Report on sodium compatibility of advanced structural materials.

Li, M. ; Natesan, K. ; Momozaki, Y. ; Rink, D.L. ; Soppet, W.K. ; Listwan, J.T. (Nuclear Engineering Division)

Argonne National Laboratory

关键词: Building Materials;    Alloys;    Strain Aging;    Forced Convection;    Strain Softening;   

DOI  :  10.2172/1045757
RP-ID  :  ANL-ARC-205
RP-ID  :  DE-AC02-06CH11357
RP-ID  :  1045757

美国|其它

来源: UNT Digital Library

【 摘 要 】

This report provides an update on the evaluation of sodium compatibility of advanced structural materials. The report is a deliverable (level 3) in FY11 (M3A11AN04030403), under the Work Package A-11AN040304, 'Sodium Compatibility of Advanced Structural Materials' performed by Argonne National Laboratory (ANL), as part of Advanced Structural Materials Program for the Advanced Reactor Concepts. This work package supports the advanced structural materials development by providing corrosion and tensile data from the standpoint of sodium compatibility of advanced structural alloys. The scope of work involves exposure of advanced structural alloys such as G92, mod.9Cr-1Mo (G91) ferritic-martensitic steels and HT-UPS austenitic stainless steels to a flowing sodium environment with controlled impurity concentrations. The exposed specimens are analyzed for their corrosion performance, microstructural changes, and tensile behavior. Previous reports examined the thermodynamic and kinetic factors involved in the purity of liquid sodium coolant for sodium reactor applications as well as the design, fabrication, and construction of a forced convection sodium loop for sodium compatibility studies of advanced materials. This report presents the results on corrosion performance, microstructure, and tensile properties of advanced ferritic-martensitic and austenitic alloys exposed to liquid sodium at 550 C for up to 2700 h and at 650 C for up to 5064 h in the forced convection sodium loop. The oxygen content of sodium was controlled by the cold-trapping method to achieve {approx}1 wppm oxygen level. Four alloys were examined, G92 in the normalized and tempered condition (H1 G92), G92 in the cold-rolled condition (H2 G92), G91 in the normalized and tempered condition, and hot-rolled HT-UPS. G91 was included as a reference to compare with advanced alloy, G92. It was found that all four alloys showed weight loss after sodium exposures at 550 and 650 C. The weight loss of the four alloys was comparable after sodium exposures at 550 C; the weight loss of ferritic-martensitic steels, G92 and G91 is more significant than that of austenitic stainless steel, HT-UPS after sodium exposures at 650 C. Sodium exposures up to 2700 h at 550 C had no significant influence on tensile properties, while sodium exposures up to 5064 h at 650 C dramatically lowered the tensile strengths of the four alloys. The ultimate tensile strength of H1 G92, H2 G92, and G91 ferritic-martensitic steels was reduced to as much as nearly half of its initial value after sodium exposures at 650 C. Though the uniform elongation was recovered to some extent, these three ferritic-martensitic steels showed considerable strain softening after sodium exposures. The yield stress of HT-UPS austenitic stainless steel increased, the ultimate tensile strength decreased, and the total elongation was reduced after sodium exposures at 650 C. The dynamic strain aging effect observed in the as-received HT-UPS specimens became less pronounced after sodium exposures at 650 C. Microstructural characterization of sodium-exposed specimens showed no appreciable surface deterioration or grain structure changes under an optical microscope, except for the H2 G92 steel, in which the martensite structure transformed to large grain ferrite after sodium exposures at 650 C. TEM observations of the sodium-exposed H2 G92 steel showed significant recrystallization after sodium exposure for 2700 h at 550 C, and transformation of martensite to ferrite and high density of precipitates in nearly dislocation-free matrix after sodium exposures at 650 C. Further microstructural analysis and evaluation of decarburization/carburization behavior is needed to understand the dramatic changes in the tensile strengths of advanced ferritic-martensitic and austenitic steels after sodium exposures at 650 C.