Titanium Alloy Surface Research Articles

Effect of Surface Modification of a Titanium Alloy by Copper Ions on the Structure and Properties of the Substrate-Coating Composition

To improve the strength properties, adhesion, and the thermal cycling resistance of ceramic coatings, the titanium alloy surface was modified with copper ions under different processing times. It is found that at the maximum processing time, the thickness of the alloyed layer reaches 12 μm. It is shown that the modified layer has a multiphase structure in addition to the main α and β–titanium phases with the intermetallic compounds of the Ti-Cu system. The parameters of the fine structure of the material are investigated by the X-ray diffraction analysis. It has been found that when the surface of the titanium alloy is modified, depletion occurs in the main alloying elements, such as aluminum and vanadium, the crystal lattice parameter increases, the root-mean-square (rms) displacements of the atoms decrease, and the macrostresses of compression arise. A multilevel micro- and nanoporous nanocrystalline structure occurs, which leads to an increase in the adhesion and the thermal cyclic resistance of the ceramic coating based on Si-Al-N.

Bioinspired antibacterial surface for orthopedic and dental implants.

Bacterial infections still present a significant concern in orthopedic and dental implant failure. Previous investigations have focused on modifying the surface texture, roughness, or coating implants with antibiotics to provide enhanced anti-bacterial properties. However, they have demonstrated limited success. In this study, we attempted to engineer the titanium (Ti) alloy surface biomimetically at the nano level using alkaline hydrothermal treatment (AHT) inspired by cicada's wing structure. Two modified surfaces of Ti plates were developed using 4 and 8-hr AHT at 230°C. We found that the control plates showed a relatively smooth surface, with little artifacts on the surface. In contrast, 4-hr AHT and 8-hr AHT plates showed nano-spikes of heights around 250-350 and 100-1,250 nm, respectively, that were distributed randomly all over the surface. We found a statistically significant (p < 0.05) number of non-viable cells for both S. aureus and P. aeruginosa bacterial strains when incubated for 1hr in a dynamic environment when compared with the control group. The 8-hr AHT groups killed 38.97% more S. aureus in static culture and 11.27% in a dynamic environment than the 4-hr AHT. Overall, the findings indicate that the nanostructures generated on titanium by the AHT showed significant bactericidal properties. We, therefore, recommend conducting alkaline hydrothermal treatment on the surfaces for future orthopedic and dental metallic implants.

Anti-Icing Characteristics of PTFE Super Hydrophobic Coating on Titanium Alloy Surface

Anti-icing is a technology urgently needed for human society to take production activities in high latitude and cold regions. Superhydrophobic coating is widely used to prevent important facilities from icing, such as power lines, building roof and aircraft skin. In this work, PTFE (PTFE, polytetrafluoroethylene) super hydrophobic coating was prepared on titanium alloy surface, a falling droplet impacted the PTFE super hydrophobic coating and froze on it. Then continuous freezing and thawing were carried out on the PTFE super hydrophobic coating. The result shows that the adhesion between PTFE super hydrophobic coating and droplet is extremely small. Droplet can bounce and roll along the surface, even at low temperatures. Freezing of droplet on PTFE super hydrophobic coating lasts 760 s, much longer than that of unmodified titanium alloy surface. Furthermore, the PTFE super hydrophobic coating has high wear resistance and can resist freezing and thawing permanently.

Characterization of a Macro- and Micro-Textured Titanium Grade 5 Alloy Surface Obtained by Etching Only without Sandblasting.

Our purpose was to physically characterize the surface, and the subsurface, of a macro- and micro-textured titanium grade 5 dental implant surface obtained by etching only, without sandblasting. The topography, surface roughness, as well as the surface structure and subsurface distribution of elements, were determined by scanning electronic microscopy (SEM), non-contact profilometry, X-ray diffraction (XRD), and a concentration profile performed by Auger electron spectroscopy (AES). The hydrogen concentration in the implants was measured; the ability to generate nanostructures when stored in deionized water was also investigated. Under SEM, the surface resembled a sandblasted and etched titanium surface with its typical macro- and micro-texture; roughness was moderate with average roughness (Sa) 1.29 µm. No titanium hydride was found at the implant surface and no enrichment of any alloying element was identified at the surface and subsurface. Hydrogen concentration was 79 ppm, within the normative tolerance (<130 ppm). After storage in water for 6 months, densely packed finger-like nanostructures were observed. The clinical advantage of this textured titanium alloy surface is that it displays the typical macro- and micro-features of a moderately rough sandblasted and etched (SLA) titanium surface without leaving behind any foreign sandblasting material.

