Effects of sodium and lithium environments on mechanical properties of ferrous alloys

Evaluation of the Effect of Dynamic Sodium on the Low Cycle Fatigue Properties of 316L(N) Stainless Steel Base and Weld Joints

“…The data ob- tained in this investigation agrees well with that of the results reported on AISI 304 stainless steel [14][15][16] and AISI 316 stainless steel [14,[17][18][19]21]. The generally accepted reason for increase in life in sodium environment when compared to air environment is the lack of oxidation effects in high purity sodium [24]. Liquid metals can influence the surface-active properties of the material through Liquid Metal Embrittlement (LME), oxidation, nitridation, or carburization -decarburization phenomena, all of which can alter near-surface deformation behaviour and thus alter mechanical properties such as fatigue crack initiation and propagation.…”

“…It has been postulated [12] that the decrease in crack propagation is due to lack of oxidation of the newly created crack surfaces during the tensile part of the cycle and partial rewelding during the compression part of the cycle. On the other hand, it has been suggested [24] that crack growth occurs from two sources, one being mechanical and the other being oxygen penetration at the crack tip; obviously in high purity, low oxygen sodium there will be virtually no contribution from the second source and hence the crack growth rate will be lower.…”

“…Liquid metals can influence the surface-active properties of the material through Liquid Metal Embrittlement (LME), oxidation, nitridation, or carburization -decarburization phenomena, all of which can alter near-surface deformation behaviour and thus alter mechanical properties such as fatigue crack initiation and propagation. An increase in the carbon concentration on 316 stainless steel has no significant effect on strength and ductility of the material and hence is unlikely to affect the fatigue behaviour [24].…”

Effect of sodium environment on the low cycle fatigue properties of modified 9Cr–1Mo ferritic martensitic steel

“…7(b)) shows substantial oxidation that may influence cyclic deformation in several ways. Oxidation of the slip steps can prevent slip reversal, segregation of nonmetallic elements at grain boundaries or slip bands may accelerate cracking and strengthening of the surface due to oxide film that can cause strain accumulation and enhanced cavitation all of which can alter near-surface deformation behaviour and thus alter mechanical properties such as fatigue crack initiation and propagation [25]. The analysis on the longitudinal cut specimens reveal that the sodium tested samples are free from secondary cracks in contrast to the air tested samples with a numerous secondary cracks (Fig.…”

Low cycle fatigue properties of modified 9Cr-1Mo ferritic martensitic steel weld joints in sodium environment

“…Data indicate that LME does not occur in sodium environment [26]. Other processes that may alter mechanical properties depend on the purity of the environment, i.e., the chemical activity of oxygen, nitrogen, carbon etc., in the liquid metal.…”