Ti6Al4V Surfaces Research Articles

NiTi-SiC composite coating on Ti6Al4V alloy produced by SHS using induction heating

Abstract In this study, NiTi and NiTi-XSiC (1 wt%, 2 wt%, and 4 wt%) powders were coated on the Ti6Al4V surface by the self-propagating high-temperature synthesis (SHS) method using induction heating. Optic microscope and a scanning electron microscope (SEM) for the microstructural properties of coatings, energy dispersive spectrometry (EDS) for element distribution analysis, and X-ray diffractogram (XRD) for phase component analysis were carried out. The microhardness difference between the coating and the substrate was assessed by using the Vickers hardness scale. The microhardness increased with the addition of SiC, and the highest hardness value was 1416 Hv and detected in the sample NiTi–SiC 4 wt%. Phases formed by diffusion during solidification in the compounds Ti, Al, NiTi, NiTi2, NiAl, Ni3Al, Al3Ti, and TiO2, respectively.

Laser Com-Texture on Ti6Al4V Surface for Lubricant Transportation to Improve Tribological Properties

Abstract Artificial joint materials often wear out due to poor lubrication, affecting their service life. A compound texture (com-texture) was prepared, to improve the spreading of lubricant at the friction interface and reduce the friction and wear of artificial joint pairs UHMWPE and Ti6Al4V. The com-texture was divided into rough and smooth parts on the surface. The rough area was a hexagonal convex texture with a texture ratio of 66%, and it was covered with a recoagulated layer left by laser processing to absorb and transport lubricant to the friction interface. The smooth area was a convex texture with a texture ratio of 85%, which was the friction contact area. The texture morphology of the rough region was characterized by SEM and laser focusing microscope. It was found that the edge of the texture was covered with recondensed mountains after laser processing and corroded micro-nano pits, which helped to prepare super-hydrophilic surfaces. Besides, the flow law of simulated body fluid (SBF) on a textured surface was explored, and the motion process was recorded by a high-speed camera. The results showed that the com-texture could transport SBF to the friction region smoothly and quickly. The friction test results indicated that the structure had improved tribological properties.

Micro/nanoscale bioactive oxide coatings on Ti6Al4V fabricated by SLA and induction heating

Titanium (Ti)-based implants with micro/nano multiscale structures have been highlighted in dental and orthopedic fields due to the enhanced osteogenic abilities and mechanical interlocking. In this study, induction heating treatment (IHT) was developed to superimpose nano structure on microrough sandblasted and acid-etched (SLA) Ti6Al4V surface. The influences of SLA and IHT on the phase compositions, microstructures, properties, and formation mechanism of the coatings were explored. IHT for 12, 18 and 24 s realize the transformation of initially generated nanodot-like crystallites into a relatively uniform and high density of nanoscale protuberances. The oxide coating obtained by SLA + IHT has larger grains compared with that obtained by IHT separately. The nanoscale protuberances comprise crystalline rutile TiO2 and a small amount of α-Al2O3. IHT results in a successive increase of roughness on smooth surface with extension of IHT period, while samples induction heated for 18 and 24 s following SLA retain the initial microscale roughness of SLA surface. Since the larger porosity inside the oxide and local plastic deformation from SLA enhance adsorption and interaction ability of Ti6Al4V with oxygen, the thickness of oxide coating obtained by SLA + IHT increases to 861 nm compared with the 408 nm formed by IHT for 24 s. The micro/nano-structured oxide coating is in favor of improving the hydrophilicity of SLA surface in terms of the decreased contact angle from 129.4° to 69.1°, and shows good capability to induce hydroxyapatite deposition in simulated body fluid.