Selected Physicochemical Properties of Diamond Like Carbon (DLC) Coating on Ti-13Nb-13Zr Alloy Used for Blood Contacting Implants.

Despite high interest in the issues of hemocompatibility of titanium implants, particularly those made of the Ti-13Nb-13Zr alloy, the applied methods of surface modification still do not always guarantee the physicochemical properties required for their safe operation. The factors that reduce the efficiency of the application of titanium alloys in the treatment of conditions of the cardiovascular system include blood coagulation and fibrous proliferation within the vessel’s internal walls. They result from their surfaces’ physicochemical properties not being fully adapted to the specifics of the circulatory system. Until now, the generation and development mechanics of these adverse processes are not fully known. Thus, the fundamental problem in this work is to determine the correlation between the physicochemical properties of the diamond like carbon (DLC) coating (shaped by the technological conditions of the process) applied onto the Ti-13Nb-13Zr alloy designed for contact with blood and its hemocompatibility. In the paper, microscopic metallographic, surface roughness, wettability, free surface energy, hardness, coating adhesion to the substrate, impendence, and potentiodynamic studies in artificial plasma were carried out. The surface layer with the DLC coating ensures the required surface roughness and hydrophobic character and sufficient pitting corrosion resistance in artificial plasma. On the other hand, the proposed CrN interlayer results in better adhesion of the coating to the Ti-13Nb-13Zr alloy. This type of coating is an alternative to the modification of titanium alloy surfaces using various elements to improve the blood environment’s hemocompatibility.

Influence of CeO2 addition on forming quality and microstructure of TiCx-reinforced CrTi4-based laser cladding composite coating

TiCx-reinforced CrTi4-based composite coatings were successfully fabricated on a Ti6Al4V titanium alloy surface via laser cladding technology by using coaxial Ti6Al4V/NiCr-Cr3C2 mixed powders with different CeO2 contents (0, 1, 2, 3, and 4 wt%). The influence of CeO2 addition on the forming quality, phase composition, microstructure, and elemental distribution of the laser cladded coatings was investigated via penetrant flaw detection, optical microscopy, X-ray diffraction, scanning electron microscopy, energy spectrum analysis, electro-probe microanalysis, and transmission electron microscopy. The results showed that CeO2 addition can inhibit the formation of cracks and pores. The least number of cracks and pores were observed upon the addition of 2 wt% and 3 wt% of CeO2, respectively. The phases in the coatings consisted of vacant titanium carbide (TiCx) and β solid solution (CrTi4). The morphologies of TiCx in the transition, cladding, and bonding zones exhibited distinct granular, dendritic, and short needle-like differences, respectively. Notably, the addition of CeO2 did not affect the phase composition, but it significantly influenced the content of dendritic TiCx. The dendritic TiCx content was minimum (35%) for a CeO2 content of 3 wt%. The dendritic TiCx was mainly enriched by Ti and C, and the content of C in primary dendrites was higher than that in secondary dendrites. The Ce and O atoms from CeO2 decomposition were recrystallised as CeO2 and Ce2O3, and distributed in the interphase boundary between TiCx and CrTi4, within the TiCx and CrTi4 grains, and at their grain boundaries. The Al, V, and Cr elements were uniformly distributed in the matrix phase (CrTi4), while elements Ni and Cr appeared segregated.

Influence of thermal oxidation on the properties of titanium alloys

In this study, the effect of thermal oxidation on the properties of the surface of titanium alloys was examined. Thermal oxidation was carried out at 750 °C within 6 hours, 800 °C within 5 hours, and 850 °C within 4 hours. Electrical resistance of the surface after thermal oxidation was measured. Metallographic analysis, microprobe analysis and X-ray phase analysis were carried out to determine the structure, chemical and phase compound of the oxide layer on the surface of titanium alloys after thermal oxidation. The results indicate that thermal oxidation leads to increase of electrical resistance of the surface of titanium alloys. Microstructural analysis showed that thickness of the oxide layer after thermal oxidation is in the range of 25 to 100 μm. Microprobe and X-ray phase analysis showed that TiO2 and Al2O3 oxides have the best impact on electrical resistance. Two variants of possible application of the results have been presented.

