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Cobalt–chromium alloys (Co-Cr) are widely used in dentistry due to their excellent mechanical properties and corrosion resistance. Since prosthetic materials must be permanently stable in the oral cavity, it is very important to determine the release of ions from alloys in the oral cavity. In dentistry today, metals and alloys are mainly joined by laser and tungsten inert gas (TIG) welding. Therefore, in this work, the release of metal ions from six different Co-Cr alloys joined by these two welding methods was quantified to determine the effects of the welding method on an ion release. Static immersion tests, atomic absorption spectrometry and statistical analysis were performed for this purpose. The results showed that laser-welded alloys release a lower amount of metal ions compared to TIG-welded alloys.

Due to their good mechanical and other properties, cobalt-chromium alloys (Co-Cr) are often used in prosthetic therapy. The metal structures of prosthetic works can be damaged and break, and depending on the extent of the damage, they can be re-joined. Tungsten inert gas welding (TIG) produces a high-quality weld with a composition very close to that of the base material. Therefore, in this work, six commercially available Co-Cr dental alloys were joined by TIG welding, and their mechanical properties were evaluated to determine the quality of the TIG process as a technology for joining metallic dental materials and the suitability of the Co-Cr alloys used for TIG welding. Microscopic observations were made for this purpose. Microhardness was measured using the Vickers method. The flexural strength was determined on a mechanical testing machine. The dynamic tests were carried out on a universal testing machine. The mechanical properties were determined for welded and non-welded specimens, and the results were statistically evaluated. The results show the correlation between the investigated mechanical properties and the process TIG. Indeed, characteristics of the welds have an effect on the measured properties. Considering all the results obtained, the TIG—welded I—BOND NF and Wisil M alloys showed the cleanest and most uniform weld and, accordingly, satisfactory mechanical properties, highlighting that they withstood the maximum number of cycles under dynamic load.

Titanium based alloys are increasingly used in biomedicine due to their favourable properties. However, because of their high cost, new methods are being developed to produce more economical alloys. Therefore, in the framework of this work, Ti-20Nb alloy was produced by powder metallurgy. Namely, experimental alloy was prepared by mechanical alloying in a ball mill. The samples were singled out from the powder mixture and pressed on a hydraulic press. Sintering was carried out in a tube furnace in an argon atmosphere. Different processing parameters regarding the time and temperature of sintering were applied. Chemical homogeneity was analysed using the energy-dispersive spectrometry. Porosity was observed using the light microscope and microhardness was determined by Vickers method. The obtained results show that with a small correction of the applied technological parameters, in terms of time extension of mixing/mechanical alloying, it is possible to produce economically Ti-20Nb alloy having the properties suitable for biomedical application by using powder metallurgy technology.

In this paper, thermomechanical processing of niobium microalloyed steel was performed with the purpose of determining the interaction between niobium precipitates and dislocations, as well as determining the influence of the temperature of final deformation on the degree of precipitation and dislocation density. Two variants of thermomechanical processing with different final rolling temperatures were carried out. Samples were studied using electrochemical isolation with an atomic absorption spectrometer, transmission electron microscopy, X-ray diffraction analysis, and universal tensile testing with a thermographic camera. The results show that the increase in the density of dislocations before the onset of intense precipitation is insignificant because the recrystallization process takes place simultaneously. It increases with the onset of strain-induced precipitation. In this paper, it is shown that niobium precipitates determine the density of dislocations. The appearance of L&uuml, ders bands was noticed as a consequence of the interaction between niobium precipitates and dislocations during the subsequent cold deformation. In both variants of the industrial process performed on the cold deformed strip, L&uuml, ders bands appeared.

This paper presents the results of testing the corrosion behaviour of K110 tool steel for cold work in industrial emulsion medium (Lenox Band- Ade semi-synthetic oil + water, in a ratio of 1:10), water and 3.5% NaCl medium. Using the method of electrochemical impedance spectroscopy (EIS) and Tafel extrapolation, electrochemical measurements were performed in order to determine the corrosion parameters. After polarization measurements, the surface of the sample was examined with an optical microscope. Tafel extrapolation of the polarization curves revealed that the tested tool steel showed the lowest corrosion rate in the Lenox Band-Ade emulsion medium and the highest in the medium of 3.5% NaCl. The obtained results were confirmed by the method of electrochemical impedance spectroscopy, where the lowest charge transfer resistance was registered in the 3.5% NaCl medium, which indicates the fact that the thinnest oxide layer was formed in tested medium, which has a very weak protective role in the corrosion process. Metallographic analysis of the sample surface after polarization measurements in 3.5% NaCl medium indicates the occurrence of pitting corrosion caused by the action of aggressive chloride ions from the solution, which caused the destruction an already weak passive layer on the metal surface. At the same time, chloride ions from the acid medium attack more aggressively the matrix of the metal base of the tool steel, in contrast to the precipitated carbides on the sample surface.

Precision cold-drawn tubes are produced by cold drawing and cold pilgering. The cold drawing of the tubes is carried out at the so called draw bench, where the diameter of the tube from a larger diameter to the smaller is drawn through the die of certain dimensions. In order to obtain the required thickness of the tube wall and diameter, it is necessary to carry out the annealing before the next draw. This paper presents the results of cold drawn tubes. Research was carried out on steel E355. The tube diameter of 30 mm and wall thickness of 3 mm is drawn to the final dimension of 20 mm diameter and wall thickness of 2 mm. Metallographic tests on optical microscope, static tensile tests and Vickers hardness tests were used for testing tubes after cold drawing. The hardness change in the deformation zone and the degree of hardening during cold deformation in one draw were examined in detail.