Search Results (878)

Background: The implant–abutment interface has been thoroughly examined due to its impact on the success of implant healing and longevity. Removing the abutment is advantageous, but it changes the biomechanics of the implant fixture and restoration. This in vitro three-dimensional finite element analytical (FEA) study aims to evaluate the distribution of von Mises stress (VMS) in abutment-free and three additional implant abutment connections composed of various titanium alloys. Materials and methods: A three-dimensional implant-supported single-crown prosthesis model was digitally generated on the mandibular section using a combination of microcomputed tomography imaging (microCT), a computer-assisted designing (CAD) program (SolidWorks), Analysis of Systems (ANSYS), and a 3D digital scan (Visual Computing Lab). Four digital models [A (BioHorizons), B (Straumann AG), C abutment-free (Matrix), and D (TRI)] representing three different functional biomaterials [wrought Ti-6Al-4Va ELI, Roxolid (85% Ti, 15% Zr), and Ti-6Al-4V ELI] were subjected to simulated static/cyclic static loading in axial/oblique directions after being restored with highly translucent monolithic zirconia restoration. The stresses generated on the implant fixture, abutment, crown, screw, cortical, and cancellous bones were measured. Results: The highest VMSs were generated by the abutment-free (Model C, Matrix) implant system on the implant fixture [static (32.36 Mpa), cyclic static (83.34 Mpa)], screw [static (16.85 Mpa), cyclic static (30.33 Mpa), oblique (57.46 Mpa)], and cortical bone [static (26.55), cyclic static (108.99 Mpa), oblique (47.8 Mpa)]. The lowest VMSs in the implant fixture, abutment, screw, and crown were associated with the binary alloy Roxolid [83–87% Ti and 13–17% Zr]. Conclusions: Abutment-free implant systems generate twice the stress on cortical bone than other abutment implant systems while producing the highest stresses on the fixture and screw, therefore demanding further clinical investigations. Roxolid, a binary alloy of titanium and zirconia, showed the least overall stresses in different loadings and directions. Full article

In additively manufactured (AM) Ti-6Al-4V, the role of martensitic α′ in governing brittleness versus toughness remains debated, largely because complex thermal histories and other intertwined physical factors complicate interpretation. To isolate and clarify the intrinsic effect of cooling rate, we employed a Gleeble thermal simulator, which enables precisely controllable cooling rates while simultaneously achieving ultra-fast quenching comparable to AM (up to ~7000 °C/s). By varying the cooling rate only, three distinct microstructures were obtained: α/β, α_m/α′, and fully α′. Compression tests revealed that the ultra-fast-cooled fully martensitic Ti-6Al-4V attained both higher strength and larger fracture strain, with densely distributed elongated dimples indicative of ductile failure. Three-dimensional microstructures reconstructed from microscopy, analyzed using an EVP-FFT crystal plasticity model, demonstrated that refined α′ laths and abundant high-angle boundaries promote more homogeneous strain partitioning and reduce stress triaxiality, thereby delaying fracture. These results provide potential evidence that extreme-rate martensitic transformation can overcome the conventional strength–ductility trade-off in Ti-6Al-4V, offering a new paradigm for processing titanium alloys and AM components with superior performance. Full article

Osseodensification (OD) has emerged as a favorable osteotomy preparation technique that preserves and compacts autogenous bone along the osteotomy walls during site preparation, enhancing primary stability and implant osseointegration. While OD has demonstrated promising results in low-density trabecular bone, especially when used in conjunction with acid-etched (AE) implant surfaces, its efficacy in high-density cortical bone remains unclear—particularly in the context of varying implant surface characteristics. In this study, Grade V titanium alloy implants (Ti-6Al-4V, 4 mm × 10 mm) with deep threads, designated bone chambers and either as-machined (Mach) or AE surfaces were placed in 3.8 mm diameter osteotomies in the submandibular region of 16 adult sheep using either OD or conventional (Reg) drilling protocols. Insertion torque values (N·cm) were measured at the time of implant placement to evaluate primary stability. Mandibles were harvested at 3-, 6-, 12-, or 24-weeks post-implantation (n = 4 sheep/time point), and histologic sections were analyzed to quantify bone-to-implant contact (BIC) and bone area fractional occupancy (BAFO). Qualitative histological analysis confirmed successful osseointegration among all groups at each of the healing time points. No statistically significant differences were observed between OD and conventional drilling techniques in insertion torque (p > 0.628), BIC (p > 0.135), or BAFO (p > 0.060) values, regardless of implant surface type or healing interval. The findings indicate that neither drilling technique nor implant surface treatment significantly influences osseointegration in high density cortical bone. Furthermore, as the osteotomy was not considerably undersized, the use of OD instrumentation showed no signs of necrosis, inflammation, microfractures, or impaired osseointegration in dense cortical bone. Both OD and Reg techniques appear to be suitable for implant placement in dense bone, allowing flexibility based on surgeon preference and clinical circumstances. Full article