Investigation of the effect of the treatment of the surface of VT6 alloy on the penetration depth of implantable ions

The article presents studies on the combined treatment of VT6 titanium alloy, including preimplantation treatment of the titanium alloy surface with a laser or plasma and subsequent modification with highly efficient energy flows using a copper and iron cathode. The beneficial effect of preliminary surface laser and plasma treatments of VT6 alloy parts as an operation of preparing the surface for implantation on the mechanical and tribological properties, as well as the penetration depth of the implanted ions in the surface of the VT6 titanium alloy, is shown. This work was carried out as part of the state task of the Ministry of Science and Higher Education of the Russian Federation «The influence of magnetic fields and ion implantation on the structure, chemical composition and properties of titanium, aluminum alloys and elementary semiconductors».

Effect of Complex Magnetic-Abrasive and Chemical-Thermal Treatment on the Fatigue Resistance of VT8 Alloy Compressor Blades

The results of studies of the effect of complex magnetic-abrasive (MAT) and chemical-thermal (CTT) treatment on the fatigue resistance of compressor blades made of VT8 alloy are presented. The CTT method of the titanium alloy surface is a method of nitrocementation, which consists in the simultaneous saturation of the blade surface with carbon and nitrogen in a gas environment. Prior to that, MAT of blades were carried out to form favorable residual stresses in the surface layer, which stimulate the CTT process, provide its higher efficiency, productivity and the ability to create a diffusion layer of the required depth and quality. The results of measurements of microhardness of the surface layer of the blades in the initial state and after complex treatment are presented. The analysis of measurements showed that the microhardness of the initial blade tends to decrease steadily with small fluctuations to a depth of 0.25 mm, while on the blade after complex treatment by MAT+CTT+MAT we have three hardness peaks with higher values than the initial blades to a depth of 0.15 mm. The effect of complex treatment by technological cycle of MAT+CTT+MAT was estimated according to the results of comparative fatigue tests of VT8 alloy blades in the initial state and after treatment. It is shown that due to the formed reinforced layer on the surface of the blades after treatment, which has greater microhardness and microhardness gradient along the blade depth, the scattered damage accumulation under cyclic loading slows down, whereas the endurance limit of these blades based on N = 107 cycles is 14% higher than the endurance limit of the blades in the initial state.

Characterization of the Hydrogen Migration in a VT1-0 Titanium Alloy by Thermo-EMF and Eddy Current Nondestructive Control Methods

Abstract—The processes of hydrogen migration in a titanium plate and inhomogeneous hydrogen saturation are studied by measuring the thermopower and eddy currents. The processes of inhomogeneous hydrogen saturation of commercial-purity VT1-0 titanium are developed, tested, and investigated using these methods of nondestructive testing. To achieve an inhomogeneous hydrogen concentration in a titanium plate, a TiN film 1–2.6 μm thick is deposited onto it by magnetron sputtering, and the parts of the plate free of the film are hydrogenated. The thermo-emf and eddy currents are measured at various probe coordinates before and after hydrogen saturation of the plate. Eddy current testing demonstrates that, after the plate is hydrogen saturated for 1.5 h, the thermo-emf on the side of hydrogen sorption is significantly lower than on the coated side. After 144 h, a uniform thermo-emf ​​ distribution is obtained, as follows from eddy current measurements. The thermo-emf study is performed upon heating at a constant rate. The thermo-emf of each part of the titanium alloy surface (including the uncoated part) is approximately equal to the value obtained before hydrogenation. The electrical resistivity of the coated titanium plate at room temperature is approximately 0.315 mΩ cm. After hydrogenation, the hydrogen content in the uncoated part decreases slowly. The thermo-emf also decreases gradually. A hydrogen content distribution can be formed via a thermo-emf distribution ​​in the titanium plate. After holding for a sufficiently long time, a uniform thermo-emf distribution forms in the plate.

