Stress corrosion cracking of ferritic-maretensitic steels in simulated boiling water reactor environment

Abstract

Stress corrosion cracking of APMT (Advanced Powder Metallurgy Technology) and T91 (ferritic-martensitic) steels were investigated in the as-received and proton-irradiated conditions in simulated boiling water reactor environment (2 ppm O 2 ) using constant extension tensile tests at 288°C at a strain rate of 3×10 -7 s -1 . Significant stress corrosion cracking was not observed in the as-received condition. A few cracks, perpendicular the loading direction, were observed in the proton-irradiated (5 dpa) specimen of T91. No intergranular fracture was observed on the fracture surfaces of as-received and proton-irradiated specimens of T91. No cracking was observed for APMT in un-irradiated and proton-irradiated (5 dpa) conditions. Results indicate that both APMT and T91 are highly resistant to stress corrosion cracking in a reactor environment and that irradiation to 5 dpa does not appreciably increase susceptibility.

Mechanical properties of neutron-irradiated model and commercial FeCrAl alloys

“…The alloy exhibited the highest degree of uniform plastic deformation of any alloy tested when it was tested at high temperature. Furthermore, it showed signs of dynamic strain aging, a result consistent with previous findings for different heats of Kanthal APMT [14,23,24]. Fracture surfaces in the specimens tested at room temperature showed trademark transgranular fracture with faceted textures and river markings ( Figure 2c).…”

“…Retained ductility has direct implications in the performance of cladding under operation especially when subjected to pellet-cladding mechanical interaction. The similar mechanical performance, especially in relation to ductility, between both alloy classes, the retained deformability in the lower Cr FeCrAl alloys indicated by the reduction-of-area results in Figure 8, and limited susceptibly of FeCrAl alloys to corrosion-assisted embrittlement [14,38,39] suggests the applicability of FeCrAl alloys as ATF LWR cladding from the standpoint of tensile properties under irradiation. Other mechanical properties, such as thermal creep and irradiation creep, should be determined prior to conclusively determining commercial use of any FeCrAl alloy as ATF LWR cladding.…”

“…Building on this, Field et al conducted mechanical tests on neutron-irradiated model FeCrAl alloys of varying compositions to 1.8 dpa at 382°C, which showed similar behavior with significant hardening and a composition dependence in the hardening driven by the formation of the Cr-rich α' phase [13]. Additional work has been completed on commercial alloys, such as the study of Ahmedabadi and Was in which the Kanthal Advanced Power Metallurgy Technology (APMT) alloy was proton-irradiated to 5 dpa at 360°C and tested using constant-extension-rate tensile tests; it demonstrated good stress corrosion cracking resistance and reduction of area [14]. Other than these studies, few details exist for the mechanical response of neutron-or ion-irradiated FeCrAl alloys.…”

Iron-chrome-aluminum alloy cladding for increasing safety in nuclear power plants

“…Because of its ferritic or bcc structure, FeCrAl alloys are also more resistant to irradiation degradation than prior versions of austenitic SS cladding materials. Proton irradiation studies performed at the U. of Michigan showed that FeCrAl materials may be resistant to proton irradiation induced cracking providing additional confirmation of the potential acceptability of FeCrAl materials for fuel rod cladding [12]. Although there may be nominal changes in fuel rod geometry (e.g.…”

Handbook of the Materials Properties of FeCrAl Alloys For Nuclear Power Production Applications

“…For high-Cr ferritic steels, including FeCrAl alloys, limited studies have been completed. Currently, the only known work on SCC of FeCrAl alloys has been completed on Kanthal APMT by Andresen et al/Rebak [84,85] and by Ahmedabadi and Was [86]. The study of Ahmedabadi and…”