Cast Titanium Research Articles

Discrepancy of complete-arch titanium frameworks manufactured using selective laser melting and electron beam melting additive manufacturing technologies

Statement of problemTitanium frameworks for implant-supported prostheses can be additively manufactured using different powder-based fusion technologies, including selective laser melting (SLM) and electron beam melting (EBM). Some manufacturers have developed a technique that combines the printing of the framework with the subsequent machining of the implant interface. Whether these technologies produce frameworks with acceptable accuracies is unclear. PurposeThe purpose of this in vitro study was to evaluate the discrepancy obtained from the digitizing procedures of the definitive cast, the implant-prosthesis discrepancy, and the distortion of the manufacturing processes in the fabrication of titanium frameworks for implant-supported complete-arch prostheses manufactured using SLM and EBM additive manufacturing technologies. Material and methodsA completely edentulous mandibular definitive cast with 4 implant analogs and a replica of a screw-retained interim restoration was obtained. A standard tessellation language (STL) file of the framework design was prepared using dental software (Exocad). Six frameworks were manufactured using either SLM (3D Systems) or EBM (Arcam) technologies. Discrepancy (μm) was measured at the x- (mesiodistal), y- (buccolingual), and z- (occlusogingival) axes by using the formula 3D=x2+y2+z2 three times by best-fit superimposure of the definitive cast STL file, the definitive cast titanium framework, and the framework STL file by using a coordinate measuring machine (CMM) controlled by software (Geomagic). The Kruskal-Wallis and Mann–Whitney U statistical tests were used (α=.05). ResultsThe digitizing procedures of the definitive cast showed a mean accuracy of 3 ±3 μm. Except for the z-axis (P<.05), no significant differences were observed between the SLM and EBM technologies for implant prosthesis discrepancy for the x- or y-axis (P>.05). The most favorable results were obtained in the z-axis, representing the occlusogingival direction. Three-dimensional discrepancy measurements in all comparisons ranged between (60 ±18 μm and 69 ±30 μm) and were not statistically significant (P>.05). The highest discrepancy was observed in the y-axis (37 to 56 μm), followed by the x- (16 to 44 μm) and z- (6 to 11 μm) axes (P<.05). ConclusionsThe titanium frameworks analyzed for a complete-arch implant-supported prosthesis fabricated using either the SLM or EBM additive technologies showed a clinically acceptable implant-prosthesis discrepancy, where similar discrepancies on the x-, y-, and z-axes were found between the additive manufacturing technologies. Both technologies showed comparable abilities to manufacture the STL file additively on the x-, y-, and z-axes.

Influence of electric arc treatment of inner surfaces of ceramic molds on the formation of the surface of titanium casting

Influence of the effect of electric arc titanium spraying on the inner surfaces of ceramic molds used for casting titanium was observed. Casting surface and cross-section were examined by electron microscopy with a probe microanalysis system and X-ray photoelectron spectroscopy. It was observed there is an “alpha case” on the casting surface. Its thickness and elemental composition varies through the casting surface.

Functional coatings for titanium casting molds using the replica technique

The quality of titanium cast parts depends not only on the corrosion reaction of the mold in contact with the titanium alloy melt, but also on the dimensional accuracy and the surface quality of the investment casting mold. Usually, the ceramic mold is produced by dip-coating. This contribution investigated the coating properties of green calcium zirconate (CaZrO3) coatings produced by the replica technique. Thus, the effect of different coating slurries as well as different coating technologies on important coating properties was analyzed. In all cases, centrifuging and spraying produced thinner coatings compared to dip-coating. Using an appropriate coating slip, particularly centrifuging revealed a cohesive homogeneous coating surface and is therefore a promising technology for the production of functional coatings for titanium casting molds.