An experimental analysis of the influence of electrolyte compositions, current density and duration of the micro­arc oxidation process on the structural­phase state and properties of VT3­1 titanium alloy

It was determined that in an electrolyte containing 1.75 g/L KOH+1 g/L Na2SiO3+2 g/L NaAlO2, with an increase in current density from 15 A/dm2 to 50 A/dm2, the phase composition of the coating changes. In the three-phase state (aluminum titanate, rutile, and amorphous-like phase), with increasing j, instead of an amorphous-like phase, a crystalline mullite phase appears. The hardness of the coating increases from 5400 MPa to 12500 MPa. It was found that, in combination with aluminum titanate, mullite is the basis for achieving high hardness in the coating. The formation of a ceramic micro-arc oxide coating on the surface of the VT3-1 titanium alloy makes it possible to reduce the dry friction coefficient by more than 5 times to f=0.09.The effect of electrolysis conditions during micro-arc oxidation of the VT3-1 alloy (titanium-based) on the growth kinetics, surface morphology, phase-structural state, and physical and mechanical characteristics (hardness, coefficient of friction) of oxide coatings was studied. It was found that the process in the mode of micro-arc discharges is stably implemented on the VT3-1 alloy in an alkaline (KOH) electrolyte with additions of sodium aluminate (NaAlO2) and liquid glass (Na2SiO3). This makes it possible to obtain coatings up to 250 μm thick. In this case, a linear dependence of the coating thickness on the time of the MAO process is observed. The growth rate of the coating increases with increasing current density. The highest growth rate was 1.13 μm/min. It was revealed that in an electrolyte containing 1 g/L KOH+14 g/L NaAlO2 with an increase in the duration of oxidation from 60 to 180 minutes, the relative content of the high-temperature phase, rutile, increases. In the coatings obtained in the electrolyte 1.75 g/L KOH+1 g/L Na2SiO3+2 g/L NaAlO2, with an increase in the duration of the MAO process, the relative content of the amorphous-like phase decreases and the content of the crystalline phase of mullite (3Al2O3·2SiO2) increases

Bio-Inspired Design of Bi/Tridirectionally Anisotropic Sliding Superhydrophobic Titanium Alloy Surfaces.

Many biological surfaces with the multi-scale microstructure show obvious anisotropic wetting characteristics, which have many potential applications in microfluidic systems, biomedicine, and biological excitation systems. However, it is still a challenge to accurately prepare a metal microstructured surface with multidirectional anisotropy using a simple but effective method. In this paper, inspired by the microstructures of rice leaves and butterfly wings, wire electrical discharge machining was used to build dual-level (submillimeter/micrometer) periodic groove structures on the surface of titanium alloy, and then a nanometer structure was obtained after alkali-hydrothermal reaction, forming a three-level (submillimeter/micrometer/nanometer) structure. The surface shows the obvious difference of bidirectional superhydrophobic and tridirectional anisotropic sliding after modification, and the special wettability is easily adjusted by changing the spacing and angle of the inclined groove. In addition, the results indicate that the ability of water droplets to spread along parallel and perpendicular directions on the submillimeter groove structure and the different resistances generated by the inclined groove surface are the main reasons for the multi-anisotropic wettability. The research gives insights into the potential applications of metal materials with multidirectional anisotropic wetting properties.

Comprehensive Biological Evaluation of Biomaterials Used in Spinal and Orthopedic Surgery.

