, both in terms of immune cell subset frequencies and cytokine secretion. The dysregulation of the cytokine profile upon contact with untreated Ti6Al4V-ELI discs, namely upregulation of IL-2 could be responsible for the decrease in Th17 frequency, and thus might contribute to implant-associated bacterial infection. Interestingly, the chemical treatment restores the immune response to levels comparable to the control condition, suggesting the treatment's potential to mitigate inflammation by enhancing biocompatibility.

Ti6Al4V alloy with diamond particle-reinforced Cu-based coatings: Microstructure and tribological performance

To enhance the surface wear resistance of the Ti6Al4V alloy, diamond particles-reinforced Cu-based composite coatings (D500/D1000/D2000 coating: 500/1000/2000 mesh diamond: Cu-based alloy powder = 1:30 (wt%)) were fabricated by vacuum cladding. Cu-based alloys with liquid phase temperatures lower than the phase transition temperature of Ti6Al4V alloys were employed as cladding materials to avoid performance deterioration of Ti6Al4V substrates. The microstructure, mechanical properties, and dry-sliding tribological properties of the Cu-based composite coatings have been investigated systematically. The Cu-based composite coatings are composed of the ductile intermetallic compounds Ti3Sn and SnTi2 as the metal matrix, the hard and brittle intermetallic compounds CuTi, CuTi2, Ti(Cu, Al)2 and CuSn3Ti5, in situ generated TiC and the directly introduced diamond particle as the reinforced phases. In addition, a TiC hard phase protective layer was formed around the diamond particles, which retained the original properties of the diamond. The hardness of diamond particles-reinforced Cu-based composite coatings is much higher than that of the Ti6Al4V. Among them, the D2000 coating possesses the highest microhardness. The average Vickers hardness (HV0.5) on the coating surface and nanoindentation hardness (H) on the coating cross-section (the middle part without diamond particles) of the D2000 coating are 1329.8 HV0.5 and 16.87 GPa), which are 4–5 times higher than that of the Ti6Al4V substrate (333 HV0.5 and 3.37 GPa). Nevertheless, the D2000 coating (wear rate of 50.75 ×10−5 mm3/Nm) demonstrates slightly inferior tribological performance compared to the D500 coating. The wear rate of the latter is approximately 13.37 × 10−5 mm3/Nm, which is only 1/5.6 of the substrate (75.67 ×10−5 mm3/Nm). The larger the diamond particle size, the more the diamond serves as a bearing capacity support point to prevent the hard WC ball from further ploughing into the composite coating, and the better the wear resistance of the coating. Notably, D500 coating with excellent wear resistance has the potential for application in various fields of the machinery industry, marine engineering, and aerospace.

Effect of WC addition on microstructure and properties of laser melting deposited Ti6Al4V

Titanium alloys are generally characterized by low surface hardness, poor thermal conductivity, high friction coefficients and susceptibility to adhesive wear, which significantly hinder their industrial applications. To address this issue, we enhance the wear resistance of titanium alloys by incorporating nano WC particles. However, the optimal amount of WC to be added to titanium alloys remains unexplored. In this study, we prepared Ti6Al4V-xWC (wt%) (x = 0, 10, 20) coatings on Ti6Al4V substrates using laser melting deposition, specifically examining the effects of WC content on the microstructure and properties of the coating. The experimental findings indicate that the introduction of WC particles resulted in the formation of a TiC reinforced phase within the composite coating which promoted the equiaxialization of lamellae α phase. The hardness of the coatings increased significantly with the increase of the mass fraction of WC nanoparticles. Notably, the Ti6Al4V-10WC and Ti6Al4V-20WC coatings exhibited wear resistance that was 2.5 and 3.4 times greater, respectively, compared to the Ti6Al4V coatings. This enhancement in wear resistance can be attributed to the reinforcing phase (TiC) formed by the addition of WC. This experiment demonstrates a viable approach to improving the wear resistance of the Ti6Al4V titanium alloy through surface treatment.

