Hydrogen solubility in austenitic stainless steels

Abstract

Hydrogen volubility was directly measured in specimens of Types 304L, 21-6-9, and modified A-286 austenitic stainless steels saturated with hydrogen at 69 MPa pressure at 470 K. Nitrogen in Type 21-6-9 stainless steel and precipitate morphology in the modified Type A-286 stainless steel altered the hydrogen volubility. Cold work and surface treatment had only minor effects on hydrogen volubility in the three stainless steels.

10.2172/918137

“…The precipitation-strengthened austenitic stainless steels (A-286 and JBK-75, which are treated as a single alloy for this analysis due to the relatively small amount of data) appear to show a different solubility depending on whether the alloy is annealed or aged. In the annealed condition a "modified A-286" [28] (presumably JBK-75) was found to have a hydrogen concentration similar to 304L, while in the forged condition (and presumably aged) the alloy features a significantly lower hydrogen concentration. Our own measurements on peak aged A-286 and JBK-75 alloys (Table 7) also show a lower hydrogen concentration than measured for 304L (Table 3) and 316L (Table 4) under the same conditions.…”

“…A number of studies on austenitic stainless steels have attempted to correlate solubility with surface finish and resulting hydrogen embrittlement phenomena [27,28]. As described above, the surface condition by definition cannot affect the solubility of the lattice material, since solubility assumes thermodynamic equilibrium between the lattice and the gas phase.…”

“…Several studies on austenitic steels have shown that hydrogen transport and solubility are independent of whether the microstructure is annealed or heavily cold-worked [27][28][29], as should be expected if dislocations are weak traps and the lattice solubility is high. There are occasions, however, when hydrogen transport and solubility may appear to depend on the microstructure of the alloy.…”

“…We have taken the hydrogen concentration data reported by Caskey (Table 2) in Refs. [20,28] as well as our own data (Table 3 & 5) and used the lowest energy term (5.9 kJ mol -1 , Ref. [27]) along with the fugacity function determined in previous sections to generate solubility relationships for 304 and 21-6-9 respectively.…”

“…In Ref. [20], Caskey quotes hydrogen precharging temperature as 740 K, while plots seems to indicate that then temperature was in fact 470 K as described in another reference [28]. Table 1.…”