Review article
Influence of microstructure on the resistance of tool steels to local corrosion in 3.5% NaCl medium
Anita Begić Hadžipašić
; University of Zagreb Faculty of Metallurgy
Sandra Brajčinović
; University of Zagreb Faculty of Metallurgy
Marija Rajković
; University of Zagreb Faculty of Metallurgy
Abstract
In this research, electrochemical and metallographic tests were carried out on tool steel for cold and hot work, as well as steel for cementation, with the goal to obtain corrosion parameters to determine which of the examined samples is more resistant to local pitting corrosion. Electrochemical tests were performed in a medium of 3.5% NaCl, and were based on conducting cyclic anodic polarization in the potential range from -2000 mV to 200 mV vs SCE and vice versa. The results of the research showed that all three samples are subject to pitting corrosion, but the worst was the cementing tool steel sample X19NiCrMo4, which had the lowest pitting potential. The W600 tool steel sample for hot work
proved to be the best, with the highest pitting potential. The results of the electrochemical tests coincide with the metallographic tests, because after corrosion in the chloride medium only the beginnings of pitting corrosion are visible on the surface of the W600 sample in the form of partial accumulations of corrosion products, while the X19NiCrMo4 cementing steel sample was completely covered with corrosion products, which means that of the three tested tool steels, cementing steel is the most susceptible to pitting corrosion and is not recommended for use in conditions where it comes into contact with chloride ions. The martensitic microstructure of cementing tool steel is responsible for the very low pitting potential and, consequently, pronounced pitting corrosion. On the other hand, the W600 tool steel showed better corrosion resistance due to its finer grain and uniform carbide distribution.
Keywords
pitting corrosion, tool steels, cyclic anodic polarization, 3.5% NaCl, microstructure
Hrčak ID:
302318
URI
Publication date:
16.5.2023.
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