Wear and neutron shielding resilience of titanium-hexagonal boron nitride coatings against extreme lunar radiation and thermal cycles

Ti6Al4V and Al6061 are aerospace alloys used in lunar structural components and rovers owing to their high specific strength. However, they deteriorate rapidly when subjected to demanding conditions of the lunar environment, such as extreme thermal cycles, solar particle radiation, and abrasive regolith. Cryo-milled powders were employed to deposit hBN-reinforced protective titanium coatings through plasma spray (atmospheric-APS and vacuum-VPS) with 2 and 10 vol% of hBN on Ti6Al4V and Al6061 substrates. These coatings were evaluated for durability under extreme lunar-like conditions, including thermal cycling, electron radiation, and synergistic (electron radiation-thermal cycle) exposure. The coatings exhibited radiation-induced hardening, resulting in a substantial increase in their microhardness ~20–40 % compared to virgin condition. Bright-field transmission electron microscopy (TEM) analysis reveals the presence of high dislocation densities, black dot defects, and dislocation clusters, providing evidence of the severe impact of synergistic environmental stresses. Ball-on-disk tribological tests were conducted in the presence of JSC-1 A lunar regolith simulant to evaluate the wear performance of coatings. Compared to conventional Ti6Al4V substrate, 50 %, 90 %, and 70 % reductions in wear volume were observed in the Ti/2 vol% hBN coatings in thermal-only, radiation-only, and synergistic environments. Neutron shielding tests indicate that the synergistic coatings offer higher neutron shielding performance by up to 28 % compared to virgin coatings, attributed to improved neutron capture by 10B isotopes. Upon a comprehensive assessment and ranking of multiple coatings under varying conditions, the VPS Ti/2 vol% hBN coating emerges as the top choice for protection against extreme radiation and thermal cycles for future lunar explorations.

Subcutaneous coding via laser directed energy deposition (DED-LB) for unalterable component identification

Part identification has become a priority in manufacturing, especially when it comes to the additive manufacturing (AM) industry, where the counterfeit printing of almost any digitalized component is possible. As a means of avoiding forgery, the development of non-detectable labels, or digital passports is necessary. In the present work, a novel methodology for printing subcutaneous coding on aeronautical parts is proposed thanks to the multimaterial capabilities of the laser based directed energy deposition (DED-LB). The coding is based on embedding a dot pattern of a high-density alloy on a small area of a lower density component, which once covered and finished generates a pattern only visible by X-ray imagining. The viability of the proposed methodology is proven by embedding WC particles on a Ti6Al4V substrate. Firstly, the most relevant process parameters are optimized to ensure a sharp and a readable code, and their geometry is analysed by means of industrial Computed Tomography (CT). Also, the metallurgical quality and chemical composition of the generated dots is evaluated by Scanning Electron Microscope (SEM). Finally, a demonstrator part is fabricated with a hidden code. The code readability and the mechanical properties are tested to ensure the feasibility of the developed methodology.

Enhanced mechanical, corrosion, and tribological properties of hydroxyapatite coatings for orthopedic and dental applications

Biomedical coatings were elaborated by pulsed electrodeposition with hydrogen peroxide (H2O2) into electrolytes on Ti6Al4V substrates, and the effect of H2O2 concentration on the electrolyte and the heat treatment was studied. The experimental procedures employed in this study produce a consistent hydroxyapatite coating. This coating is well-suited for use in bio-implants, as it enhances the integration of the implant with surrounding bone tissue and improves the mechanical performance. The coatings' surface morphology and chemical composition were assessed using scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDXS) for x-ray microanalysis. X-ray diffraction (XRD) was also utilized to identify the phases and composition of the coatings. Nanoindentation and scratch tests were conducted to analyze the nanomechanical properties and adhesion behavior. Potentiodynamic polarization was employed in the Ringer solution to evaluate the corrosion resistance and replicate the conditions of the human body environment. The results of our thorough investigation revealed that employing pulsed electrodeposition with 9 % H2O2 in the electrolyte, combined with subsequent heat treatment, facilitated the creation of coatings comprising two distinct phases: stoichiometric hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP). Our meticulous research underscores the significance of this process in achieving these specific coating compositions. Under these tests listed above, this composite demonstrated favorable mechanical properties (E = 30.45 GPa and H = 72.2 MPa). It also exhibited superior scratch adhesion and a critical load of 23 MPa and 12 N, respectively. Additionally, an improvement in tribological comportment was observed, and the wear volume decreased from 4.15 106 μm3 to 2.44 106 μm3. The HAP coating heat treated with 9 % H2O2 exhibited the highest corrosion resistance, with Ecorr at −0.189 V/SCE and icorr at −1.11 μA cm−2