Study on strontium doped bioactive coatings on titanium alloys surfaces by micro-arc oxidation

In order to improve the bioactivity of titanium alloy, hydroxyapatite coatings with different amounts of Sr doping were prepared on the Ti6Al4V surface by micro-arc oxidation (MAO) using electrolytes containing Ca(CH3COO)2, NaH2PO4, and different concentrations of Sr(CH3COO)2, and EDTA-2Na was used as a complexing agent to complex Ca and Sr ions. The coatings' thickness, phase composition, microstructure morphology, and elemental distribution were examined, and the hydrophilicity and bioactivity were evaluated by contact angle and MC3T3-E1 preosteoblasts proliferation experiments. The results show that the concentration of Sr(CH3COO)2 in the electrolyte has little effect on the anodic oxide film breakdown voltage. However, the higher the concentration, the smaller the stable value of the MAO voltage is. The thickness of the MAO coating decreases with the increase of Sr concentration in the electrolyte, and the coatings mainly consist of strontium-containing hydroxyapatite, rutile, and anatase phases. The rise in Sr content leads to a decrease in Ca content, and both Ca and Sr content on the surfaces of the coatings are higher than that on the interior. (Ca + Sr)/P in all coatings is close to 1.67, which is similar to human bone. Moreover, all coating surfaces have good hydrophilicity, the Sr-doped MAO coatings promote the proliferation of MC3T3-E1 preosteoblasts, and the cell proliferation is higher on the coatings with higher Sr content.

Study of burr width and height using ANOVA in laser hybrid micro milling of titanium alloy (Ti6Al4V)

Ti6Al4V is regarded as the “workhorse” in aerospace industry for its wide applications at high temperatures. Unique attributes are high strength to density ratio and outstanding material properties at high thermal conditions. This present-day work involves the pre-slotting on Ti6Al4V surface with the help of fibre Laser, followed by the operation of micro-milling on respective Laser engraved slots. Localized melting due to Laser ablation leads to the decrease in the surface contact between milling tool and material surface. Micro-milling in return helps to remove the Heat affected zones (HAZ) created during Laser engraving process. ANOVA helps to point out the contributing factors for burr width and height on both milling sides. Main effect plots generated during process optimization, help to point out optimal combination of input parameters for minimized burr width and height. Higher frequency of Laser helps to generate consistent slots. Lower rotational speeds are responsible for high values of burr width and height. Whereas high rotational speed leads to efficient chip removal, resulting in decreased burr width and height.

Electric discharge assisted post-processing performance of high strength-to-weight ratio alloys fabricated using metal additive manufacturing

Metal additive manufacturing (MAM) is a near net shape fabrication process intended for producing complex and intricate shaped metallic parts/components. The feasibility in batch production as well as minimal material wastage establish the potential of MAM over other manufacturing methods. MAM of high strength-to-weight ratio alloys such as AlSi10Mg and Ti6Al4V is gaining popularity nowadays owing to their never ending demand in aerospace, automotive and biomedical industries. Both the alloys mark the two extreme ends of commercially available MAM alloys in terms of contrasting material properties. However, the poor surface integrity achieved by AlSi10Mg and Ti6Al4V parts/components after MAM demands post-processing via laser energy, chemicals, abrasives, conventional cutting tools etc. A recently developed low energy wire electrical discharge polishing (WEDP) method showed promising outcomes in MAM post-processing over aforementioned methods. In the present study, the performance and feasibility of WEDP in post-processing AlSi10Mg and Ti6Al4V are investigated with reference to the contrary properties associated with the alloys. The significant difference in melting point, thermal conductivity and chemical affinity led to distinct outcomes for the two alloys after WEDP. The enhancement in surface finish (Sa) was ~79% and ~91% for AlSi10Mg and Ti6Al4V respectively. The excellent corrosion resistance offered by the alloys is found to be unaltered in case of AlSi10Mg whereas enhanced for Ti6Al4V after WEDP. Modification in subsurface microhardness was observed upto 300 µm depth from polished surface for AlSi10Mg, whereas absent in Ti6Al4V. The study also revealed that the WEDP induced bigger craters in AlSi10Mg as well as cracks and resolidified layer in Ti6Al4V can be minimized at lower settings of pulse on time (T ON ). Moreover, EDS and XRD analysis indicated the formation of an oxide layer over Ti6Al4V surface after WEDP. • Wire electrical discharge polishing of high strength-to-weight ratio alloys having contrasting physical properties. • An in-depth surface integrity and corrosion behaviour analysis. • Polished surface analysis through detailed characterization methods. • Improvement in surface finish by ~79% and ~91% fData availabilityor AlSi10Mg and Ti6Al4V, compared to the as-built samples.

