ZMIANY WYMIAROWE, MIKROSTRUKTURA, ROZKŁAD MIKROTWARDOŚCI I WŁASNOŚCI KOROZYJNE SPIEKANYCH MATERIAŁÓW ŻELAZO ORAZ ŻELAZO-MANGANIron samples and Fe-Mn alloys with Mn content of 25 wt.% and 30 wt.% were prepared by blending, compressing and sintering with the aim to study their dimensional changes, microstructure, microhardness distribution and primarily the electrochemical corrosion behaviour in a simulated body environment.The light microscopy (LM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and microhardness measurements revealed a microheterogeneous multiphase structure of sintered Fe-Mn samples. The potentiodynamic tests have demonstrated that the corrosion rates of such Fe-Mn alloys immersed in Hank's solution were higher than those for a pure iron, and also higher than the rates reported for homogeneous Fe-Mn alloys.Keywords: powder metallurgy, iron, manganese, corrosion behaviour, dimensional changes, microhardnessPróbki żelazne oraz stopy Fe-Mn, zawierające 25 i 30% mas. Mn, przeznaczone na biomateriały, zostały przygotowane na drodze mielenia, prasowania oraz spiekania w celu zbadania ich zmian wymiarowych, mikrostruktury, rozkładu mikrotwardości oraz odporności korozyjnej w skumulowanych w warunkach laboratoryjnych, panujących w ciele człowieka. Badania z wykorzystaniem mikroskopii optycznej i skaningowej, wraz z EDX oraz pomiary mikrotwardości ujawniły mikroniejednorodność wielofazowej struktury spiekanych stopów Fe-Mn. Testy potentiometryczne wykazały, że współczynniki korozji spieków Fe-Mn były wyższe niż spieków wykonanych z czystego żelaza oraz z jednorodnych stopów Fe-Mn.
Particles of iron powder were electrolytically coated with a copper and subsequently with a hydrocarbon. Coated powder was compressed into cylindrical samples at 600 MPa and sintered at 1120°C. Using Microhardness Tester LECO LM-700AT, Vickers microhardness of samples has been investigated by indenting the unetched metallographic polished section. Test loadings were 10g, 25g, 50g, 100g, 200g, 300g, 500g and 1000g. Loading time was set on 10 seconds. It was found that there are different values of microhardness within a grain. Microhardness measurements taken at different points in the specimen enabled us to map the occurrence of various hardness values, which reflects a variety of the local microstructure of the examined material. At large loading, effective properties of a large volume of material are measured and the range of measured hardness narrows. ISE was observed.
Iron was considered a good material candidate for temporary implants in cardiovascular and orthopedic surgery. Mechanical properties of iron are attractive, however, a higher degradation rate is required. The contribution deals with the effect of silver content on microstructure and corrosion behavior of materials prepared from Ag coated iron powders. Using electroless deposition, Fe-powders with 0.29 and 2.1 wt.% of silver were prepared. Cylindrical specimens compacted at a pressure of 200 MPa were isothermally sintered at 1120°C for 60 min. The microstructure of the sintered specimens consisted of iron matrix with Ag-precipitates. The corrosion behaviour of sintered compacts was studied using the potentiodynamic polarization technique in Hank’s solution and complemented with SEM analysis. It was found out that corrosion resistance of material decreased with an increase in silver content.
The current trend in development of new metallic materials for certain types of implants is turning away from permanent, biologically inert materials to the use of biodegradable materials. Fe–Mn alloys represent high perspective material for development of new generation of temporary and biodegradable implants. The aim of this work was to study mechanical and corrosion characteristics of powder samples containing 25, 30 and 35 wt % of Mn which are fabricated by pressing, sintering, and additional spark plasma sintering. The influence of preparation method (pressing and sintering) to microstructure, phased composition and corrosion behavior of prepared alloys was studied.
Powders comprised of Fe particles and 25, 30, 35wt.% of Mn particles were mixed, compacted and sintered to investigate the effect of Mn on the properties of sintered Fe-Mn alloys. It was found that the sample’s swelling, microstructure and distribution of local hardness values were strongly affected by the Mn content. The particles in Fe-25Mn and Fe-30Mn samples exhibited a distinct onion-like structure causing a considerable variability in local properties, while the particles in Fe-35Mn samples were at a glance more homogeneous, with a large volume fraction occupied by a nearly uniform material with almost constant properties.
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