Accurate temperature measurement is a key parameter that determines the quality of additive manufactured components in directed energy deposition processes. Optical pyrometers which are used to provide in-process temperature data require accurate emissivity data of the metal surface. Process-specific emissivity data for metals used in these processes is not readily available. This paper provides the emissivity of a variety of metals used in wire-arc directed energy deposition processes. For the first time, the test samples were fabricated using typical deposition processes and systems. The metals evaluated were titanium alloy (Ti-6Al-4V), Inconel 718, mild steel, aluminum alloy 2319, and nickel aluminum bronze. At ambient temperature, the measured normal emissivity was 0.26–0.28 for Ti-6Al-4V; for Inconel 718, it was 0.45–0.54; for mild steel, it was 0.4–0.72; for aluminum 2319, it was 0.14; and for nickel aluminum bronze, it was 0.35. The approximate emissivity values are also given over the temperature range 20–1400 °C. The effect of residual oxygen in the shield gas on emissivity is explored for the first time. The spectrophotometric technique was used to measure the metal thermo-optical properties. Full article

To overcome the issues of excessive cutting force, poor chip segmentation, and premature tool wear during the drilling of Ti-6Al-4V titanium alloy. This study established the cutting edge motion trajectory function and instantaneous dynamic cutting thickness equation for ultrasonic vibration-assisted drilling through kinematic analysis. Based on this, an analytical model of drilling force was formulated, integrating tool geometry, cutting radius scale effects, dynamic chip thickness, and drilling depth. In parallel, a finite element model was constructed to achieve visual simulation analysis of chip deformation and cutting force. Finally, the accuracy of the model was verified through experiments, with a comprehensive analysis performed on how cutting parameters affect thrust force. The findings indicate that the average absolute prediction errors of thrust force and torque between the analytical model and finite element simulations were 7.87% and 6.26%, respectively, confirming the model’s capability to accurately capture instantaneous force and torque variations. Compared to traditional drilling methods, the application of ultrasonic vibration assistance resulted in reductions of 40.8% in thrust force and 41.7% in torque. The drilling force exhibited nonlinear growth as the spindle speed and feed rate were elevated, while it declined with greater vibration frequency and amplitude as drilling depth increased. Furthermore, the combined effect of optimized vibration parameters enhanced chip fragmentation, producing short discontinuous chips and effectively preventing entanglement. Overall, this research provides a theoretical and practical foundation for optimizing ultrasonic vibration-assisted drilling and improving precision hole making in titanium alloys. Full article

Titanium alloys are widely employed in structural and electrochemical applications owing to their excellent mechanical properties and inherent corrosion resistance. However, their stability in harsh acidic environments, such as those encountered in energy storage systems, remains a critical issue. In this study, composite ceramic coatings were synthesized on a Ti6Al4V alloy using plasma electrolytic oxidation (PEO) in silicate-, phosphate-, and sulfate-based electrolytes, with and without the addition of α-alumina nanoparticles. The resulting coatings were comprehensively characterized to assess their surface morphology, chemical and phase compositions, and corrosion performance. Thus, the corrosion current density decreased from 9.7 × 10⁴ for bare Ti6Al4V to 143 nA/cm² for the coating fabricated in phosphate electrolyte with alumina nanoparticles, while the corrosion potential shifted anodically from –0.68 to +0.49 V vs. silver chloride electrode in 5 M H₂SO₄. Among the tested electrolytes, coatings produced in the phosphate-based electrolyte with Al₂O₃ showed the highest polarization resistance (113 kΩ·cm²), outperforming those fabricated in silicate- (71.6 kΩ·cm²) and sulfate-based (89.0 kΩ·cm²) systems. The composite coatings exhibited a multiphase structure with reduced surface porosity and the incorporation of crystalline oxide phases. Notably, titania–alumina nanoparticle composites demonstrated significantly enhanced corrosion resistance. These findings confirm that PEO-derived composite coatings provide an effective surface engineering strategy for enhancing the stability of the Ti6Al4V alloy in aggressive acidic environments relevant to advanced electrochemical systems. Full article

