Fe50Ni alloys are used when very high magnetic permeabilities are necessary. Parts of these alloys can be produce by different mechanical processes. Metallurgical processes as investment casting and powder metallurgy can also be used. Sintered Fe50Ni parts have two disadvantages, in terms of magnetic properties: the presence of porosity and the limited grain size. This paper investigates the effects of compactation pressure on the final microstructure and density. Mixtures of atomized iron and carbonyl nickel powder were uniaxially pressed. Cylindrical samples with around 6.5g/cm3 of green density were vacuum sintered at 1220 °C. After sintering samples were cold deformed and then heat treated.
Stainless steels are employed as filters, and in this application the amount of pores and their size distribution are very important. Here it is discussed a densification model, which takes into account both, grain size and density. After this model is applied to experimental data, the obtained parameters can be used for extrapolation in other sintering conditions, for example other temperatures and heating rates. The studied material is the austenitic alloy 316L.
Pre-sintering for removal of lubricants is one of the most important steps in processing of powder metallurgy materials to achieve corrosion resistance. This is often the most neglected step in the sintering process. Incomplete removal of these organic compounds may result in sensitization of sintered parts. The aim of this study is to investigate the effect of lubricant removal process on the corrosion resistance of sintered AISI 304 L stainless steel filters. Pre-sintering was carried out at 450° C and sintering at 1150° C. As lubricant, 1% wax was used. The corrosion resistance of sintered samples was evaluated by polarization and tests, optical and scanning electron microscopy. The results showed that lubricant removal was not complete and during sintering sensitization of the stainless steel occurred decreasing the localized corrosion resistance of the stainless steel.
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