Effect of dissolved oxygen concentration on dynamic strain aging and stress corrosion cracking of SUS304 stainless steel under high temperature pressurized water

Under high temperature pressurized water assuming the interior of a typical nuclear reactor, dynamic strain aging (DSA) and intergranular stress corrosion cracking (intragranular SCC) occur due to changes in dissolved oxygen (DO) content, respectively. In order to clearly understand the difference between these phenomena, the mechanism of their occurrence was summarized. As a result, DSA due to intragranular cracking was found to occur in AISI 304 stainless steel at low DO < 1 ppb and 100 ppb, while DSA was suppressed at DO 8500 ppb due to the formation of oxide films on the surface. On the other hand, when DO was increased to 20000 ppb, the film was peeled from the matrix, O element diffused to the grain boundary of the matrix, resulting in intergranular SCC. These results are indicated that the optimum DO concentration should be adjusted to suppress crack initiation due to DSA and intergranular SCC.