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EN
Variable energy positron beam and positron lifetime spectroscopy were used to study pure silver samples exposed to irradiation with swift Xe²⁶⁺ ions of energy 167 MeV with different dose: of 10¹³, 5×10¹³ and 10¹⁴ ions/cm². The positron lifetime spectroscopy revealed the presence of dislocations or vacancies associated with dislocations. They are distributed at the depth of about 6 μm, and this correlates with the ion implantation range, i.e. 9 μm. However, some defects are observed also to a depth of about 18 μm. At the depth less than 1 μm from the entrance surface strong dependence of positron diffusion length on the dose is observed. It indicates the presence of interstitial atoms and/or dislocation loops as a result of Xe²⁶⁺ ions implantation.
EN
The determination of fracture toughness of aluminium alloy aviation parts, exposed to cyclic mechanical loading, is an important engineering issue. The service life and crack resistance of such unprotected metallic parts is limited under corrosive operating conditions. The resistance against fracture cracking and corrosion resistance can be increased by the surface coatings. The scientific research of fracture toughness of coated metallic parts is being carried out in a comprehensive way. In this research, fracture toughness behaviour of high velocity oxy-fuel (HVOF) spray coated and conventional hard chrome plated aluminium-zinc alloy parts were compared and the results are discussed. The fracture surfaces are investigated and fracture toughness values are calculated. Electron microscopy analysis revealed significant differences in crack growth morphology and toughness values. As a result, the fracture toughness value is higher in hard chrome plated parts.
EN
The effect of nitrogen ion implantation on Stellite 6 cobalt alloy was investigated. In this research, cobalt alloy was implanted with 65 keV nitrogen ions at the fluence of (1÷10)×10¹⁶ N⁺/cm². The distribution of implanted nitrogen ions and vacancies produced by them was calculated using the SRIM program. The surface morphology was examined and the elemental analysis was performed using scanning electron microscopy, energy dispersive X-ray spectroscopy and grazing incidence X-ray diffraction. The wear tests were conducted with the use of the pin-on-disc method. The results demonstrate that implantation with nitrogen ions significantly reduces the friction factor and wear. The friction coefficient of the implanted sample at the fluence of 1×10¹⁷ N⁺/cm² increased to the values characteristic of an unimplanted sample after 5000 measurement cycles. The depth of the worn trace was about 2.0 μm. This implies that the thickness of the layer modified by the implantation process is ≈2.0 μm and exceeds the initial range of the implanted ions by an order of magnitude. This is referred to as a long-range implantation effect. The investigations have shown that the long-range effect is caused by movement of not only implanted nitrogen atoms but also carbon dopant atoms towards the friction zone. Diffusion of carbon atoms has been documented here for the first time. Furthermore, the increased content of oxygen atoms on the track bottom indicates a dominant oxidative wear of the Stellite samples after nitrogen implantation with the energy 65 keV and the fluences of 5×10¹⁶ and 10¹⁷ N⁺/cm².
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