Improved creep‐fatigue and remnant tensile/creep properties of 321 stainless steel by self‐healing coating

Abstract

AbstractAISI 321 steels used as intake valves in turbines are frequently subjected to creep‐fatigue (C‐F) exposure during service. Improving C‐F resistance and assessing remnant creep/tensile properties are therefore required for their safe service. In this work, the self‐healing coating consisting of Al2O3‐13TiO2 layer, TiC layer, and NiCrAlY layer was prepared for 321 steel. The effects of such self‐healing coating on the C‐F and remnant creep/tensile properties were studied. The results showed that the initial hardening phenomena of the studied steel during C‐F exposure was mainly attributed to the dislocation strengthening and a certain level of carbides precipitation strengthening, while the subsequent softening behaviors were resulted from dynamic recovery and coarsening of carbides. Moreover, as compared to other coatings, the self‐healing coating is able to improve the mechanical properties of steels due to dislocation strengthening, precipitation strengthening, and the self‐healing behavior resulting from the reaction between the TiC layer and oxygen.