Solid State Phenomena Vol. 183

Abstract: Titanium and its alloys are common in medical implant applications because of their desirable properties, such as relatively low Young’s modulus, good fatigue strength, corrosion resistance, biocompatibility as well as formability and machinability. However, these materials cannot meet all of the clinical requirements. Current research focuses on improving not only the mechanical performance but mostly the biocompatibility of Ti-based systems through variations in alloy composition and surface treatment. One of the methods that allows the change of biological properties of Ti surface is the modification of its chemical composition. In this work plasma surface modification approach was used to improve mechanical properties by synthesis of composite layer structure on a pure titanium surface. The study aims at development of TiB precipitation dispersed uniformly at α-Ti matrix by plasma melting of Ti-2 wt% and Ti-10 wt% B alloy powders composition. Grain size of precursor powders obtained by mechanical alloying method and its homogenization can control the porosity and boron agglomeration tendency of the synthesized layers. Plasma procedure was taken under argon and helium inert atmosphere and surface was obtained by single passage of plasma pillar upon the prepared surface. The Vickers microhardness of obtained surface reached nearly 850HV, which was much higher compared with initial sample of the pure titanium substrate of 160HV. The surface corrosion resistance in 0.9% NaCl solution was nearly the same as for pure titanium, showing stable behaviour of created oxide layer, with no negative effect of dual phase microstructure. In vitro biocompatibility test in static condition was performed. All samples showed good cell growth. Our studies suggests that chemical composition of modified titanium surface by TiB precipitation by plasma alloying process has no negative effect on cytocompatibility.

Abstract: This paper presents results of oxidation tests and corrosion investigations of titanium alloy Ti13Nb13Zr performed at different conditions. The oxide layers have been formed by electrochemical method in 2M H₃PO₄ + 0.3% HF solution for 30 min. and 1 h at 20 V constant voltage. The corrosion tests have been made by potentiodynamic method in Ringer`s solution at pH ranged between 3 and 7. It has been shown that the nanooxide films, which improve corrosion resistance of titanium alloy Ti13Nb13Zr even if acidic environment, have appeared.

Abstract: The aim of the work was evaluation of electrochemical properties of Co-based alloys (Remanium GM 800+ and Biosil F) and Ni-based alloys (Heraenium NA and Remanium G-Soft) commonly used on frameworks for porcelain faced cast partial dentures. First stage of the work was evaluation of surface roughness by means of direct linear contact measurement (SURTRONIC 3+ profiler, Taylor/Hobson) of samples after casting and surface treatment. Electrochemical properties of surface were assessed by means of potentiodynamic and impedance methods. In potentiodynamic tests, in order to evaluate pitting corrosion resistance of the analyzed alloys, anodic polarization curves were recorded. The VoltaLab® PGP 201 system was applied in corrosion tests. Moreover, in order to evaluate structure and properties of the surface layer the electrochemical impedance spectroscopy (EIS) was applied. Selection of this method enabled to determine the impedance of the material – surface layer – solution interface with the use of approximation of impedance data by means of equivalent electric circuit model. The EIS tests were carried out with the use of the AutoLab PGSTAT 302N system equipped with the FRA2 Faraday impedance module. Electrochemical tests were carried out in artificial saliva at the temperature of 37°C and pH = 7,0±0,1.

Abstract: Aluminium alloys are the materials of choice when high-strenght-to-weight rations are required in structural components, and used widely in the automotive and aerospace industries. As an example, the use of an aluminium components in the automobile industry has greatly increased due to weight savings and resultant fuel economy improvements. There are many methods of surface consolidation of an aluminium alloys. This work presents the hybrid creation method of the newly layers type (Mn-P) on the AlSi13Mg1CuNi alloy, its microstructure, hardness, chemical and phase compositions as well as wear and corrosion resistance. Growth the wear resistance of an aluminium alloy coated with the layer type (Mn-P) is visable. The corrosion characteristics of these layers are also considered.

Abstract: Research on improvement of structure and fabrication methods of the bone implants are carried out for many years. Research are aimed to shape the structures, that will have a Young's modulus value similar to the value of the human bones Young's modulus. Depending on the porosity, Young’s moduli can even be tailored to match the modulus of bone closer than solid metals can, thus reducing the problems associated with stress shielding of a human bones. The designed structure should also be characterized by a high abrasion and corrosion resistance to and allow bone ingrowth in the implant material to make the best bone-implant fixation. For this purpose, implants should have a porous structure with an appropriate pore size and with open-cell porosity. Material for bone implants must also have a high biocompatibility and bioactivity. Following these requirements, the metallic porous materials appear to be the most suitable material for bone implants. In this paper a various methods of a porous materials fabrication for bone implants are listed. It was shown that titanium and its alloys (e.g. Ti6Al4V or Ti13Nb13Zr) are widely used as biomaterials for implants. Research in order to increase their wear and corrosion resistance and to improve their biocompatibility and bioactivity are still carried out. One of the most effective methods of manufacturing the porous materials is a powder metallurgy (PM). In this paper the results of research under shaping the structure of the porous titanium alloy Ti13Nb13Zr are also presented. As a manufacturing method of the porous material from the investigated and mentioned above Ti alloy, the powder metallurgy (PM) was choosen - with and without the use of a space holders. Method of fabrication a spherical powder from the aforementioned Ti alloy and results of its morphology research are discussed. The applied powder compaction method (with use and without use of space holders) and the influence of a sintering process on the final microstructure morphology of porous material obtained from Ti13Nb13Zr alloy are also presented and discussed.