This study explores the differences in oxidation color, oxidation products, and high-temperature oxidation resistance between TA1 and Ti-6Al-4V (TC4) titanium alloys following a 50 h oxidation treatment at 450 °C and 750 °C. A combination of analytical techniques—optical microscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and micro-Vickers hardness testing—was employed to characterize the morphology of the oxide layers, elemental distribution, phase composition, and microhardness variations. The results reveal that at 450 °C, both alloys develop relatively compact oxide films. TA1 exhibits a yellow–gray coloration, while TC4 displays a characteristic blue–violet interwoven color. At 750 °C, however, the oxide layers become porous and prone to spallation, with a brown appearance and predominance of TiO₂. XPS analysis confirms that Ti⁴⁺ (TiO₂) is the dominant oxidation state on both alloy surfaces at 750 °C, with TC4 showing a significantly higher content of Al₂O₃. Microhardness measurements indicate that high-temperature oxidation increases the hardness of both alloys, with TC4 consistently exhibiting higher hardness than TA1. TC4 demonstrates superior oxidation resistance: at 450 °C, it forms a denser oxide layer with lower oxygen uptake, while at 750 °C, its oxide layer thickens more significantly, likely due to increased brittleness and spallation. This study underscores the profound impact of high-temperature oxidation on the microstructure and mechanical properties of titanium alloys and highlights the critical role of oxide layer density and stability in determining oxidation resistance. These findings provide valuable insights for the application of TA1 and Ti-6Al-4V alloys in high-temperature environments. Full article

Microtextured cutting tools are widely used because of their excellent performance in cutting difficult-to-machine materials. The cutting performance of cutting tools largely depends on the size parameters of the microtextures used. This study focuses on the machining of titanium alloy Ti-6Al4 V using microgrooved cutting tools under dry-cutting conditions. Special emphasis is placed on exploring cutting performance under specific combinations of microgroove parameters. To determine the optimal parameter combination for cutting, the effects of different microgroove parameters (including the diameter, depth, spacing, and spacing between grooves and cutting edges) on cutting force, tool wear, and chip morphology were investigated. In this study, femtosecond laser technology was used to prepare microgroove-textured cutting tools with different parameters, and the cutting performance of these tools was analyzed. The results show that, when the groove diameter is 80 μm, the depth is 60 μm, the spacing is 80 μm, and the distance between the groove and the tool tip is 120 μm, the cutting performance of the tool is optimal: the cutting force is reduced by 13.9%, the degree of tool wear is minimized, and the degree of chip curling is more uniform. The research results can be applied to the actual processing of Ti-6Al4 V, which can help tool design, selection, and microtexture parameter optimization. Full article

Carbon fibre reinforced polymer (CFRP) is a composite material known for its light weight and exceptional durability, composed of carbon fibres within a polymer matrix. Despite its high cost, CFRP is favoured for its outstanding strength-to-weight ratio and rigidity. It is widely used in the aerospace industry and ship superstructures, among others. These components often rub against different materials in various structural and mechanical assemblies. These interactions typically occur where metallic fasteners, bearings, hinges, and sliding components interface with CFRP parts causing, for example, fretting wear. The main novelty of the present study consists of a systematic comparison of titanium (Ti6Al4V) and aluminium (AA2024-T6) alloy spheres under identical test conditions, evaluating how each material interacts with different CFRP configurations. CFRP was tested against titanium and aluminium alloy spheres as counterbodies under reciprocating sliding conditions. Different contact conditions (applied loads) were used for tribotests. The wear volume and coefficient of friction were determined, as well as the wear mechanisms. Different analytical techniques were employed, such as profilometry, optical microscopy (OM), and scanning electron microscopy (SEM/EDS), to characterise the wear tracks. It was possible to determine the coefficient of friction as well as the wear rate on both CFRP specimens and their respective counterbodies. It was found that the coefficient of friction (CoF) depends on load, fibre orientation, and counterbody material, ranging from 0.14 to 0.29. The lowest wear rate coefficient was observed for CFRP sliding against titanium alloy in the layer configuration, at 1.48 × 10⁻¹³ mm³/N·m. In contrast, aluminium alloy counterbodies experienced significantly higher wear, with a maximum wear rate of 6.88 × 10⁻⁵ mm³/N·m. Wear volume increased with load across all conditions and was highest for the CFRP cross-section against aluminium alloy. Full article

