Wpływ krzemu na proces spiekania oraz właściwości austenitycznej stali nierdzewnej AISI 316L

Agnieszka Szymańska

Abstract

Austenitic-ferritic stainless steels are increasingly used all over the world because of their good stress corrosion resistance. For some time, they have also been of interest in Poland. Since their mechanical strength is higher than that of austenitic steels, the constructions and devices made of them may be lighter. Moreover, because of the lower content of alloying additives, especially nickel, they should be less expensive. The technology of austenitic-ferritic steels is however more difficult than that of traditional ferritic and austenitic steels. Most of these difficulties can be obviated by using powder metallurgy, but water –dispersed powders of autenitic-ferritic steels resistant to corrosion are not available on the home market even though this technology arouses wide interest in the industry. In the present study an attempt was made at producing two-phase steel by sintering a stainless AISI 316L steel powder with a silicon powder. The powder mixtures with the addition of the silicon powder ranging from 0 to 7wt.% were pressed under uniaxial pressure of 600MPa and then sintered at a temperature of 1240oC in a hydrogen atmosphere for 1h. The structure, mechanical properties and chemical properties of the sinters thus obtained were thoroughly examined. It has been shown that, during sintering, the silicon powder, added to the basic AISI 316L austenitic steel powder in an amount of above 3wt.%, destabilizes partially the austenite, which results in the formation of a ferritic phase. It is therefore possible to produce sinters with an austenitic-ferritic structure using a classical process of pressing and pressure-less sintering at low production costs. The share of ferrite in the sinters appear to increase with increasing silicon content and, with 7wt.% of silicon, it reaches a maximum of 55%. Moreover, an addition of silicon of 5wt% or more increases considerably the relative density of the sinters compared to that of sinters composed of AISI 316L steel alone. The highest tensile strength was achieved in the sinters with a 5wt% silicon content. These sinters may, therefore, have practical importance.
Diploma typeDoctor of Philosophy
Author Agnieszka Szymańska (FMSE)
Agnieszka Szymańska,,
- Faculty of Materials Science and Engineering
Title in PolishWpływ krzemu na proces spiekania oraz właściwości austenitycznej stali nierdzewnej AISI 316L
Languagepl polski
Certifying UnitFaculty of Materials Science and Engineering (FMSE)
Disciplinematerial sciences and engineering / (technology domain) / (technological sciences)
Defense Date24-09-2010
Supervisor Krzysztof Sikorski (FMSE / DMD)
Krzysztof Sikorski,,
- Division of Materials Design

Internal reviewers Waldemar Kaszuwara (FMSE / DCFM)
Waldemar Kaszuwara,,
- Division of Construction and Functional Materials
External reviewers Józef Nowacki
Józef Nowacki,,
-
Pages107
Keywords in Englishxxx
Abstract in EnglishAustenitic-ferritic stainless steels are increasingly used all over the world because of their good stress corrosion resistance. For some time, they have also been of interest in Poland. Since their mechanical strength is higher than that of austenitic steels, the constructions and devices made of them may be lighter. Moreover, because of the lower content of alloying additives, especially nickel, they should be less expensive. The technology of austenitic-ferritic steels is however more difficult than that of traditional ferritic and austenitic steels. Most of these difficulties can be obviated by using powder metallurgy, but water –dispersed powders of autenitic-ferritic steels resistant to corrosion are not available on the home market even though this technology arouses wide interest in the industry. In the present study an attempt was made at producing two-phase steel by sintering a stainless AISI 316L steel powder with a silicon powder. The powder mixtures with the addition of the silicon powder ranging from 0 to 7wt.% were pressed under uniaxial pressure of 600MPa and then sintered at a temperature of 1240oC in a hydrogen atmosphere for 1h. The structure, mechanical properties and chemical properties of the sinters thus obtained were thoroughly examined. It has been shown that, during sintering, the silicon powder, added to the basic AISI 316L austenitic steel powder in an amount of above 3wt.%, destabilizes partially the austenite, which results in the formation of a ferritic phase. It is therefore possible to produce sinters with an austenitic-ferritic structure using a classical process of pressing and pressure-less sintering at low production costs. The share of ferrite in the sinters appear to increase with increasing silicon content and, with 7wt.% of silicon, it reaches a maximum of 55%. Moreover, an addition of silicon of 5wt% or more increases considerably the relative density of the sinters compared to that of sinters composed of AISI 316L steel alone. The highest tensile strength was achieved in the sinters with a 5wt% silicon content. These sinters may, therefore, have practical importance.
Thesis file
Szymanska.pdf 5.65 MB
Citation count*5 (2020-09-26)

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