Biological acceptance is one of the most important aspects of a biomaterial and forms the basis for its clinical use. The aim of this study was a comprehensive biological evaluation (cytotoxicity test, bacterial colonization test, blood platelets adhesion test and transcriptome and proteome analysis of Saos-2 cells after contact with surface of the biomaterial) of biomaterials used in spinal and orthopedic surgery, namely, Ti6Al4V ELI (Extra Low Interstitials), its modified version obtained as a result of melting by electron beam technology (Ti6Al4V ELI-EBT), polyether ether ketone (PEEK) and polished medical steel American Iron and Steel Institute (AISI) 316L (the reference material). Biological tests were carried out using the osteoblasts-like cells (Saos-2, ATCC HTB-85) and bacteria Escherichia coli (DH5α). Results showed lack of cytotoxicity of all materials and the surfaces of both Ti6Al4V ELI and PEEK exhibit a significantly higher resistance to colonization with E. coli cells, while the more porous surface of the same titanium alloy produced by electron beam technology (EBT) is more susceptible to microbial colonization than the control surface of polished medical steel. None of the tested materials showed high toxicity in relation to E. coli cells. Susceptibility to platelet adhesion was very high for polished medical steel AISI 316L, whilst much lower for the other biomaterials and can be ranked from the lowest to the highest as follows: PEEK < Ti6Al4V ELI < Ti6Al4V ELI-EBT. The number of expressed genes in Saos-2 cells exposed to contact with the examined biomaterials reached 9463 genes in total (ranging from 8455 genes expressed in cells exposed to ELI to 9160 genes in cells exposed to PEEK). Whereas the number of differentially expressed proteins detected on two-dimensional electrophoresis gels in Saos-2 cells after contact with the examined biomaterials was 141 for PEEK, 223 for Ti6Al4V ELI and 133 for Ti6Al4V ELI-EBT. Finally, 14 proteins with altered expression were identified by mass spectrometry. In conclusion, none of the tested biomaterials showed unsatisfactory levels of cytotoxicity. The gene and protein expression analysis, that represents a completely new approach towards characterization of these biomaterials, showed that the polymer PEEK causes much more intense changes in gene and protein expression and thus influences cell metabolism.

Rapid apatite induction of polarized hydrophilic HA/PVDF bio-piezoelectric coating on titanium surface

Coatings with piezoelectric characteristics were prepared on the titanium alloy's surface to improve its biological properties, so that the titanium alloy possessed a piezoelectric effect similar to that of bones, thereby promoting bone growth and shortening bone repair time. Compared with other piezoelectric ceramic coatings, PVDF bio-piezoelectric coatings have better piezoelectric properties. However, the PVDF coating is hydrophobic, which is not conducive to calcium deposition. In this study, HA/PVDF coating was obtained on the titanium surface, which indicated a piezoelectric effect. The hydrophilicity of the coating has been improved with the increase of HA content. Corona poling gives the HA/PVDF coating piezoelectric characteristics, and also effectively reduces the contact angle. Moreover, the contact angle of the polarized HA/PVDF coating decreased by 66.9%. The synergistic effect of the introduction of HA and the high piezoelectric coefficient promotes the coating's mineralization. Surprisingly, the poled 20HA/PVDF coating surface was entirely covered by apatite after soaking in simulated body fluids (SBF) for 1 day with physiological loading. Additionally, the coating with rapid apatite deposition ability allows titanium alloy implants to obtain excellent biological activity, which has potential application value in the rapid repair of bone defects.

Promotion of tendon growth into implant through pore-size design of a Ti-6Al-4 V porous scaffold prepared by 3D printing

At present, no suitable method exists for tendon fixation after artificial prosthetic implantation. Researching and determining the optimal factors for biological fixation between the tendon and prosthesis is the crux for restoring limb function. In order to increase the growth of tendon fibers into the scaffold and reduce the formation of cicatricial tissue, selective laser melting (SLM) three-dimensional (3D) printing was used to prepare four types of cylindrical scaffold. The actual pore sizes of cuboids, which were used as the monomers, were 657.65, 527.15, 348.68, and 169.20 μm. Cell experiments showed that the greatest number of fibroblasts became adhered to and grew into the scaffold with an actual pore size of 527.15 μm. Each group of scaffolds was surgically implanted into a rabbit model of acute injury to the supraspinatus tendon. Micro-computed tomography (micro-CT) and hard tissue section staining were used to analyze the growth of tendon tissue in each group. We concluded that 527.15 μm is the best pore size for a titanium alloy surface to promote tendon ingrowth. The current study provides a reference for the clinical design of the pore size of tendon attachments onto the surfaces of tumor prostheses.