Abstract: In the paper the experimental results of the dynamic tests of the MRE samples cured without and under magnetic field are presented and compared. The samples (55 mm diameter and 70 mm) were made of the polyurethane elastomer PU 70/30 with the admixture of the ferromagnetic particles (in this case – carbonyl iron spheres with the diameter of about 9 μm). The samples with ferromagnetic particles were cured without as well as under the external, parallel to the vertical axis of the sample, magnetic field of the 300 mT intensity. The experiments were carried out on the materials testing machine for static and dynamic loads INSTRON 8802. The machine was additionally equipped with the measurement head of 4kN scope and the magnetic coil that produces the magnetic field of the intensity up to 500 mT. Cycled load was applied to the MRE samples. In the case of the dynamic tests the sinusoid cyclic variable load was used. The applied load frequency was 1 Hz in each presented test. The samples were cyclically compressed of the 10, 15, 20 and 25 % of their height. On the base of the obtained results the force maximum values and the dumping coefficient (the energy dissipation coefficient) in each dynamic tests were calculated. The hysteresis loops in the load – displacement charts that were observed during the cyclic tests. The influence of the internal structure of the researched material on its strength behaviour is taken into consideration.

Abstract: The influence of oxidation time on the microstructure and mechanical property, especially on the hardness, and of Co-base alloy coatings were investigated. Coatings were manufactured by PTA cladding. The cobalt alloy was exposed to temperature 800°C in air for 1, 22 and 200 hours. As a result of oxidation treatment the scale layers were formed and changes in microstructure was observed. Also changes in hardness were noticed.

Abstract: The geometry of self-organized TiO₂ nanotubes, obtained by electrochemical anodization, has been determined by using fuzzy reasoning approach. The efficiency of TiO₂ nanotubular layer in biomedical applications depends on geometry and available surface area of nanotubes, which can be determined by their diameter and length. The structure of nanotubes depends on processing parameters of electrochemical anodization, like applied potential, anodization time, and pH of electrolyte. A proposed method showed the possibility of estimation and optimization the nanotubular architecture on Ti and Ti alloys by choosing the appropriate processing parameters based on representative experimental data. A fuzzy reasoning approach was utilized by using Matlab Software.

Abstract: Positive nature of the effects of hydrogen on the properties of titanium alloys is manifested in the high temperature hydrogen treatment (HTM - Hydrogen Treatment of Materials), where hydrogen is temporary alloying component. This is possible because of the high values ​​of diffusion coefficients can be easily introduced into the titanium and it just as easily removed. Titanium and its alloys exhibit a high affinity for hydrogen absorption capacity, about 60% at. hydrogen at 600 °C. The hydrogen in titanium alloy is present in the form – an interstitial solution or titanium hydride. Since the specific volume of titanium hydride is about 13 ÷ 17% higher compared to α phase, it is high stress in the crystal lattice of this phase leads to local plastic deformation and large deformation phase. The paper presents the results of the possibilities of hydrogen using as a temporary alloying element in Ti-6Al-4V alloy. Treatment of hydrogen alloy consisted of three stages: hydrogenation in hydrogen gas atmosphere at 650 °C, a cyclic hydrogen-treatment (3 cycles 650 °C or 950 °C to 250 °C) and a dehydrogenation in vacuum (550 °C). It was shown that hydrogen affects appreciably changes the microstructure of surface layer of the tested titanium alloy. The aim of this study is thus to determine the effect of hydrogen on the two-phase microstructure, hardness, and corrosion resistance of the titanium alloy Ti-6Al-4V due to high-temperature hydrogen treatment.

Abstract: In the paper researches results of corrosion properties of Ni-Al alloy and Ni-Al-Al₂O₃ composite coatings were presented. Coatings were obtained by flame spraying of "Casto-Dyn 8000" torch. During coatings flame spraying of torch was used a small distance from the substrate. Instead of commonly used spray distance 150 mm, 100 mm was used. The studies in 0.01 M H₂SO₄ and 3.5% NaCl (artificial seawater) environments were realized. Evaluated coatings are more corrosion resistant in the 3.5% NaCl environment than in the 0.01 M H₂SO₄. Corrosion current density for alloy coatings in artificial seawater was 20 μA/cm² and 223 μA/cm² in an acidic environment. The value of corrosion potential in an environment of 3.5% NaCl is about 200 mV lower than in 0.01 M H₂SO₄. Composite coatings Ni-Al-Al₂O₃ were characterized by a lower corrosion current densities and increased resistance than Ni-Al coatings in acidic environment. The presence of alumina in the coating matrix caused increased corrosion current density in sea water environment.