Photoelastic analysis of the influence of prosthetic material on the stress distribution in bone around implant

Objective: To provide a reference for a suitable alternative treatment choice for implant-supported prostheses, and to explore the influence of 3 types of prosthetic material on the stress distribution around implant. Methods: The implant-abutment analogs were embedded individually into photoelastic resin blocks, which were medical pure titanium castings reproducing the surface and outline of implant (diameter 4.3 mm, length 11.5 mm) and esthetic abutment (regular profile, 1 mm). The prostheses were divided into 3 groups according to the type of prosthetic material. Each group consisted of 5 samples. The samples of composite resin ceramic and zirconia group were milled by chair-side computer aided design and computer aided manufacture (CAD/CAM) system. The samples of porcelain-fused-to-metal crown group were made manually and a pre-arranged silicone rubber impression of CAD/CAM crown would guide to shape the veneer porcelain. Each set was submitted to a 300 N compressive load axially or obliquely (75°). The stress value in the peri-implant bone at the level of the neck, neck1/3, middle1/3 and root1/3 of the sections (0.5, 1.5, 2.5, 3.5 mm) from implant was analyzed by digital photoelasticity, and the stress cushioning effect of 3 types of prosthetic material was comprehensively evaluated. Results: The time spent reaching the stress peak of composite resin ceramic group [(1.58±0.08) s, axially; (2.75±0.21) s, obliquely] was larger than that of the zirconia group [(1.40±0.12) s, axially; (2.30±0.25) s, obliquely] (P<0.05) under the same download mode. Although there were no significant differences in equivalent stress values of the measurement points among the three groups (P>0.05), a downward trend of equivalent stress values of composite resin ceramic group was observed compared to zirconia group, regardless of load type. When loaded obliquely, the highest degree of stress concentration at the level of the neck of implant were found in the porcelain-fused-to-metal crown group. Conclusions: Within the limitations of this study, composite resin ceramic was more beneficial to the biomechanical behavior of implant in stress buffer compared to zirconia.

Comparative study of commercially pure titanium produced by laser engineered net shaping, selective laser melting and casting processes

Commercially pure titanium was produced using laser engineered net shaping (LENS) and selective laser melting (SLM) processes. The SLM and LENS processing parameters as well as critical aspects including densification and balling effect were investigated. The resulting properties were studied and compared with those from traditional casting. Investigation of the processing parameters showed that significantly higher laser power and energy density is required in LENS compared to SLM in order to obtain near full density (99.5%). The microstructural investigations revealed an α microstructure with mixed morphologies including plate-like and widmanstätten for LENS somewhat similar to the serrated and fine acicular α obtained from casting. In contrast, the SLM samples showed only martensitic α′ phase mainly with a lath-type morphology. The difference between SLM and LENS microstructures was discussed based on interrelated aspects including energy density, solidification rate and specific point energy. Differences in their microstructures are mainly associated with differing rates of cooling and differing energy densities during SLM and LENS processing. Compression and hardness tests indicated that SLM titanium possesses better mechanical properties due to a fine grain size and martensitic phase composition, whereas LENS and cast titanium with α microstructures show similar mechanical properties.

Compositional and microstructural optimization and mechanical-property enhancement of cast Ti alloys based on Ti-6Al-4V alloy

The effects of alloying additions on the microstructure and mechanical properties of cast Ti alloys based on Ti-6Al-4V were systematically investigated through a combination of thermodynamic calculations and experimental verifications. New cast titanium alloys with significantly improved properties were developed through combining thermodynamic calculations and physical metallurgy principles, which achieve an optimum combination of high strength and high ductility at both room and elevated temperatures. Our analysis indicates that the improved strength is due mainly to the α colony and lath size refinement induced by both macro- and micro-alloying of Cr, Fe, B and C elements, whereas the mechanisms for such property optimization include: (1) an increased volume fraction of ductile β phase in the cast state, (2) a refined α colony and lath size by the Cr, Fe, B and C alloying additions, and (3) an enhanced grain-boundary cohesion and refined grain size of prior-β grains induced by proper amount of B additions. The newly developed cast Ti alloys with substantially enhanced mechanical properties for engineering applications.

Thermo hydrogen treatment for microstructure refinement and mechanical properties improvement of Ti-6Al-4V alloy

Cast titanium alloys are of great importance in industry, but their mechanical properties are under satisfaction and difficult to improve. Thermo hydrogen treatment (THT) offers a method for the microstructural refinement of titanium alloys without deformation, and thus attracts the attention of researchers. In this work, THT is performed on cast Ti-6Al-4V alloy, including hydrogenation, solution-aging treatment and dehydrogenation. The microstructure evolution during the THT process is carefully studied, and the role of each step for microstructure refinement is carefully evaluated, leading to the conclusion that the solution-aging treatment is the most important step for refinement. Tensile properties of the samples treated with THT were obtained, showing that the THT can increase the tensile strength of the as-cast alloy by ~ 27.44%.

