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Aluminium-alloyed austenitic steels Fe-14Cr-2Mn-20Ni-0.5Cu-3Al and Fe-14Cr-5Mn-12Ni-3Cu-2.5Al were tested at 500 °C in static Pb-Bi eutectic for 10,000 h. The concentration of oxygen in the liquid metal was changed in a controlled way over the course of the test from ∼10−6 to ∼10−9 mass% which provided conditions for oxidation and dissolution, respectively. Both steels showed slight oxidation of surface. Steel with higher Ni content revealed also initiation of dissolution corrosion in the view of rare pit-type damages. The structural and compositional features of oxide films, sub-oxide zones and corrosion damages are discussed.

This work addresses the effect of deformation twinning on the dissolution corrosion behaviour of 316 L austenitic stainless steels in contact with static liquid lead-bismuth eutectic (LBE). For this purpose, plastically deformed 316 L steel specimens with distinctly different deformation twin densities were simultaneously exposed to oxygen-poor (

This study addresses the effect of plastic deformation on the dissolution corrosion behavior of a Type 316L austenitic stainless steel. Dissolution corrosion was promoted by low oxygen conditions in liquid lead-bismuth eutectic (LBE). Specimens with controlled degree of plastic deformation (20%, 40%, and 60%) and a non-deformed, solution-annealed specimen were simultaneously exposed for 1,000 h at 500°C to static LBE with low oxygen concentration ([O] < 10−11 mass%). The corroded specimens were analyzed by various material characterization techniques. All exposed specimens exhibited dissolution corrosion. The non-deformed steel showed the least dissolution attack (maximum depth: 36 μm), while the severity of attack increased with the degree of steel deformation (maximum depth in the 60% steel: 96 μm). It was, thus, concluded that increasing the amount of plastic deformation in a Type 316L stainless steel results in higher dissolution corrosion damages for steels exposed to low oxygen LBE conditions. Addit...

Cracking jumps were observed in notched T91 (9Cr-1Mo ferritic-martensitic steel) specimens tested in liquid lead-bismuth eutectic (LBE) at 350 °C under tensile loading. The cracking jumps manifested themselves as being regular steps at tensile curves, while as being fatigue striation-like markings at fracture surfaces. The markings were consisted of liquid metal embrittlement (LME) zones and ductile zones. The liquid LBE was adsorbed at crack tip and likely reduced the interatomic bonding strength, leading to cracking in a brittle way and release of elastic energy in the load line. This unique phenomenon was found to be associated with coupled effects of LME and compliance/stiffness of tensile machines.

The influence of displacement rate and temperature on the severity of liquid metal embrittlement (LME) was investigated by performing fracture toughness tests on the ferritic-martensitic T91 steel in liquid lead-bismuth eutectic (LBE) at three different displacement rates at 200 °C and 350 °C. Compact tension specimens were used for testing and all specimens were pre-cracked in LBE environment at 350 °C prior to testing. The energy normalization (EN) method was used to construct the J-R curves. J Q of each specimen was calculated and the fracture surfaces were investigated by scanning electron microscope (SEM). The results were compared to the tensile test results of the same material where reduction in total elongation was used to determine the susceptibility to LME. Comparison of tests at 200 °C and 350 °C showed that the LME effect was less prominent at 200 °C which was evidenced by the higher J -values obtained at this temperature and the fracture surfaces which overall had a significant distribution of dimples and larger secondary cracks. The observation of reduced LME effect at lower temperature was found to be in accordance with the tensile data within the strain rates discussed in this paper. Although the tensile test results show reduced LME effect as the strain rate is sufficiently reduced at 350 °C, the fracture toughness tests point to a more severe LME effect with decreasing displacement rate. An LME mechanism of T91 in LBE was discussed based on the observations given in this work. The fracture toughness values in LBE were found to be very low to support the selection of T91 material for the LBE cooled nuclear reactors. Moreover, as the obtained toughness values do not reflect the conservative estimation of the LME effect, incorporation of LME in the design of such reactors is not feasible in the current state.

Long-term corrosion behavior of T91 ferritic/martensitic steel in oxygen-doped flowing Pb–Bi eutectic is investigated by exposure for up to 20,000 h at 400 °C, 2 m/s and 2 × 10−7mass% dissolved oxygen. The corrosion phenomena and kinetics of interaction are characterized qualitatively and quantitatively. The steel shows major oxidation resulted in the formation of a bilayer Fe3O4 / Fe(Fe,Cr)2O4 scale. After 20,000 h, the scale thickness averages 12.6 (±2.7) μm. The metal recession due to oxidation does not exceed 5 (±1) μm. Besides oxidation, the localized dissolution of the steel is observed reaching of ∼100 μm in depth after 20,000 h.

T91 ferritic-martensitic steel is one of the candidate materials to future fast reactors where lead-bismuth eutectic (LBE) is chosen as the coolant. The interaction of the steel with LBE coolant should be investigated by means of mechanical tests and detailed microstructural analysis. Quantitative analysis requires fracture toughness tests in LBE. However tests in LBE are not easily applied with conventional methods due to the conductive nature of LBE. In addition, there are no standards or guidelines for fracture toughness tests in LBE. In this work fracture toughness tests in inert environment and LBE are compared and technical problems encountered during tests in LBE are discussed.

Liquid metal embrittlement (LME) induced quasi-brittle fracture characteristics of a 9Cr–1Mo ferritic–martensitic steel (T91) after fatigue cracking in lead–bismuth eutectic (LBE) have been investigated at various length scales. The results show that the LME fracture morphology is primarily characterized by quasi-brittle translath flat regions partially covered by nanodimples, shallow secondary cracks propagating along the martensitic lath boundaries as well as tear ridges covered by micro dimples. These diverse LME fracture features likely indicate a LME mechanism involving multiple physical processes, such as weakening induced interatomic decohesion at the crack tip and plastic shearing induced nano/micro voiding in the plastic zone.