The influence of grit blasting and UV/Ozone treatments on Ti-Ti adhesive bonds and their durability after sol-gel and primer application

In this study, different surface pretreatments were applied to clean and activate titanium alloy surfaces. The samples were subjected to grit blasting treatments using two different pressures and afterwards, a UV/Ozone treatment was applied at different times to study the wettability and surface oxidation of the titanium samples. Scanning electron microscopy and laser confocal microscopy showed the surface morphology and the increased roughness with grit blasting pressure. X-ray Photoelectron Spectroscopy revealed that titanium was increasingly oxidized with increasing UV/Ozone treatment time, which leads to a reduced contact angle and a better adhesive performance in a butt tension test proving the effectivity of this surface treatment for titanium. Furthermore, the addition of sol-gel AC-120 and corrosion inhibition primer BR 6747 showed to be an additional improvement in the initial adhesion and after different degrees of aging by exposure to salt-spray, making the surface treatment techniques used in this research, a promising environmental friendly alternative to improve adhesive bonding performance.

The study of platelet reaction on a-C:H:SiOx coatings obtained via plasma enhanced chemical vapor deposition with bipolar bias voltage

Aim. To study platelet adhesion to a-C:H:SiO x film on titanium in an in vitro experiment to evaluate its antithrombogenic potential. Materials and methods. Thin (less than 1 μm) a-C:H:SiO x films were deposited on VT-6 titanium plates with a size of 10 × 10 mm 2 and a thickness of 0.2 mm using a vacuum ion-plasma unit using pulsed bipolar bias. The surface roughness was evaluated according to GOST 2789-73 using an atomic force microscope. The test samples were cultured at 37 °C for 30 min in platelet-rich human blood plasma, prepared for scanning electron microscopy, after which the distribution density of blood plates adhering to the test coating was calculated. Results. With the same roughness index of the studied a-C:H:SiO x samples, the film decreased 116 times (in comparison with untreated titanium) the platelet count per 1 mm 2 of the surface. Conclusion . The deposition of a-C:H:SiO x thin film on the surface of VT-6 titanium alloy by PACVD method using pulsed bipolar bias significantly reduces the distribution density of platelets in comparison with an untreated metal surface. In vitro data suggest a significant antithrombogenic potential of this type of coating on the surface of devices in contact with blood.

Modifications of Titanium and Zirconium Alloy Surfaces for Use as Dental Implants

The use of dental implants of titanium and its alloys has proved to be effective, through well established and documented parameters, both in the dimensions and in the manufacturing processes and also in the surgical techniques. There are clinical situations where there is a need to reduce the diameter of the implants, below 3.75 mm in diameter. In the current state of art of the implant technology it is desirable that these also have surfaces capable of decreasing the period of osseointegration. In the present work, to improve the mechanical strength of the material, an alloy of 80% of Ti and 20% of Zr % in mass was proposed and elaborated, aiming its use as biomaterial. Physical, chemical, microstructural and mechanical characterization was carried out. The surfaces of the treated samples were observed using: scanning electron microscopy (SEM); semi quantitatively chemically analyzed using dispersive energy spectroscopy (EDS: wettability of the samples was determined and, finally, the roughness was measured using optical profilometry. For the conditions used in the present work, it was concluded, that the best surface treatment for the TiZr 80/20 alloy was acid etching with 1% vol. hydrofluoric acid for 5 minutes, as this treatment presented the most prominent results of wettability and roughness simultaneously.

Osseoconduction of a sandblasted and etched titanium alloy surface in type IV bone: a human histologic evaluation

Osseoconduction of a sandblasted and etched titanium alloy surface in type IV bone: a human histologic evaluation

The effect of laser irradiation of the surface of VT6 titanium alloy on its microstructure, roughness and friction coefficient

The article discusses the technology of laser processing of VT6 titanium alloy as a technological operation to improve properties and structure. A promising direction for reducing roughness during laser hardening with reflow can be the development of a process using additives that reduce the surface tension of the melt and increase the wettability of the surface. It was revealed that phase hardening and martensitic transformation β → α are the causes of hardening of titanium during laser processing. This is confirmed by a change in the width of the x-ray lines. It was found that during laser processing with a speed of 3.7 mm/s and higher, a fine-grained structure is achieved.The results show that, at a sufficiently high cooling rate of the substrate, the grain sizes remain practically unchanged. Russian Federation “The influence of magnetic fields and ion implantation on the electrical structure and properties of titanium, aluminum alloys and elementary semiconductors”