Prediction of mechanical performance of Ti6Al4V cast alloy based on microCT-based load simulation

The effect of porosity on the mechanical properties of cast titanium alloy was investigated in this work, specifically for investment-cast Ti6Al4V. X-ray micro computed tomography (microCT) was used to non-destructively analyse pores in 10 samples prior to mechanical testing. A finite element analysis was done on the microCT data providing a 3D view and quantitative values for maximum stress areas. All 10 samples were again analysed by X-ray microCT after physical testing. This allowed the location of failure to be correlated to pores and regions of high stress from the calculations. All samples showed high tensile strength with little effect of the pore size or simulated stress, most likely due to the simplified casting geometry. Irrespective of the microstructure, it was found that an increasing pore size results in increasing simulated stresses around the pores, which correlate strongly with a decrease in the measured ductility of the samples. This result indicates that induced stresses when a sample is put under load affects the ductility, since ductility depends on stress state of the material. Moderate correlation of the simulated stresses with ultimate tensile strength was found for samples with homogeneous microstructure.

Fretting Corrosion Behavior of Experimental Ti-20Cr Compared to Titanium.

Experimental cast titanium alloys containing 20 mass% chromium (Ti-20Cr) show preferable mechanical properties and a good corrosion resistance. This study evaluated the fretting corrosion behavior of Ti-20Cr. Ti-20Cr (n = 4) and commercially pure titanium (CP-Ti, n = 6) disk specimens were used. The fretting corrosion test was performed by electrochemical corrosion at 0.3 V in 0.9% saline solution and mechanical damage using 10 scratching cycles with three different scratching speeds (10–40 mm/s) at 10 N. After testing, the activation peak, repassivation time and surface morphology of each specimen were analyzed. The differences between the results were tested by parametric tests (α = 0.05). The average activation peaks were significantly higher in CP-Ti than in Ti-20Cr (p < 0.01), except at 20 mm/s. In the series of scratching speeds, faster scratching speeds showed higher activation peaks. The maximum activation peaks were also higher in CP-Ti. Slight differences in the repassivation time were observed between the materials at every scratching speed; faster scratching speeds showed shorter repassivation times in both materials (p < 0.05). CP-Ti showed severe damage and significantly higher wear depth than Ti-20Cr (p < 0.05). In conclusion, adding chromium to titanium reduced surface damage and improved the fretting corrosion resistance.

Evaluation of Mechanical Properties and Marginal Fit of Crowns Fabricated Using Commercially Pure Titanium and FUS-Invest.

This study investigated the mechanical properties and single crown accuracy of the tailor-made Fourth University Stomatology investment (FUS-invest) for casting titanium. Background. Current investment for casting titanium is not optimal for obtaining high-quality castings, and the commercially available titanium investment is costly. Methods. Titanium specimens were cast using the tailor-made FUS-invest. The mechanical properties were tested using a universal testing machine. Fractured castings were characterized by energy-dispersive spectroscopy. 19 titanium crowns were produced using FUS-invest and another 19 by Symbion. The accuracy of crowns was evaluated. Results. The mechanical properties of the titanium cast by FUS-invest were elastic modulus 125.6 ± 8.8 GPa, yield strength 567.5 ± 11.1 MPa, tensile strength 671.2 ± 15.6 MPa, and elongation 4.6 ± 0.2%. For marginal fit, no significant difference (P > 0.05) was found at four marker points of each group. For internal fit, no significant difference (P > 0.05) was found between two groups, whereas significant difference (P < 0.01) was found at different mark point of each group. Conclusions. The mechanical properties of titanium casted using FUS-invest fulfilled the ISO 9693 criteria. The marginal and internal fit of the titanium crowns using either the FUS-invest or Symbion were similar.

Bonding durability between acrylic resin adhesives and titanium with surface preparations.

