Papers by Author: Jan Kazior

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Authors: Alberto Molinari, Cinzia Menapace, Jan Kazior, Tadeusz Pieczonka
Abstract: It is well known that PM stainless steels have lower corrosion resistance than the corresponding wrought steels, since they are affected by the presence of the open porosity. A way to obtain a surface densification is the addition of a small quantity of boron (from 0,3 to 0,5%wt.) to the stainless steel. The presence of boron produces a liquid phase phenomenon that results in a final microstructure consisting of a boron-rich phase network surrounding the stainless steels grains. Close to the surface, a boron-free layer was observed in which pores are very few, closed and round. This leads to an improvement in the steel corrosion resistance.
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Authors: K. Sikorski, Agnieszka Szymańska, M. Sekuła, D. Kowalczyk, Jan Kazior, Krzysztof Jan Kurzydlowski
Abstract: The aim of the study was to obtain a ferritic-austenitic stainless steel through sintering of the mixture of austenitic steel AISI 316L powders with silicon in the amount ranging from 1 to 7%. The pressed mixtures were sintered at 1240oC for 60 minutes under hydrogen atmosphere. The results of the silicon admixture on the density, porosity, microstructure and mechanical properties of the sintered specimens are discussed.
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Authors: Tadeusz Pieczonka, Jan Kazior
Abstract: High purity aluminium powder was sintered in a dilatometer in flowing high purity nitrogen. The distinct shrinkage segments observed on the dilatometry curves were the basis of experiments consisting of interrupted sintering. In this way compacts with microstructure frozen at different steps of sintering cycle were produced. Optical microstructure examinations and LECO analysis of nitrogen content showed the development of aluminium nitriding. Additionally, X-ray diffraction was used to examine phases appearing in the system investigated. Microstructure analysis of structural components revealed evidence that isothermal sintering proceeds in the presence of a liquid phase, despite taking place below the melting point of aluminium. It seems that aluminium nitrogen interactions are responsible for the appearance of this phase, which is accompanied by extensive shrinkage.
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Authors: Jan Kazior, Aneta Szewczyk-Nykiel, Tadeusz Pieczonka, Marek Hebda, Marek Nykie
Abstract: Alloys from austenitic and ferritic stainless steel found to be satisfactory for a great many applications. However, for applications that require higher levels of strength and hardness from the martensitic grades are frequently specified. Martensitic stainless steels offer significantly higher strengths but have to low ductility. For this reason for application where high levels of strength and a moderate ductility is required, the precipitation strengthened stainless steels are often considered. One of the most popular alloy of this kind of stainless steel is 17-4 PH. The aim of the present paper was to examined the influence the process parameters in conventional powder metallurgy processing on the mechanical properties of the 17-4 PH alloy in both as-sintered and heat treated conditions. In was found that temperature of aged is a very sensitive parameter for obtained high strength and acceptable ductility.
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Authors: Tadeusz Pieczonka, Jan Kazior
Abstract: The sinter-bonding behavior of iron based powder mixtures was investigated. To produce the green compacts to be joined the following powders based on Höganäs AB grade NC 100.24 plain iron powder were used: NC 100.24 as delivered, PNC 30, PNC 60 and NC 100.24 + 4%Cu powder mixtures. Dimensional behaviour of all those materials during the sintering cycle was monitored by dilatometry. Simple ring shaped specimens as the outer parts and cylindrical as the inner parts were pressed. The influence of parts’ composition on joining strength was established. Diffusion of alloying elements: copper and phosphorous, across the bonding surface was controlled by metallography, SEM and microanalysis.
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Authors: Agnieszka Szymańska, Krzysztof Sikorski, Jan Kazior
Abstract: The article illustrates the influence of ball milling of the 316L and 434L stainless steel powders as well as their mixture (50 wt. % of 434L + 50 wt. % of 316L) on their structure. Medium size of the grains (about 30 nm) was obtained after 110 hours of milling. The powders that obtained were pressed isostatically and sintered by impulse plasma method in vacuum. The samples were then characterized using an optical microscope equipped with a computer image analyzer, scanning electron microscope and X-ray diffractometer.
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