The article is devoted to complex studies of diamond-like coatings applied by the PAPVD technique to improve the surface of medical tools and implants in terms of better anticorrosive behaviour and biocompatibility. By means of scanning microscopy, the micromechanical properties of coatings were examined as well as their adhesion to the metallic substrate and structure of the coating-metallic substrate interface. Corrosion resistance and biocompatibility of coatings were also tested. An attempt was made to improve the gripping capacity of surgical vises used for laying down of suture in vascular surgery through application of an appropriate layer of nickel-diamond composite on the gripping part of the tool. Thus modified tools were next tested for mechanical properties. The results of performance tests of the vises enabled evaluating the gripping part of the tool as holding firm the surgical needle without the least changing of its position and tearing of the thread. The results of the tests carried out on vises were confirmed by opinions of the surgeons.
Keywords: medical tools, implants, biocompatibility, adhesion, corrosion, diamond-like coating, diamond layers,
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Franciszek Pezarski, Elżbieta Smoluchowska, Irena Izdebska-Szanda
The article presents the results of laboratory and industrial tests on the application of a new geopolymer Rudal A binder used in production of moulding and core sands for castings from carbon and alloyed cast steels and from cast iron. The new binder contains an inorganic polymer based on silicon and aluminium. After hardening the sand with this binder is characterised by high strength and permeability, low viscosity (easy cleaning of the tooling) and low humidity, compared with sands containing sodium silicate. The binder in composition with proper hardener is applicable in the technology of loose self-setting sands. It is also suitable in preparation of moulding and core sands hardened with CO2. Owing to the use of proper hardener there is a vast range of possibilities to control the binding rate of self-setting sands. Besides the above mentioned advantages, the content of binder in the sand is much lower than in the sands with sodium silicate, which reduces the binder cost on purchase. The sand offers very good knocking out properties and reclamability. Application of the new binder in the technology of self-setting and CO2 hardened sands improves the work conditions and environmental protection, compared with the sodium silicate-based sand technology and sands with organic binders.
Keywords: inorganic binder, geopolymer Rudal A binder, seft-setting sands, sands hardened with CO2, moulding and core sands, reclamation, knocking out properties,
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Adam Tchórz, Łukasz Boroń, Marzanna Książek
The study presents the results of structure examinations and mechanical tests carried out on coatings based on Cr3Cr2-NiCr chromium carbide, applied onto the surface of ductile iron castings. The chromium carbide-based coatings were applied onto the cast iron substrate by the technique of plasma spraying. Then the coatings were subjected to a remelting treatment. The chemical composition and morphology of the surface layer were examined by optical microscopy and by SEM with EDS analysis. The distribution of microhardness values on the specimen cross-section was determined and cyclic fatigue testing was carried out. Basing on the results of the tests it has been concluded that remelting of Cr3Cr2-NiCr coating improves its adherence to the substrate as well as the structure and mechanical properties under the conditions of variable loading. The investigations mainly aimed at the development of technical guidelines for manufacture of protective coatings on ductile iron castings operating under the conditions of heavy dust and cyclic loading.
Keywords: plasma spraying, remelting, ductile iron,
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Żółkiewicz Zdzisław, Żółkiewicz Marek
One of the main parameters that determine the correct run of pattern evaporation process is the type and volume of gas evolved from a foamed polystyrene pattern during its evaporation. The process of pattern evaporation takes place within a preset range of temperatures. The volume of the evolved gas depends on the temperature, and on the pattern volume and weight. One of the gaseous products of the foamed polystyrene pattern decomposition is hydrogen. Its content in the total volume of the evolved gas depends on the temperature at which the pattern evaporation takes place. Maximum hydrogen content in the total volume of gas may reach even 10%. In the present studies the effect of the products of the thermal decomposition of a foamed polystyrene pattern on the metal properties, especially on the content of hydrogen in this metal, was determined. The content of hydrogen was determined in grey iron samples obtained by the lost foam process. The tentative results of the investigations were plotted in the form of diagrams.
Keywords: casting, pattern, pattern made of foamed polystyrene, temperature, evaporation,
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Franciszek Pezarski, Irena Izdebska-Szanda, Elżbieta Smoluchowska
The article gives the results obtained in a fragment of the studies, carried out under a statutory activity, on optimising of the foundry sand technology with new modified inorganic binders, chemically bonded and CO2 hardened. The presented results of the investigations of the self-setting sands with new inorganic binders show the character of changes in basic technological parameters in function of the time and a variable content of the binding agents, allowing also for the important - from the foundry’s point of view - effect of ambient conditions, i.e. temperature and humidity, on the kinetics of the sand binding. In the case of CO2 hardened sands, special attention was paid to the phenomenon of friability of these sands, which is considered an indication of the mould and core surface quality, and as such has an important effect on the quality of final products when fabricated under the industrial conditions.
Keywords: inorganic binders, modification, strength, bench life, friability,
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