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The role of the weak points in the corrosion resistance of hydrostatically extruded steel porducts
|Dominika Klassek 4, Thomas Suter 2, Waclaw Pachla 3, Krzysztof J. Kurzydlowski 4, Oliver von Trzebiatowski 2, Mariusz Kulczyk 3,4
1. Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland
Hydrostatic extrusion (HE) can be used to produce nanostructured materials by applying high hydrostatic pressure, to obtain a homogenous microstructure within entire volume of the processed material. Hydrostatically extruded materials exhibit significant increase in the mechanical properties such as hardness and yield stress. The goal of this project is to achieve also an improvement in corrosion resistance of the 316LVM stainless steel by decreasing the grain size down to the nanometer scale by applying HE.
The corrosion behaviour of 316LVM steel has been examined in NaCl solutions with different chloride concentrations. Large scale polarization and etching tests showed that the corrosion resistance of hydrostatically extruded 316LVM steel decreased in comparison to as received specimens. Etching test in VA2 solution indicated that additional weak points, other than MnS inclusions, could be present in the microstructure. They might be related with stresses introduced during HE. In order to relax this stresses, hydrostatically extruded steel has been annealed. Small area measurements in different zones on the rod specimens were carried out in order to find out which weak points are responsible for the corrosion resistance of 316LVM steel. No significant change between centre and edge of the rods was observed. However, preliminary tests performed on cross sections parallel to the HE direction, showed improved corrosion behaviour compared to the measurements performed perpendicular to the HE direction. These results indicate, that MnS inclusions which were deformed during HE, might trigger the onset of corrosion on 316LVM steel.
Presentation: oral at E-MRS Fall Meeting 2005, Symposium I, by Dominika Klassek
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-20 08:08 Revised: 2009-06-07 00:44