Creep studies of Cold Worked Austenitic Stainless Steel

Abstract

Ti modified 14Cr-15Ni austenitic stainless steel (SS) has been developed for nuclear fuel cladding and wrapper material for its superior creep strength and better void swelling resistance during service. Cold working induces high dislocation density network in the material. These dislocations interact with point defects, which are generated by neutron irradiation during service and facilitate recombination to make the material more void swelling resistant. In present investigation, creep behavior of various cold worked (up to 40%) samples in comparison with mill annealed samples was studied. Initially, the steel was solution treated at 1333 K for 30 minutes followed by cold rolling at room temperature. Uniaxial creep test was performed at 973 K for 200 MPa stress level. The effects of cold work as well as stress on creep behavior have been studied in this investigation. Cold worked samples exhibited better creep strength as compared to mill annealed samples. During creep exposure at 973 K, material showed phenomena of recovery as well as recrystallization due to initial cold working. This partial recovery and recrystallization in material also depend upon the applied stress and led to variation in creep strength of the material. Precipitation of carbides particles was seen to be accelerated at the grain boundaries and this phenomenon was more prominently observed in cold worked samples.