In this study, the properties of electrophoretically deposited (EPD) coatings on orthodontic implants made from Ti-6Al-4V alloy were evaluated during simulated implantation trials on animal bones. Three types of chitosan-based coatings were prepared using EPD: titanium nitride microparticles (TiNPs), titanium nitride nanoparticles (TiNNPs), and boron nitride particles (BNPs). Each of these coatings was also modified by adding a polylactic acid (PLA) layer using a dip-coating technique to compare their properties with and without this additional layer. The coatings were analysed using optical microscopy, confocal microscopy, and scanning electron microscopy (SEM) with elemental analysis. Surface roughness measurements of the coated implants were also conducted to highlight differences that could significantly influence the type and strength of the bone-implant interface, directly affecting the stability of the implant as an anchorage unit. Eventually, to evaluate the antibacterial properties of the EPD coatings, their antibacterial activity against both Gram-positive and Gram-negative bacteria strains was tested. Scanning electron observations confirmed the homogenous distribution of micro- and nanoparticles in all coatings. The highest surface roughness values were observed in layers containing titanium nitride nanoparticles (TiNNPs) and chitosan. The presence of an additional dip-coating PLA layer improved the adhesion, and its effect on the surface roughness depended on the particle size. While the antibacterial properties of the coatings show promising results, achieving optimal adhesion of the coatings to implants remains a challenge that requires further development. Full article

During machining, most of the mechanical energy is converted into heat. A substantial part of this heat is transferred to the cutting tool, causing a rapid rise in tool temperature. Excessive thermal loads accelerate tool wear and lead to displacement of the tool center point, reducing machining accuracy and workpiece quality. This challenge is particularly pronounced when machining titanium alloys. Due to their low thermal conductivity, titanium alloys impose significantly higher thermal loads on the cutting tool compared to conventional carbon steels, making the process more difficult. To reduce temperatures in the cutting zone, cutting fluids are widely employed in titanium machining. They have been shown to significantly extend tool life. Cutting fluids are broadly categorized into cutting oils and water-based cutting fluids. Owing to their distinct thermophysical properties, these fluids exhibit notably different cooling and lubrication performance. However, current research lacks comprehensive cross-comparative studies of different cutting fluid types, which hinders the selection of optimal cutting fluids for process optimization. This study examines the influence of three cutting fluids—emulsion, cutting oil, and synthetic oil-free fluid—on tool wear, temperature, surface quality, and energy consumption during flood-cooled end milling of Ti-6Al-4V. A novel experimental setup incorporating embedded thermocouples enabled real-time temperature measurement near the cutting edge. Tool wear, torque, and surface roughness were recorded over defined feed lengths. Among the tested fluids, emulsion achieved the best balance of cooling and lubrication, resulting in the longest tool life with a feed travel path of 12.21 m. This corresponds to an increase of approximately 200% compared to cutting oil and oil-free fluid. Cutting oil offered superior lubrication but limited cooling capacity, resulting in localized thermal damage and edge chipping. Water-based cutting fluids reduced tool temperatures by over 300 °C compared to dry cutting but, in some cases, increased notch wear due to higher mechanical stress at the entry point. Power consumption analysis revealed that the cutting fluid supply system accounted for 60–70% of total energy use, particularly with high-viscosity fluids like cutting oil. Complementary thermal and CFD simulations were used to quantify heat partitioning and convective cooling efficiency. The results showed that water-based fluids achieved heat transfer coefficients up to 175 kW/m²·K, more than ten times higher than those of cutting oil. These findings emphasize the importance of selecting suitable cutting fluids and optimizing their supply to enhance tool performance and energy efficiency in Ti-6Al-4V machining. Full article