Double laser two-step process for creating interconnected frame microstructures' superhydrophobic surface with dual scales

Superhydrophobic surfaces have garnered significant attention for their unique wettability and extensive applications across various critical fields. In this paper, a two-step laser processing technique, involving infrared nanosecond laser patterning and ultraviolet picosecond laser surface modification, was employed to fabricate interconnected frame surfaces with dual-scale microstructures on Ti6Al4V substrates. After that, the microstructure surface was chemically modified with 1H,1H,2H,2H-perfluorodecyl trimethoxy-silane to achieve a superhydrophobic surface. An L32 (47) orthogonal experiment was used to analyze the effect of seven main factors (including the structure size, scanning velocity and the fluence, number of scans of infrared nanosecond laser and ultraviolet picosecond laser) on the wettability of the interconnected frame microstructures surface. After optimization, the surface strongly corresponded with the Cassie-Baxter model and demonstrated a water contact angle of 153.22±1.64° and roll-off angle of 4.43±1.70°. The experiments demonstrated that the optimized surface possesses excellent mechanical stability and corrosion resistance. Additionally, the optimized surface exhibits anti-adhesion, effective self-cleaning, and anti-fouling properties, which hold promise for addressing issues of liquid adhesion and dust pollution in industrial machinery.

Tribological behavior of MoS2–Sb2O3-annealed nanodiamond coating on PEO-LST treated Ti6Al4V

MoS2–Sb2O3 coating is commonly used as solid lubricant for titanium alloys, but the wear-resistance performance is still limited. Core-shell annealed nanodiamond (AND) particle is used as reinforcement for MoS2–Sb2O3 coating on Ti6Al4V substrate treated by plasma electrolytic oxidation (PEO) and laser surface texturing (LST). The incorporation of AND particles into the MoS2–Sb2O3 coating results in a 39 % decrease in friction and significantly reduces wear on the composite coating. Structural transformation of AND particles to amorphous carbon and graphitic structure promotes the densification of top-layer coating, enhancing lubrication and wear-resistance. Change of contact stress by PEO-LST promotes the formation of dense tribofilm and re-orientation of MoS2. This study has implications for the development of solid lubrication coatings for aerospace applications through functional nanomaterials and targeted designed surfaces.

DLC FILMS ON Ti6Al4V SUBSTRATES OF NANOINDENTATION, SURFACE ROUGHNESS FOR LASER POWDER BED FUSION WAS PERFORMED UTILIZING ORTHOPEDIC IMPLANT MATERIALS

Diamond-like carbon (DLC) films on titanium alloy Ti6Al4V substrates were tested with nanoindentation and surface roughness to look at the hardness and roughness of the coating and substrate systems as well as their mechanical properties. The powdered titanium alloy Ti6Al4V used in the substrate specimen was produced using laser powder bed fusion, an additive manufacturing process. In this study, we investigated the influence of substrates on the nanoindentation and surface roughness of the DLC film layer with an estimated [Formula: see text]m thickness on Ti6Al4V substrates. The findings of the nanoindentation show that the reaction to the impact was more flexible than expected. Maximum load, residual nanoindentation depth, hardness, and modulus may influence mechanical properties. The DLC-film Ti6Al4V substrate materials’ top surface roughness is measured. As a result of the increased load-carrying ability of DLC/Ti6Al4V, Ti6Al4V is a superior choice for substrate materials for DLC films, A DLC coating, measuring [Formula: see text] m in thickness, was applied to a Ti6Al4V substrate utilizing a 5-min chromium deposition process. The biocompatibility of the substrates plays a crucial role in determining the DLC films capacity to prolong the lifespan of bone implants.

Effect of Co-Sputtered Copper and Titanium Oxide Coatings on Bacterial Resistance and Cytocompatibility of Osteoblast Cells.