Extracting Mural and Volumetric Growth Patterns of Platelet Aggregates on Engineered Surfaces by Use of an Entity Tracking Algorithm.

Thrombosis is a major complication that can occur in both blood-contacting devices and regions and in regions of vascular damage. Microfluidic devices are popular templates to model various thrombogenic settings and to assess conditions that lead to bulk channel occlusion. However, area-averaged measurements miss the opportunity to extract real-time information on thrombus evolution and early dynamics of thrombus formation and propagation, which result in late-stage bulk channel occlusion. To clarify these dynamics, we have developed a standalone tracking algorithm that uses consecutive image connectivity and minimal centroid distance mappings to uniquely index all appearing thrombi in fluorescence time-lapse videos http://links.lww.com/ASAIO/A887 , and http://links.lww.com/ASAIO/A888 . This leads to measurements of all individual aggregates that can in turn be studied as ensembles. We applied tracking to fluorescence time-lapse videos http://links.lww.com/ASAIO/A887 , and http://links.lww.com/ASAIO/A888 of thrombosis across both collagen-functionalized substrate and across the surface of a roughened titanium alloy (Ti6Al4V) at a shear rate of 4000 s -1 . When comparing ensemble-averaged measurements to area-averaged metrics, we unveil immediate, steady thrombus growth at early phases on collagen surfaces and unstable thrombus attachment to roughened Ti6Al4V surfaces on Ti6Al4V surfaces. Additionally, we introduce tracked thrombus eccentricity and fluorescence intensity as additional volumetric measures of thrombus growth that relate back to the primary thrombosis mechanism at play. This work advocates for the complementation of surface macrostate metrics with characteristic thrombus microstate growth patterns to accurately predict critical thrombosis events.

Microstructure and Wear Resistance of FeCuNiTiAl High-Entropy Alloy Coating on Ti6Al4V Substrate Fabricated by Laser Metal Deposition

In order to improve the hardness and wear resistance of titanium alloys, an equimolar ratio high-entropy alloy (HEA) FeCuNiTiAl coating was fabricated on the surface of titanium alloy Ti6Al4V by means of laser metal deposition for the first time. The microstructure and composition of the HEA coating and the transition zone were observed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The results show that HEA coating and Ti6Al4V have suitable metallurgical bonding, and no defects, such as cracks, are found at the interface. The hardness of the HEA coating is between 450 and 500 HV0.5, which is about 1.5 times that of the Ti6Al4V substrate. Wear tests show that the wear rate of HEA coating is 0.89 × 10−5 mm3/(N·m), while that of Ti6Al4V reaches 53.97 × 10−5 mm3/(N·m), and the wear resistance of substrate is increased 60 times by the HEA coating. The wear mechanism of the Ti6Al4V substrate is mainly abrasive wear, and the wear mechanism of FeCuNiTiAl HEA coating is mainly adhesive wear, accompanied by slight oxidation wear and abrasive wear.

Formation, evolution and characterization of nanoporous structures on the Ti6Al4V surface induced by nanosecond pulse laser irradiation

Manipulating materials at nanoscale is challenging but rewarding. Nanostructures exhibit some unique properties distinguished from macroscopic bulk materials, so fabrication of nanostructures on the material surface is beneficial to broaden their functional applications. In this study, by nanosecond pulse laser irradiation in nitrogen atmosphere, it was found that unique nanoporous structures could be formed on the Ti6Al4V surface. The effects of laser parameters including the laser power, overlap rate, scanning speed, and repetition frequency on the formation and evolution of the nanoporous structures were systematically investigated. By changing the laser parameters, the nanoporous structures with various porosities could be easily achieved on the Ti6Al4V surface. According to the structural evolution and chemical composition, the formation mechanism of the nanoporous structures was discussed. Furthermore, by characterizing the micro-mechanical properties and wettability, it was found that the surface with nanoporous structures exhibited similar surface hardness but improved tribological performances compared to the original Ti6Al4V surface, and the surface wettability could be tuned. This study provides a simple method for fabricating nanoporous structures on the Ti6Al4V surface, which would broaden its functional applications.