The aim of this study was to analyze the effect of finishing methods on the surface quality of Ti-6Al-4V titanium alloy additively manufactured by selective laser melting. It was observed that among the finishing methods, water jet treatment did not produce significant changes, while the abrasive water jet proved effective in removing defects and smoothing the surface, especially at a pressure of 30 MPa. However, the risk of abrasive particle entrapment in the material was observed. Promising results were also obtained using the water–ice jet, which combines effective material removal with surface smoothing. The selection of the finishing method should be tailored to the application requirements. Further research will focus on optimization and the combination of techniques to improve the functional properties of titanium components. Full article

This research investigates the multi-objective optimization of micro-milling processes for the titanium alloy Ti-3Al-2.5V (grade 9) through the application of grey relational analysis. The incorporation of nanometer-sized particles in hybrid machining lubricants plays a crucial role in improving heat transfer during machining. The approach aims to increase the efficiency and effectiveness of micro-milling by addressing various performance metrics simultaneously, leading to better machining results for this titanium alloy. Additionally, the integration of nanoparticles into the machining lubricant significantly improves the lubrication properties, reducing friction during the machining process. The study analyzed four machining parameters: machining speed, rate of feed, axial depth of cut, and the weight percentage concentration of hybrid machining lubricants Multi-wall Carbon Nano Tube and Alumina Oxide (MWCNT and Al₂O₃). The machining nanolubricant was formulated by adding 1% and 2% volume concentrations of MWCNT and Al₂O₃ nanoparticles to the industrial machining fluid. In this machining context, the friction between the machining tool and the Ti-3Al-2.5V work piece is a vital factor influencing the output quality. The results demonstrate that the chosen machining parameters and machining lubricants have a direct impact on the coefficient of friction and surface roughness. The study concludes that utilizing machining nanolubrication for machining Ti-3Al-2.5V (grade 9) significantly enhances the quality compared with traditional machining lubricants. Full article

Background/Objectives: To prevent potential complications for patients with metal hypersensitivity requiring total knee arthroplasty (TKA), implant coatings have been developed. Thermal nitriding of the titanium surface creates a TiN layer that increases hardness and wear resistance while preventing release of cobalt and chromium ions. The aim of this study was to evaluate the clinical safety and performance of an anatomic implant system comprised of thermally nitrided Ti-6Al-4V. Methods: This is an ongoing prospective, multicenter observational cohort study of primary and revision TKA patients. Patient-reported outcome measures including the Oxford Knee Score (OKS), Knee Society Score (KSS) Expectations subscale, EQ-5D-5L, physical exams, and radiographic assessments to document abnormalities were investigated in 94 patients who provided at least two years of follow-up data. The primary endpoint was improvement in the Oxford Knee Score (OKS), defined as the minimal clinically important difference (MCID, 7.0 points). Results: All outcome measures including patient-reported function (OKS) demonstrated significant improvements (19.4–22.6 points) exceeding the MCID with no between-group differences by bearing types utilized. Health-related quality of life as measured by EQ-5D-5L improved over the cohort and was maintained at 2-years post-operative. In total, three (1.4%) radiographic abnormalities were observed, all of which resolved at two-year follow-up. 12 (5.3%) serious complications were reported, none of which were related to the device. Two revisions have occurred, one due to infection and one due to a fall, in the ultracongruent bearing cohort (survivorship 98.1%, 95%CI 87.4–99.7). Implant survivorship was 100% in all other bearing cohorts. Conclusions: This anatomically designed, thermally nitrided titanium alloy implant demonstrated clinically significant improvements in function, PROMs, and quality of life in patients undergoing TKA regardless of bearing type. Excellent two-year implant survivorship between 98.1% and 100% across cohorts were observed, with no radiographic abnormalities at 2 years. Full article

The objective of this study was to investigate the physicochemical properties of hybrid coatings with titanium nitride and boron nitride nanoparticles deposited on the TiAlV medical alloy via the sol–gel process. The developed layers were intended to impart bactericidal properties and provide protection against surgical abrasions during the implantation procedure. This study focused on evaluating the microstructure (SEM + EDS), structure (XRD, FTIR), and surface properties, including wettability, surface free energy, and roughness of the synthesized layers. Our results confirmed that it was feasible to produce hybrid layers with various microstructures and diverse layer morphologies. The FTIR and XRD structural analyses confirmed the presence of an organosilicon matrix incorporating the two aforementioned types of ceramic particles. Full article