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  • Open access
  • 108 Reads
Slurry erosion resistance of ferritic X10CrAlSi18 and austenitic AISI 304 stainless steels

Surface degradation due to an interaction of solid particles (erodents) suspended in the liquid medium with an eroded surface is called slurry erosion. Slurry erosion causes an economic problem in many industries like maritime industry, oil and gas extraction and in mining. This type of erosion depends on factors, which are divided into three main categories: operating conditions, properties of eroding particle and target material. In the present work, the slurry erosion tests were performed using a slurry pot tester. X10CrAlSi18 ferritic and AISI 304 austenitic stainless steels were tested in as-received conditions. The erosion tests were performed at impact velocity of 9 m/s and impact angle of 90°. The solid-liquid mixture was prepared by mixing roundness steel solid particles and the concentration of erodents was 12.5%. The purpose of these tests is to compare the erosion resistance of two single-phase steels with different microstructures. The results showed, that AISI 304 steel achieved better erosion resistance than X10CrAlSi18 steel. Final mass losses were about 93% lower. The reason is higher ability of austenitic steel to strain hardening, the strain hardening effect was about 33% and 143% respectively for ferritic and austenitic steels. In both cases, the erosion rate increased to its maximum value, then decreased and remained at a similar level. Taking into account the surface roughness, parameters Ra and Rz decreased with increasing surface hardness. Furthermore, to identify the dominant mechanism of slurry erosion, the erosion efficiency parameter was used, η. The conducted study showed a significant influence of the microstructure and mechanical properties of the eroded material on the erosion resistance.

  • Open access
  • 85 Reads
Electrochemical Characterization and Modeling of Fe-28Mn-6Si-5Cr Shape Memory Steel in Alkaline Medium

A new kind of ferrous SMA, of the Mn family and complemented with Cr additions, the Shape Memory Steel (SMS), is being introduced as a very interesting smart material, able to be used in fitting and reshaping applications, and with the potential of being applied to structural reinforcement applications. It is also more affordable than Ti and Ni based alloys (NiTinol) [1].

This research is focused on the corrosion performance of the Fe‒28Mn-6Si-5Cr Shape Memory Steel. The sample is immersed in a 0,1 M NaOH + 0,1 KOH solution (pH = 13), that mimics the alkalinity of the concrete pore solution. The passive layer formation while exposed to that medium is studied for 7 days by electrochemical means, and its degradation by Cl- additions is also assessed, by progressive additions of Cl- ions in the previouly mentioned solution. This aforementioned layer growth and degradation is modeled by different equivalent circuits. The evolution of the system behavior is monitored.

Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No769255. This document reflects only the views of the authors. Neither the Innovation and Networks Executive Agency (INEA) nor the European Commission is in any way responsible for any use that may be made of the information it contains

  • Open access
  • 80 Reads
Corrosivity of different natural groundwaters from repository sites

In Finland, the repositories for low and intermediate-level waste (LLW and ILW) are situated at three different geographical locations in deep granite bedrock where the waste containers can be subjected to anoxic groundwater containing microbes. The composition of groundwater varies in terms of chemistry and microbial activity in different locations. In this study, groundwater from three repository areas was analyzed in respect of chemistry and microbial community. Corrosion tendency of three steel grades, carbon steel AISI/SAE 1005 and stainless steels AISI 304 and 316L, was studied in these groundwater environments using electrochemical methods. As a reference, measurements were also performed in simulated groundwater without microbes. The measurements show that corrosivity of the water and thus the steels’ performance differs depending on its location of origin. Also, the groundwater differed remarkably in in their chemical composition as well as abundance and diversity of microbial community. Consequently, the local environment has to be considered when evaluating the long-term safety of disposal of nuclear waste.

  • Open access
  • 216 Reads
Effect of indium chloride on corrosion of Mg under polarization

Magnesium is a light weight, relatively low cost and Earth abundant material. The advantageous properties of Mg increase its usage in different areas, including batteries. Aqueous Mg-air primary batteries represent one class of promising power sources for multiple applications. However, during the discharge Mg anode is prone to self-corrosion with formation of an insoluble film of magnesium hydroxide and generation of hydrogen. The possible solution for enhancement of battery performance is addressing the Mg electrode-electrolyte interface by appropriate additives, that serve as corrosion inhibitors for the suppression of the Mg self-corrosion and that prevent the formation of blocking precipitates, Mg(OH)2. In this work, we studied the effect of InCl3 as effective additive, which at low concentrations reduce the self-corrosion of Mg electrode. The performance of InCl3 was investigated by EIS measurement and in-situ local simultaneous measurement of pH with concentration of dissolved oxygen. InCl3 was capable of retarding electrolyte alkalization during polarization due to its hydrolysis reaction, which leads to less film-relevant potential drop. Nevertheless, insufficient amount of In3+ addition also shows pH buffering effect for the bulk environment, but is not able to hinder the increase of local pH.