Bioactive Titanium Surfaces Enriched with Silver Nanoparticles Through an In Situ Reduction: Looking for a Balance Between Cytocompatibility and Antibacterial Activity

This research aims toward an antibacterial and osteoconductive Ti6Al4V surface by chemical etching–oxidation treatment and in situ reduction of silver nanoparticles. Starting from a previously developed process, already proved to enhance the osteoinductive ability of titanium, different parameters are changed to tailor the amount of silver and its distribution across the surface oxide layer thickness. The samples are characterized by scanning and transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, release of silver, biofilm formation (Staphylococcus aureus), and cytocompatibility toward human osteoblasts progenitor cells. The total amount of silver in the surface oxide layer depends only on the concentration of the silver precursor. The time of the addition of the silver precursor, during the oxidation treatment, affects the oxide layer thickness, dimension, and distribution of the nanoparticles across the surface oxide: they are larger and accumulate on the outermost layer, if the addition occurs early. The maximum ion release occurs after 24 h and lasts up to 14 days; the later addition of silver precursors leads to sustaining the silver release for a longer time. The samples prepared with the higher concentration of the silver precursor are bactericide, but highly cytotoxic, whereas the other ones are bacteriostatic and moderately cytotoxic.

Determination of synergistic effect between roughness and surface chemistry on cell adhesion of a multilayer Si - Hydroxyapatite coating on Ti6Al4V obtained by magnetron sputtering

Ti alloys are widely used in the biomedical field because they have an adequate balance between mechanical properties, corrosion resistance and biocompatibility. However, when this material is incorporated in the human body, unfavorable reactions can be obtained which do not allow a good osseointegration due to the formation of a fibrous and non-adherent layer between the biomaterial and the bone, which can lead to failure or rejection of the implant. In this study, the influence of surface modification of Ti6Al4V alloy with a hydroxyapatite (HA) and silicon (Si) coating on its biological response in vitro was evaluated. The deposition process was performed by sputtering on two Ti6Al4V surfaces with different root mean square roughness values, the first one with 3.8 nm and the second one with 48.7 nm. The surface morphology of the coatings was observed by Scanning Electron Microscopy and Atomic Force Microscopy, the chemical composition was evaluated by X-ray Energy Dispersive Spectrometry and micro-Raman Spectroscopy. The in vitro biological response of the coatings was evaluated by cell metabolic activity assay and cell adhesion tests, using mouse mesenchymal stem cells. The control of the process parameters allowed obtaining a multilayer HA-Si coating with good compositional balance (Ca/P ratio very close to 1.67 and characteristic vibrations of the HA phase). Roughness values of 27 ± 5 nm and 52 ± 6 nm were obtained for the multilayer coatings obtained on Ti6Al4V (smooth surface) and Ti6Al4V (rough surface), respectively. Biological assays indicated a potentially non-toxic character of the coatings, moreover, the cell adhesion of Ti6Al4V was favored both by the incorporation of the HA-Si multilayer coating and by the increase in the roughness of the substrate.

Fabrication of Antireflective and Self-Cleaning Ti6Al4V Surface with Micro-Nano-Hierarchical Structures

Fabrication of Antireflective and Self-Cleaning Ti6Al4V Surface with Micro-Nano-Hierarchical Structures

Dual-functionalized titanium by ultrafast laser texturing to enhance human gingival fibroblasts adhesion and minimize Porphyromonas gingivalis colonization