One of the primary risk factors for implant failure is thought to be implant-related infections during the early healing phase. Developing coatings with cell stimulatory behaviour and bacterial adhesion control is still difficult for bone implants. This study proposes an approach for one-step deposition of biocompatible and antimicrobial Cu-doped TiO2 coatings via glow-discharge sputtering of a mosaic target. During the deposition, the bias of the Ti6Al4V substrates was changed. Structure examination, phase analysis, and surface morphology were carried out using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The hardness values and hydrophilic and corrosion performance were also evaluated together with cytocompatible and antibacterial examinations against E. coli and S. aureus. The results show great chemical and phase control of the bias identifying rutile, anatase, CuO, or ternary oxide phases. It was found that by increasing the substrate bias from 0 to -50 V the Cu content increased from 15.3 up to 20.7 at% while at a high bias of -100 V, the copper content reduced to 3 at%. Simultaneously, apart from the Cu2+ state, Cu1+ is also found in the biased samples. Compared with the bare alloy, the hardness, the water contact angle and corrosion resistance of the biased coatings increased. According to an assessment of in vitro cytocompatibility, all coatings were found to be nontoxic to MG-63 osteoblast cells over the time studied. Copper release and cell-surface interactions generated an antibacterial effect against E. coli and S. aureus strains. The -50 V biased coating combined the most successful results in inhibiting bacterial growth and eliciting the proper responses from osteoblastic cells because of its phase composition, electrochemical stability, hydrophilicity, improved substrate adhesion, and surface roughness. Using this novel surface modification approach, we achieved multifunctionality through controlled copper content and oxide phase composition in the sputtered films.

Study on the sand erosion resistance of ZrN and ZrAlSiN coatings

Brittle spalling is a crucial problem for hard ceramic coatings under high-angle sand erosion, especially for traditional binary nitride coatings such as ZrN. Here, we deposited the ZrAlSiN coating by co-doping Al and Si into the ZrN coating to improve the toughness and erosion resistance. ZrN coating was also prepared on Ti6Al4V substrates by magnetic filtration cathode vacuum arc technology (FCVA) under the same process for contrast. The microstructure, mechanical properties, and sand erosion resistance of ZrN and ZrAlSiN coatings were studied. The ZrAlSiN coating contains nanocrystalline ZrAlN and amorphous Si3N4. The results show that the ZrAlSiN coating exhibits the highest H, H/E, H3/E2, and Welastic/Wplastic among as-deposited coatings with the value of ~30.8Gpa, ~0.12, ~0.43Gpa, and 2.19, respectively. The erosion rate of the ZrAlSiN coating is about half that of the ZrN coating. The dopping of Si element is conducive to inhibition of the grain growth. The enhanced toughness while maintaining high hardness is one of the main reasons for the better anti-sand erosion performance of ZrAlSiN coatings. The research helps promote the application of ZrN-based coatings in the field of anti-sand erosion.

Corrosion behavior of TiN monolayer and CrN/TiN multilayer coatings: Impact of immersion time and saline solution type

AbstractThe corrosion behavior of the TiN monolayer and CrN/TiN multilayer coatings deposited via cathodic arc evaporation physical vapor deposition (CAE‐PVD) on the Ti–6Al–4V substrates were evaluated in Ringer's and Hank's physiological saline electrolytes. XRD (x‐ray diffractometry) and scanning electron microscopy (SEM) analysis were used to characterize the coatings. The corrosion behavior of coatings was assessed by impedance spectroscopy and potentiodynamic polarization techniques. The results showed that the corrosion resistance of coatings was increased in the order of TiN‐Ringer's < TiN‐Hank's < CrN/TiN‐Ringer's < CrN/TiN‐Hank's. Therefore, it can be concluded that the CrN/TiN coating, due to having a large number of interfaces and a smoother surface with fewer macroparticles and pinholes, is more efficient in raising the corrosion resistance properties of titanium than TiN monolayer coating. Moreover, it was observed that Ringer's solution is a more severe environment than Hank's solution. Both coatings, because of the precipitation of a protective corrosion products layer on their surface, showed an enhancement in corrosion resistance with increasing the immersion time from 1 to 14 days in Hank's. The results suggest TiN monolayer and CrN/TiN multilayer coatings as promising candidates for biomedical applications.

