Creep deformation characteristics of austenitic stainless steel foils

Abstract

Creep deformation process of austenitic stainless steel foil with thickness 0.25 mm was investigated. The foil specimen was creep tested at 750oC, 54 MPa to establish baseline behavior for its extended use as primary surface recuperator in advanced microturbine. The creep curve of the foil shows that the primary creep stage is brief and creep life is dominated by tertiary creep deformation. The curve is well represented by the modified theta-projection concept model with hardening and softening terms. Morphology of fractured foil surface reveals intergranular fracture with shallow network of faceted voids. The formation of w-type creep cavities is significant, as revealed by microstructure of ruptured specimen. Composition analysis indicates the formation of carbides, namely, Cr23C6, NbC and Fe3Nb3C.