Dental implant failure is primarily due to peri-implantitis, a consequence of bacterial penetration causing implant loosening. Beyond supporting the implant, the adhesion of gingival tissues to the surface is essential for its role as a physical barrier to bacteria. Surface nanotextures are widely known to affect wettability, protein adsorption, and cellular and/or bacterial adhesion. In this report, a femtosecond laser (fs-L) was used to design Laser-Induced Periodic Surface Structures (LIPSS) with Infra-Red (IR) or Green lasers on Ti6Al4V. Surface morphology, topography and wettability were characterized. Gingival fibroblasts adhesion was evaluated with sclerometer scratch tests and confirmed by ultrasonic bath cell detachment method. The fs-L texturing increases human gingival cells adhesion compared to polished surface. The adhesion of peri-implantitis associated bacteria was quantified. After 48 h of contact, IR LIPSS show antiadhesive properties for Porphyromonas gingivalis, whereas Green LIPSS, thanks to its smaller spatial period, have limited both Streptococcus mutans and Porphyromonas gingivalis adhesion. Thus, LIPSS generated on Ti6Al4V surfaces, especially Green LIPSS, are identified as having double biological functionality: repellent for bacteria and adhesive for gingival tissues. This study proves that fs-L processing is an innovative tool with potential to enhance implant success paving the way towards dual functionality.

Effects of Different Titanium Surface Treatments on Adhesion, Proliferation and Differentiation of Bone Cells: An In Vitro Study.

The objective of this study was to evaluate the impacts of different sandblasting procedures in acid etching of Ti6Al4V surfaces on osteoblast cell behavior, regarding various physicochemical and topographical parameters. Furthermore, differences in osteoblast cell behavior between cpTi and Ti6Al4V SA surfaces were evaluated. Sandblasting and subsequent acid etching of cpTi and Ti6Al4V discs was performed with Al2O3 grains of different sizes and with varying blasting pressures. The micro- and nano-roughness of the experimental SA surfaces were analyzed via confocal, atomic force and scanning electron microscopy. Surface free energy and friction coefficients were determined. hFOB 1.19 cells were seeded to evaluate adhesion, proliferation and osteoblastic differentiation for up to 12 d via crystal violet assays, MTT assays, ALP activity assays and Alizarin Red staining assays. Differences in blasting procedures had significant impacts on surface macro- and micro-topography. The crystal violet assay revealed a significant inverse relationship between blasting grain size and hFOB cell growth after 7 days. This trend was also visible in the Alizarin Red assays staining after 12 d: there was significantly higher biomineralization visible in the group that was sandblasted with smaller grains (F180) when compared to standard-grain-size groups (F70). SA samples treated with reduced blasting pressure exhibited lower hFOB adhesion and growth capabilities at initial (2 h) and later time points for up to 7 days, when compared to the standard SA surface, even though micro-roughness and other relevant surface parameters were similar. Overall, etched-only surfaces consistently exhibited equivalent or higher adhesion, proliferation and differentiation capabilities when compared to all other sandblasted and etched surfaces. No differences were found between cpTi and Ti6Al4V SA surfaces. Subtle modifications in the blasting protocol for Ti6Al4V SA surfaces significantly affect the proliferative and differentiation behavior of human osteoblasts. Surface roughness parameters are not sufficient to predict osteoblast behavior on etched Ti6Al4V surfaces.

Fabrication and droplet impact performance of superhydrophobic Ti6Al4V surface by laser induced plasma micro-machining

Titanium alloy Ti6Al4V super-hydrophobic surface plays a key role in enhancing the water repellency and anti-condensation of the fuselage. In this study, laser-induced plasma micromachining (LIPMM) is used for processing an array of cone-shaped protrusions on the surface with a micro-nano hierarchical structure. The relationship between surface wettability, micro-nano structure, and surface chemical composition was studied, meanwhile, the droplet impact behavior was experimented and simulated. The study found that with the aging treatment surface C element distribution and content increased significantly, and the wettability changed from superhydrophilic to hydrophobic. As the scan line spacing (50, 40, 30 μm) decreases, the contact angle increased and the hysteresis contact angle decreased. At 50 times and 30 μm line spacing, the contact angle 151.209°>150°, and the hysteresis contact angle 2.619°<10°. The collision experiments reveal that with the increase of the collision velocity (0.44 m/s to 0.98 m/s), the spreading diameter and the rebound height increases. The comparative results of experiments and simulations of collisions present that as the contact angle increases, the spreading diameter decreases, and the rebound height increases. Therefore, the LIPMM is feasible for the fabrication of a superhydrophobic surface and has a wide range of application prospects such as waterproofing, anti-fouling, and anti-icing.