Oxidation resistance, corrosion behavior and grinding performance of laser-deposited TaMoCrTiAl refractory high-entropy coating

In this study, TaMoCrTiAl refractory high-entropy alloy coating without defects was successfully prepared on the Ti6Al4V substrate by laser metal deposited. Microstructure and properties were investigated systematically by multiple characterization methods. The results of phase and morphology experiments indicate that the coating comprised a BCC phase and a partial Laves phase. The coating, with an average thickness of 990 μm, exhibits good metallurgical bonding with the substrate. Further observation reveals that the cladding region consists of irregular bulk crystals. The heat-affected zone has a fine grain size, whereas the substrate has coarse and uneven grains. The high-temperature oxidation test shows that the formation of an Al2O3 oxide layer enhances the coating's high-temperature oxidation resistance. According to the results of microhardness tests, the average microhardness in the coating is about 570.98 HV (1.87 times that of the substrate) due to the formation of the leave phase particles and the fine-grain strengthening. The presence of Titanium, chromium and molybdenum elements in the coating facilitates the formation of a passivation film, thereby enhancing its corrosion resistance. Furthermore, the coating exhibits the smallest grinding force (43.637 N) and the lowest roughness (0.506 μm) at an experimental temperature of 100 °C, which demonstrates that appropriately elevating the experimental temperature can decrease the grinding force and enhance the flatness of the grinding surface.

In-vitro biocompatibility, antibacterial activity, and corrosion resistance of HA-TiO2/ZnO coating fabricated by plasma electrolytic oxidation on Ti6Al4V

The hydroxyapatite/Zinc Oxide (HA-TiO2/ZnO) coatings were grown on the Ti6Al4V substrate by plasma electrolyte oxidation from the CaP-based electrolyte containing 1, 3, and 6 g/L ZnO nanoparticles. XRD results confirmed the presence of ZnO, HA, and rutile phases in all coatings. According to SEM observations, coatings presented the porous morphology as a result of micro-arc discharges during the PEO process, whereas some of the pores in the composite coatings were filled by ZnO proportional to its content. After 7 days of immersion in SBF solution, accumulations of bone-like clusters were visible on the surface, demonstrating a promising bio-mineralization ability for all coatings, although the higher amount of 6 g/L ZnO had partially an inhibitory effect on the apatite nucleation. In-vitro studies demonstrated a time and concentration-dependent impact of ZnO on the viability of MG-63 osteoblast-like cells so that the concentration of 3 and 6 g/L caused the death of some cells after 7 days. The antibacterial tests also showcased that the presence of ZnO decreased the activity of gram-negative bacteria (E. coli) and gram-positive bacteria (S. aureus), while the higher concentration of ZnO particles led to more antibacterial activity of the coating. Finally, evaluating the corrosion behavior of PEO coatings through a potentiodynamic polarization test in Ringer's solution manifested a better protection against corrosion by increasing the ZnO content in the coating, mainly owing to the blocking of the pores by the ZnO particles, and as a result, the greater difficulty of electrolyte to reach the titanium substrate.

Fabrication and evaluation of Ti6Al4V /NiCrBSi bimetallic structure with Nb/Cu bilayer by laser melting deposition

The fabrication of high-quality bimetallic structures using titanium and nickel alloys is a desirable integration for fully leveraging their remarkable properties. This study is dedicated to the surface modification of titanium brake discs, using laser melting deposition to produce the Ti6Al4V/NiCrBSi bimetallic structure and inhibition of brittle phase formation by Nb/Cu bilayer. The results showed the generation of brittle intermetallic compound phases was effectively resisted using Nb/Cu bilayer, thus preventing cracking and peeling of the Ti6Al4V substrate and NiCrBSi coatings. Moreover, the bimetallic structure fractured at the weakest position, i.e. at the Nb/Cu interface, with a maximum strength of 243.20 ± 55.16 MPa during the tensile testing, exhibiting brittle-like failure behaviour. Additionally, the friction and wear properties of the Ti6Al4V substrate and NiCrBSi coatings were evaluated at both room temperature and elevated temperature (600 °C). The results reveal that the NiCrBSi coatings effectively improved the friction and wear properties of the Ti6Al4V.