A refined oxidation mechanism proposed for ferritic-martensitic steels exposed to oxygen-saturated liquid lead-bismuth eutectic at 400°C for 500 h

Si segregation and relevant effect on the corrosion propagation in F/M steel exposed to liquid lead-bismuth eutectic

“…Spinel particles and surrounded matrix have a Bake-Nutting relationship, i.e. {001} spinel // {001} matrix and , 100. spinel // , 100. matrix , consistent with the literature [9,10,15]. EDS mappings reveal that the oxide precipitates in IOZ are enriched in Cr, but depleted in Fe.…”

“…IOZ, characterised by the presence of dark intermetallic compounds uniformly distributing in the matrix (shown in Figure 3(b)), has widely been reported in F/M steel exposed to oxygen-saturated LBE environment [9 11]. Figure 3(b) shows the high angle annular dark field scanning TEM (HAADF-STEM) image and corresponding elemental distribution mapping of IOZ, which is composed of oxide precipitates and ferrite matrix.…”

“…Ye et al [9] proposed the micron-scale and nano-scale diffusion of Cr in IOZ during the internal oxidation and a refined oxidation mechanism including the internal oxidation and the conversion of IOZ to the inner oxidation layer. Xiao et al [10] suggested that oxygen diffused along the Pb nano-channels in Fe 3 O 4 and continued to diffuse inward along the hyperfine grain boundaries in Fe-Cr spinel before arriving at the nano-voids. One part of the arrived oxygen preferentially oxidised the grain boundaries and martensitic lath boundaries to form chromium oxide (Cr 2 O 3 ), and the other part reacted at nano-voids to form Fe-Cr spinel.…”

Environmental degradation of structural materials in liquid lead- and lead-bismuth eutectic-cooled reactors

“…The outer oxide scale layer is invariably magnetite (i.e., Fe 3 O 4 ), while the inner oxide scale layer varies, depending on the steel composition (i.e., Fe(Fe,Cr) 2 O 4 spinel, Cr 2 O 3 , SiO 2 , and/or Al 2 O 3 ). The outer magnetite layer is usually rather porous and will, thus, be infiltrated by the HLM within a certain period of time; in the case of liquid LBE, the HLM penetration appears to be a Pb-based solid solution made of >90 at.% Pb and a small amount of Bi [110]. The inner oxide scale layer is typically more protective than the outer magnetite layer, and its growth into the steel bulk is often preceded by the establishment of an IOZ † at its growth front.…”

“…The inner oxide scale layer is typically more protective than the outer magnetite layer, and its growth into the steel bulk is often preceded by the establishment of an IOZ † at its growth front. The IOZ is usually made of a Cr-based oxide (e.g., Cr 2 O 3 ) that develops preferentially at martensitic lath boundaries [110]. It should be added that it has not yet been clarified whether the inner oxide layer is magnetite (an inverse spinel structure) with dissolved Cr or a Cr-deficient FeCr-spinel (FeCr 2 O 4 ).…”