Abstract
The pitting corrosion resistance and passive behavior of type 304 borated stainless steels (Febalance–18Cr–12Ni–1.5Mn–(0.19, 0.78, and 1.76 wt %)B) manufactured through conventional ingot metallurgy were investigated. The alloys were composed of an austenitic matrix and Cr2B phase, and the volume fraction of Cr2B increased from 1.68 to 22.66 vol % as the B content increased from 0.19 to 1.76 wt %. Potentiodynamic polarization tests measured in aqueous NaCl solutions revealed that the pitting corrosion resistance was reduced as the B content increased and the pits were initiated at the matrix adjacent to the Cr2B phase. It was found that the reduced resistance to pitting corrosion by B addition was due to the formation of more defective and thinner passive film and increased pit initiation sites in the matrix.
Highlights
Boron (B)-containing austenitic stainless steels known as borated stainless steels (BSSs) have been widely used in the nuclear industry primarily due to their excellent thermal neutron attenuation capability
The present paper aims to investigate the passive behavior and the resistance to passivity breakdown of type 304 stainless steels (Febalance 18Cr12Ni1.5Mn-based alloys, in wt %) containing 0.19–1.76 wt % B, which were manufactured through conventional ingot metallurgy
The resistance to pitting corrosion and passive behavior of type 304 stainless steels (Febalance 18Cr12Ni1.5Mn-based alloys, in wt %) containing 0.19–1.76 wt % B, which were manufactured through conventional ingot metallurgy, were investigated
Summary
Boron (B)-containing austenitic stainless steels known as borated stainless steels (BSSs) have been widely used in the nuclear industry primarily due to their excellent thermal neutron attenuation capability. Because the neutron absorption ability directly relies on the B content in the materials [3,6,8,10], the BSS should contain as much B as possible to be safely used as wet storage rack materials for spent nuclear fuel. The solubility of B in the austenitic stainless steels is very limited—as low as approximately 100–150 ppm depending on the matrix composition [9,13,19]; the addition of an excessive amount of B inevitably forms M2 B (M stands for metal; Cr and/or Fe) type phase, which is known to degrade the mechanical and corrosion properties [4,5,6,7,8,13,20]. Loria et al [13] reported the general corrosion behavior and intergranular corrosion susceptibility of type 304 stainless steel with 0.5 wt % B and without B in Materials 2018, 11, 2097; doi:10.3390/ma11112097 www.mdpi.com/journal/materials
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