The purpose of the present study was to evaluate the efficacy of pretreatment on the bonding durability between titanium casting and two acrylic adhesives. Cast titanium disk specimens treated with four polymer-metal bonding systems as follow: 1) air-abraded with 50-70 μm alumina, 2) 1)+Alloy Primer, 3) 1)+M.L. Primer and 4) tribochemical silica/silane coating system (Rocatec System). The specimens were bonded with M bond or Super-bond C&B adhesive. The shear bond strengths were determined before and after thermocycling (20,000 cycles). The surface characteristics after polishing, and for the 1) and 4) preparations were determined. The bond strengths for all combinations significantly decreased after thermocycling. The combination of Super-bond C&B adhesive and 2) led to significantly higher bond strength than the other preparations after thermocycling. The maximum height of the profile parameters for the polishing group was lower than other preparations.

Effect of Hypoeutectic Boron Additions on the Grain Size and Mechanical Properties of Ti-6Al-4V Manufactured with Powder Bed Electron Beam Additive Manufacturing

In additive manufacturing, microstructural control is feasible via processing parameter alteration. However, the window for parameter variation for certain materials, such as Ti-6Al-4V, is limited, and alternative methods must be employed to customize microstructures. Grain refinement and homogenization in cast titanium alloys has been demonstrated through the addition of hypoeutectic concentrations of boron. This work explores the influence of 0.00 wt.%, 0.25 wt.%, 0.50 wt.%, and 1.0 wt.% boron additions on the microstructure and bulk mechanical properties of Ti-6Al-4V samples fabricated in an Arcam A2 electron beam melting (EBM) system with commercial processing parameters for Ti-6Al-4V. Analyses of EBM fabricated Ti-6Al-4V + B indicate that the addition of 0.25–1.0 wt.% boron progressively refines the grain structure, and it improves hardness and elastic modulus. Despite a reduction in size, the β grain structure remained columnar as a result of directional heat transfer during EBM fabrication.

Influence of the retentional lattice form on the dimensional accuracy of CP titanium cast plates

Influence of the retentional lattice form on the dimensional accuracy of CP titanium cast plates

Рушійна сила процесу наводнення металів. ІІ. Титан литий

Рушійна сила процесу наводнення металів. ІІ. Титан литий

Comparison of medical and industrial X-ray computed tomography for non-destructive testing

Industrial X-ray computed tomography (CT) is an emerging laboratory-based non-destructive testing technique used in a variety of applications for samples ranging from 1 mm to usually 300 mm in diameter. Usually, microCT scanners are used for industrial non-destructive testing due to the superior resolution possible compared to medical CT scanners, but it is not generally known that medical CT scanners can produce reasonable results when high resolution is not needed. As demonstrated in this case study of very dense objects, far shorter scan time is required, compared to conventional laboratory industrial CT systems, consequently being a better solution for applications such as quick scout-scans, high throughput applications and larger objects. This case study makes use of four typical industrial test objects, specifically chosen as candidates which would be expected to be too dense for relatively low-voltage medical scanners. The respective test objects were scanned with both medical and microCT scanners and the results compared for the purpose of industrial non-destructive analysis. The test objects are a steel turbine blade, a titanium casting, a concrete cylinder with aggregate stones and porosity, and a concrete block with metal fiber reinforcement.

Effect of plasma nitriding and titanium nitride coating on the corrosion resistance of titanium

Statement of problemThe passive film on the surface of titanium can be destroyed by immersion in a fluoridated acidic medium. Coating with titanium nitride (TiN) may improve the corrosion resistance of titanium. PurposeThe purpose of this in vitro study was to investigate the effect of duplex treatment with plasma nitriding and TiN coating on the corrosion resistance of cast titanium. Material and methodsCast titanium was treated with plasma nitriding and TiN coating. The corrosion resistance of the duplex-treated titanium in fluoride-containing artificial saliva was then investigated through electrochemical and immersion tests. The corroded surface was characterized by scanning electron microscopy (SEM) with energy-dispersive spectroscopy surface scan analysis. The data were analyzed using ANOVA (α=.05) ResultsDuplex treatment generated a dense and uniform TiN film with a thickness of 4.5 μm. Compared with untreated titanium, the duplex-treated titanium displayed higher corrosion potential (Ecorr) values (P<.001) and lower corrosion current density (Icorr) values (P<.001). SEM results showed that the surface of untreated titanium was more heavily corroded than that of duplex-treated titanium. Surface scan analysis of duplex-treated titanium that had been immersed in artificial saliva containing 2 g/L fluoride revealed fluorine on the titanium surface, whereas fluorine was not observed on the surface of untreated titanium after immersion in fluoride-containing artificial saliva. The concentration of titanium ions released from the treated titanium was less than the amount released from untreated titanium (P<.001). ConclusionsDuplex treatment by plasma nitriding and TiN coating significantly improved the corrosion resistance of cast titanium in a fluoride-containing environment.

