Papers by Keyword: Titanium

Abstract: The paper considers approaches that can lead to the growth of micro-and nanocrystals on the surface of coatings formed on valve metals by plasma electrolytic oxidation (PEO). Among these approaches, there are the use of electrolytes-suspensions, the addition of organic compounds to the electrolytes, the thermal annealing of ‘PEO layer/metal’ composites, including impregnated ones.

Abstract: The paper presents results of investigation of biocompatible coatings on VT1-0 commercially pure titanium formed using plasma electrolytic oxidation (PEO) method. The effects of samples with different surface treatment on the functional activity of cells innate immunity have been studied. The study of enzymes has showed the higher stimulation of cellular metabolism during the first hour of contact with the PEO-coating in comparison with the uncoated titanium. The smallest immunostimulatory influence has been obtained for PEO-coating. It has been established that PEO-layers on titanium affect the functional state of cellular processes accompanying bone mineralization.

Abstract: 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.

Abstract: The machining of difficult-to-cut materials such as titanium plays a key role in several industries such as aerospace or medical. Approaches to overcome many difficulties when machining these materials can be an appropriate coating system for cemented carbide cutting tools. However, the atmosphere under which machining takes place, influencing the chemical tool wear, has not been taken into consideration. This work examines the tribochemical wear resistance of TiN, TiAlN and CrAlN coated carbide tools under different atmospheric conditions when cutting Ti6Al-4V. Air, technically pure argon and silane-doped argon is used to determine the influence of different oxygen levels on the wear behaviour of the tools. It has been found that oxidation of tools and tool coatings plays a significant role in tool wear when dry cutting titanium. Best results were generated using CrAlN and uncoated inserts where an increase in tool life up 50 % can be achieved when cutting in oxygen levels corresponding to extreme high vacuum (XHV) adequate atmospheres by using silane-doped argon. The benefits of XHV adequate atmospheres also have an effect on TiAlN-and TiN based coatings, but the chemical interaction of Ti element in the coating with the workpiece material, which presumably reduces wear resistance of cutting tools, cannot be outweighted or equalised by applying oxygen free atmospheres.

Abstract: The condenser in Steam Power Plant is critical equipment to convert steam from the steam output of the low-pressure turbine to become liquid. Thus, maintaining the reliability of the condenser will prevent progressive failure to other equipment. One of the methods to investigate their reliability is using eddy current test on the pure titanium grade 2 condenser tubes to measure their wall thinning level in comparison to their original thickness of 0.5 mm. Based on the measurement, any tubes having 0.05 mm in thickness (wall thinning level of 90%) and below are plugged to prevent potential leakage. In 2018, the condenser in unit 2 of Labuan steam power plant in Banten province, Indonesia was tested by eddy current on all tubes. Results indicate that condenser tube with wall tube thinning ≥ 90% were totaling 733 tubes (± 5% of the total tubes). The location and distribution of the highest probability of tubes leaking due to wall thinning problems were generated after statistical analysis. The data obtained in this unit can be used as a reference for maintenance strategy on other units working in the same condition. In order to understand the tube thinning mechanism, one tube at A-side inlet that has 97% of wall thinning level was cut and submitted to metallography and hardness testing. The results point out that no crack or corrosion product was found and the microstructure of the tubes did not alter as compared to their original tubes. This indicates that pure erosion mechanism takes place causing the thinning of the tubes.

Abstract: The main difficulty in obtaining adapters from stainless steel + zirconium metal combination lies in the formation of fragile intermetallic compounds at the weld border. By its properties, zirconium is very close to titanium, and therefore the manufacture of tubes from this combination, as well as pure titanium, is considerably difficult. Optimum explosion welding parameters have been developed, ensuring the highest adhesion strength compared to the existing production methods. At the weld border, a structure characteristic of compounds of dissimilar metals was revealed. The permissible heating temperatures for this combination are determined. The fundamental possibility of using the explosion energy as a factor stimulating the connection of dissimilar metals in order to obtain high-quality multilayer tubes, billets and products for various purposes is demonstrated, resulting in the introduction of environmentally friendly technology. Economic analysis of the manufacturing technology of bimetallic tubes by welding explosion was carried out. The cost-effectiveness of manufacturing technology of bimetallic stainless steel + zirconium metal compound nozzles, which is based on the use of high-pressure gradients and loading velocities to create production, was evaluated.

