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Wpływ wodoru na mikrostrukturę I wybrane właściwości mechaniczne złączy otrzymywanych metodą wybuchową

Michał Gloc

Abstract

It has been known that long term service of installations in energy and refinery industry in conditions of simultaneous actions of loading and corrosion-hydrogen environments causes degradation of structural steels. One of the economical solutions is to use the corrosion resistance clad materials. Clad plates are usually made of carbon or low alloy steel plates with a thinner layer of stainless steels which offer resistance to various corrosive environments containing hydrogen, in diverse industries like chemical, offshore, petrochemical, petroleum refineries, nuclear, etc. In this work, the investigated clads were obtained by explosive joining. This method is a solid state welding process that is used for the metallurgical joining of dissimilar metals. The process uses forces of controlled detonations to accelerate one metal plate into another in order to create an atomic bond. It is considered as a cold - welding process that allows metals to be joined without losing their pre-bonding properties Hydrogen induces degradation of the microstructure and mechanical properties of structural steels. In the case of ferritic steels, hydrogen may induce blisters with surface microcracks. In the case of clad steels hydrogen may induce underclad cracking and disbonding in the explosion welded plates. In this work, the influence of hydrogen on the microstructure and on the corrosion resistance of three clad plates has been described. The materials used in this study were joints: Carbon steel / austenitic stainless steel (St41k/304L). Carbon steel / nickel alloy (16M/ / INCONEL601). Carbon steel corrosion resistance ferritic steel (St36k/410S). These samples were cathodically charged at room temperature in 0,5M H2SO4 solution containing the hydrogen entry promoter. Light and scanning electron microscopy for microstructure examination was used. It is shown that cathodic hydrogen causes significant changes in the microstructure of the surface (blisters with cracks and microcracks). These microstructural changes lead to a decrease in the stability of the protective film and lower the resistance of pitting corrosion in chloride environment of the tested materials. Adhesion between the parent carbon steel and flyer steel was investigated. Specimens were destructively tested in a bond shear test. Microhardness tests were used to estimate mechanical properties. At the explosive bonded interface between the parent plate steel and the flyer plate stainless steel locally melted zones are formed. These melted zones have a different chemical composition than the bonded materials, a specific structure and in some obtained joints are more resistance to hydrogen degradation. In cladded steels the mechanism of destructive influence of hydrogen on the diffusive bond between flyer and parent plate has a very complex character and is not precisely understood. Significant changes in the microstructure of hydrogen charged specimens (hydrogen corrosion) might occur in flyer plate as well as the base plate, and sometimes also in the bond zone.
Record ID
WUTebf65de1543a459d96218e8286118df4
Diploma type
Doctor of Philosophy
Author
Title in Polish
Wpływ wodoru na mikrostrukturę I wybrane właściwości mechaniczne złączy otrzymywanych metodą wybuchową
Language
(pl) Polish
Certifying Unit
Faculty of Materials Science and Engineering (FMSE)
Discipline
material sciences and engineering / (technology domain) / (technological sciences)
Status
Finished
Start date
14-12-2012
Defense Date
03-07-2014
Title date
03-07-2014
Supervisor
Pages
129
Keywords in English
s
Abstract in English
It has been known that long term service of installations in energy and refinery industry in conditions of simultaneous actions of loading and corrosion-hydrogen environments causes degradation of structural steels. One of the economical solutions is to use the corrosion resistance clad materials. Clad plates are usually made of carbon or low alloy steel plates with a thinner layer of stainless steels which offer resistance to various corrosive environments containing hydrogen, in diverse industries like chemical, offshore, petrochemical, petroleum refineries, nuclear, etc. In this work, the investigated clads were obtained by explosive joining. This method is a solid state welding process that is used for the metallurgical joining of dissimilar metals. The process uses forces of controlled detonations to accelerate one metal plate into another in order to create an atomic bond. It is considered as a cold - welding process that allows metals to be joined without losing their pre-bonding properties Hydrogen induces degradation of the microstructure and mechanical properties of structural steels. In the case of ferritic steels, hydrogen may induce blisters with surface microcracks. In the case of clad steels hydrogen may induce underclad cracking and disbonding in the explosion welded plates. In this work, the influence of hydrogen on the microstructure and on the corrosion resistance of three clad plates has been described. The materials used in this study were joints: Carbon steel / austenitic stainless steel (St41k/304L). Carbon steel / nickel alloy (16M/ / INCONEL601). Carbon steel corrosion resistance ferritic steel (St36k/410S). These samples were cathodically charged at room temperature in 0,5M H2SO4 solution containing the hydrogen entry promoter. Light and scanning electron microscopy for microstructure examination was used. It is shown that cathodic hydrogen causes significant changes in the microstructure of the surface (blisters with cracks and microcracks). These microstructural changes lead to a decrease in the stability of the protective film and lower the resistance of pitting corrosion in chloride environment of the tested materials. Adhesion between the parent carbon steel and flyer steel was investigated. Specimens were destructively tested in a bond shear test. Microhardness tests were used to estimate mechanical properties. At the explosive bonded interface between the parent plate steel and the flyer plate stainless steel locally melted zones are formed. These melted zones have a different chemical composition than the bonded materials, a specific structure and in some obtained joints are more resistance to hydrogen degradation. In cladded steels the mechanism of destructive influence of hydrogen on the diffusive bond between flyer and parent plate has a very complex character and is not precisely understood. Significant changes in the microstructure of hydrogen charged specimens (hydrogen corrosion) might occur in flyer plate as well as the base plate, and sometimes also in the bond zone.
KBN classification
inżynieria materiałowa
Thesis file
  • File: 1
    Gloc.pdf
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Citation count
2

Uniform Resource Identifier
https://repo.pw.edu.pl/info/phd/WUTebf65de1543a459d96218e8286118df4/
URN
urn:pw-repo:WUTebf65de1543a459d96218e8286118df4

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