Remnant tensile and creep properties of aluminized AISI 321 austenite stainless steel under prior creep–fatigue interaction

Aluminized AISI 321 steels applied as heat exchange tube are generally subjected to creep–fatigue (C‐F) exposure during service. Remaining tensile and creep performance of this steel at 620°C were therefore studied under prior C‐F deformation. Results revealed that residual properties exhibit an initial increase and followed degradation with rising lifetime fraction of prior C‐F. The tensile strength and creep lifespan reach highest at 30% lifetime fraction, since dislocation cell networks are well developed and secondary nanotwins are activated at substrate. Additionally, dynamic recovery and wavy slips occurred in coatings partially accommodate local plastic deformations and inhibit defect initiations, avoiding premature material fracture. On the other hand, these networks could restrain the increase in coating thicknesses. When the lifetime fraction of prior C‐F increases to 80%, declined remnant properties are observed, which is attributed to the recovery of dislocation cells and carbide coarsening. Meanwhile, coating microcracks also accelerate steel failure.