Effectiveness of physicochemical techniques on the activation of Ti6Al4V surface with improved biocompatibility and antibacterial properties

Today, Ti6Al4V alloy is the most used and manufactured metallic implantable biomaterial in biomedical industry. However, in recent years it has demonstrated that Ti6Al4V based biomaterials could induce harmful diseases to human health in long-term implantations. Thus, biomedical community makes great efforts in order to improve the biocompatibility of Ti6Al4V implants and to afford additional antibacterial properties. For this, one promising strategy is the activation of Ti6Al4V surface through simple and industrially scalable physicochemical techniques that involve the increase of the thickness of the surface oxidation (TiO2) and the creation of active hydroxyl groups (Ti-OH). In this work, Ti6Al4V biomaterials were activated with chemical wet (CWT), electrochemical (ET), and physical oxygen plasma (POPT) treatments. Their surface activation effectiveness was evaluated in terms of surface damage, changes in surface roughness, wettability, and oxidation and hydroxylation capability (Ti-OH/TiO2 ratio). So, results show that acidic HCl:H2O2 piranha CWT of Ti6Al4V surfaces is the most effective surface activation procedure with improved surface reactivity (highest Ti-OH/TiO2 ratio), cytocompatibility, cell proliferation, and hemocompatibility. Antibiofilm activity of pristine Ti6Al4V was also enhanced by acidic HCl:H2O2 piranha treatment, leading to a decrease in bacterial adhesion of 30 % against S. aureus and E. coli.

Biocompatibility of micro/nano structures on the surface of Ti6Al4V and Ti-based bulk metallic glasses induced by femtosecond laser.

Femtosecond laser surface modification has been proved to be a versatile technology to create various functional materials by modifying solid surface properties. An interesting experimental phenomenon is found by exposing a Ti6Al4V alloy and Ti-based metallic glass to femtosecond laser irradiation. The research results show that the femtosecond laser induces different micro-nano structures on the surfaces of Ti6Al4V alloy and Ti-based metallic glass. Spherical structure and LIPSS (Laser-induced periodic surface structures) can be formed on the surface of Ti6Al4V alloy after femtosecond laser irradiation. On the surface of Ti-based metallic glass, LIPSS, SWPSS (Super-wavelength periodic surface structure) and neatly arranged microholes structures can be found. Under the same laser parameters, the micro-nano structures showed different evolution trends on the Ti6Al4V alloy and Ti-based metallic glass surfaces. The difference in surface structure between Ti6Al4V alloy and Ti-based metallic glass is since amorphous materials have no crystal lattice and a fixed melting temperature. In addition, there are differences in the biocompatibility of different surface structures. The size and distance of the micro-pits on the surface of different structures determine the ability of cells to adhesion, proliferate and differentiate. This conclusion has important significance for the application of Ti6Al4V alloy and Ti-based metallic glass in the field of biomedicine.

Microstructure and Wear Resistance of TiCp/Ti6Al4V Composite Coatings by Follow-Up Ultrasonic-Assisted Laser Additive Manufacturing