Abstract: Underwater laser machining process is a material removal technique that can minimize thermal damage and offer a higher machining rate than the laser ablation in ambient air. This study applied the underwater method associated with a nanosecond pulse laser for turning a commercially pure titanium rod. The effects of laser power, surface speed and number of laser passes on machined depth and surface roughness were investigated in this work. The results revealed that a deeper cut depth and smoother machined surface than those obtained from the laser ablation in ambient air were achievable when the underwater laser turning process was applied. The machined depth and surface roughness were found to significantly increase with the laser power and number of laser passes. The findings of this study can disclose the insight as well as potential of the underwater laser turning process for titanium and other similar metals.

Abstract: The metastable β Ti-6Al-4V alloy has been used clinically as a permanent implant material owing to its suitable mechanical properties and biocompatibility. However, the alloying element V was accused of causing toxicity when released to human body fluid. In this work, Nb was used in the alloy to replace V. This study presents the characterization of microstructure and mechanical hardness of as-cast Ti-6Al-7Nb and after solution treatment. The Ti-6Al-7Nb alloy was fabricated by the centrifugal casting method. Solution treatment was carried out at 970°C for 1 hour, followed by oil quenching, and consecutively an aging treatment was applied at 500°C for 8 hours. The microstructure was studied by an optical microscope. The mechanical hardness was measured by microhardness Vickers. The results show that the mechanical hardness of the Ti-6Al-7Nb decreased from 396.2 to 377.2 HV as a result of the solution treatment. Reduction in the hardness was attributed to the phase transformation of α to the β phase during the solution treatment. The XRD analysis showed a reduction in the intensity of α phases at the (011), (012), and (020) planes in the alloy after the solution treatment. The results indicated that the microstructure and mechanical hardness of Ti-6Al7-Nb alloy were affected by the solution treatment.

Abstract: Hydroxyapatite (HA) coating was deposited on commercially pure Ti to improve its biocompatibility as a biomedical implant material. The HA layer was deposited by the electrophoretic deposition (EPD) method. The processing parameters controlled the HA structure. In this research, the applied voltage was varied 20, 30, and 40 V to optimize a free-crack layer. The current output during EPD at 20 V was in the order of 10^-5 A/cm². A higher current density in the order of 10^-4 A/cm² was obtained at 30 and 40 V. The coating formed at 20 V was relatively free of crack. A high number of cracks began to observe in the layer formed at 30 V, while only a few cracks were revealed on the layer formed at 40 V. The average thickness of the HA layer increased slightly with applied voltage. The thickness was approximately 40±5 µm, as observed by an optical microscope. The optimum voltage to produce a thick HA layer with a small number of cracks was at 40 V.

Abstract: Ti-based coating has been used for biomaterials to improve biocompatibility, mechanical and corrosion properties. Each coating shows unique performance depending on a variety of factors such as coating microstructure and properties as well as in-service conditions. In this study, the microstructure, surface topography, hardness, adhesion and corrosion properties of Ti and TiN films on stainless steel 316L coated by cathodic arc physical vapor deposition process (PVD) were studied. The results showed that the surface roughness of 316L increased after being coated with Ti and TiN film as evidenced by the numerous particles and voids observed on the surface of both films. The hardness of 316L coated with Ti and TiN was increased by approximately 50% and 85%, respectively. Ti and TiN coated samples showed good adhesion strength with the first critical load (LC1) of approximately 10N and 15N, respectively. However, the types of film failure for Ti and TiN were found to be different. Partial delamination with a high degree of plastic deformation was observed for Ti coating, whereas surface cracks were found for TiN coating. This finding is likely attributable to the difference in flow resistance and the amount of particles and voids observed. All samples showed a stable passive region during 7 days of immersion in Ringer’s solution. Ti film showed better corrosion resistance than TiN, which may have been caused by the effect of more voids on TiN surfaces formed by PVD coating.