Effect of Zr, Mo and TiC on microstructure and high-temperature tensile strength of cast titanium matrix composites

In this paper, five types of TiC particle reinforced titanium matrix composites (TiC-PTMCs) were fabricated by casting route in order to investigate the influence of Zr, Mo and TiC on microstructures and tensile strengths of TiC-PTMCs. The increase of Zr content promoted the precipitation of eutectic TiC and refined primary TiC, while increasing Mo content led to the refinement of α lath. The composites with high Zr and Mo contents and low TiC content showed superiority in ultimate tensile strength (UTS) below 650°C, whereas above 700°C, high UTS was obtained in the composites with high TiC content and low Mo content. Below 650°C, solid solution strengthening and fine grain strengthening of matrix make the largest contribution to the improvement of UTS. However, above 700°C, solid-solution strengthening of Zr and the load bearing effect of TiC play a dominant role in the enhancement of UTS. Accordingly, effective routes for improving UTSs of TiC-PTMCs in different temperature ranges are different.

A Titanium Cast Hollow Definitive Obturator Prosthesis for a Maxillectomy Patient

ABSTRACT Oral cancer necessitates the surgical removal of all or part of the maxilla. The extent of surgical resection is dependent on the size, location, and potential behavior of the tumor. The maxillectomy procedure leaves the patient with a defect that compromises of the integrity and function of the oral cavity, leading to hypernasal speech, fluid regurgitation into the nasal cavity, and impaired masticatory function. Rehabilitation of subtotal and total bilateral maxillectomy surgical defects is a complex challenge to the prosthodontist. Prosthetic rehabilitation of the surgical defect with the help of obturator is very important, because the resulting functional deficiencies have a detrimental effect on the quality of life and self-esteem of the patient. How to cite this article Fernandez T, Rodrigues SV, Vijayanand KR. A Titanium Cast Hollow Definitive Obturator Prosthesis for a Maxillectomy Patient. Int J Prosthodont Restor Dent 2016;6(3):69-72.

Rehabilitation of edentulous maxillary arch with implant-assisted fixed complete prosthesis using multi-unit straight and angulated abutments

In comparison to an edentate mandible, rehabilitation of a completely edentulous maxilla using osseointegrated implants has always tested the ability of clinician and laboratory technician. Complex anatomy, as well as the biomechanical limitations of the maxillary bone, resists the placement of implant in its ideal location. This article illustrates a two-stage surgical and prosthetic management of edentulous maxilla opposing natural teeth using seven implants. This case report highlights the advantages of multi-unit straight and angulated abutments, torqued onto the implants, over which a cast titanium framework was made for fabrication of implant-assisted fixed complete dental prosthesis (FP-3 prostheses).

Morphology evolution of α phase in investment cast titanium matrix composites with B4C additions

Titanium matrix composites were prepared by investment casting in a consumable arc skull casting furnace. With the addition of B4C, the average primary β grains are refined, and the morphology of α phase tends to be more equiaxed. The free energy for nucleation consisting of the bulk free energy, orientation-independent interfacial energy, and elastic strain energy is calculated to investigate the role of nucleation sites in determining the shape of critical nucleus. In the current study, the TiB whiskers were found to be arranged in the grain boundary and provide heterogeneous nucleation sites for α precipitates, and the interfacial energy is about 14 % more than that in Ti-64, while its elastic strain energy is reduced to about three quarters of the latter one.