With the increasing demand for the high agility and fast response of high-level equipment in the aerospace and energy power fields, it is increasingly urgent to improve the performance of the high-temperature and wear resistance of the corresponding high-level components. Ceramic-reinforced titanium matrix composites have excellent high-temperature and wear resistance, but, in laser additive manufacturing, the primary ceramic phase is coarse, and the morphology of the ceramic phase is difficult to control, which limits their further development. In this investigation, a follow-up ultrasonic-assisted laser-additive-manufacturing method was proposed to prepare a 30 wt.% TiC/Ti6Al4V composite coating on a Ti6Al4V surface. Under the effects of ultrasonic cavitation and acoustic streaming, the content of the unmelted TiC was reduced, the dendritic primary TiC in the solidification process was broken and the distribution uniformity of the primary TiC was improved. The content of the unmelted TiC in the composite coating decreased significantly under ultrasonic action, and it was only 50.23% of that without ultrasonic action. At the same time, the average size of the dendritic primary TiC in the composite coating decreased from 61.59 μm to 27.04 μm, which was 56.10% smaller than that without ultrasonic action. The average microhardness of the composite coating reached the maximum of 656.70 HV0.2 under ultrasonic power, and it was 83.21% higher than that of the Ti6Al4V substrate, and 26.44% higher than that of the composite coating without ultrasonic power. Due to the ultrasonic-cavitation and acoustic-streaming effects, the content of the unmelted TiC obviously decreased, so that the average friction coefficient of the composite coating increased, and the wear mechanism changed from abrasive wear to adhesive wear.

Influence of Y2O3 addition on the microstructure of TiC reinforced Ti-based composite coating prepared by laser cladding

TiC reinforced Ti-based composite coatings were prepared on the Ti6Al4V surface via laser cladding with Ti6Al4V/NiCr-Cr 3 C 2 /Y 2 O 3 mixed powders. Influence of Y 2 O 3 on forming quality and microstructure of composite coatings was investigated systematically. The cracks were eliminated completely and the number of pores was drastically minimised when 2 wt% Y 2 O 3 was added. In addition, the reinforcement TiC and the matrix sloid solution β-Ti were the main precipitated phases within the coating. The addition of Y 2 O 3 inhibited the generation of Ti 2 Ni at the grain boundary, however, promoted the generation of Cr 1.93 Ti 1.07 in the coating. With the addition of Y 2 O 3 , the dendrites became largely developed and a large number of tertiary dendrites were found. Besides, a more obvious regional segregation appeared in the distribution of Ni and Cr elements in the coating with 2 wt% Y 2 O 3 . Furthermore, some nano-sized β-Ti were distributed on the surface of small TiC particles in both coatings. Combined with the theoretical analysis of the two-dimensional mismatch degree, the β-Ti and TiC interface exhibited a semi-coherent relationship. Therefore, β-Ti can nucleate with TiC as the heterogeneous nucleation matrix. In the meanwhile, there was a certain dependent growth relationship between the β-Ti and TiC. • Y 2 O 3 addition eliminated cracks completely and reduced porosity of the coating. • Y 2 O 3 addition led to sufficient growth of the developed dendrite TiC. • Irregular Ti 2 Ni disappeared and Cr 1.93 Ti 1.07 precipitated in coating with Y 2 O 3 . • Y 2 O 3 addition resulted in severe regional segregation of Cr and Ni. • β-Ti can nucleate with TiC as the heterogeneous nucleation center.

Construction of a Hierarchical Micro-/Submicro-/Nanostructured 3D-Printed Ti6Al4V Surface Feature to Promote Osteogenesis: Involvement of Sema7A through the ITGB1/FAK/ERK Signaling Pathway.

Constructing hierarchical hybrid structures is considered a facile method to improve the osseointegration of implants. Herein, a hierarchical micro-/submicro-/nanostructured surface feature of Ti6Al4V implants (3DAT group) was successfully constructed by combining the inherently formed three-dimensional (3D)-printed microscale topography, acid-etched sub-micropits, and anodized nanotubes. Compared with the classical SLA surface, the microscale topography and sub-micropits increased the three-dimensional space for the cell growth and mechanical stability of implants, while the modification of nanotubes dramatically improved the surface hydrophilicity, protein adsorption, and biomineralization. Most importantly, the 3DAT surface feature possessed excellent osteogenic performance in vitro and in vivo, with the involvement of semaphorin 7A (Sema7A) as revealed by RNA-seq through the ITGB1/FAK/ERK signaling pathway. The present study suggested that the hierarchically structured surface design strategy could accelerate the osseointegration rate of 3D-printed Ti6Al4V implants, promising personalized reconstruction of bone defects.