The pre-corrosion fatigue behavior of 321 steel coated by laser additively manufactured FeCoNiCrMn high-entropy alloy

Abstract

Corrosion caused by salt-spray and fatigue failure resulting from cyclic sea wave and strong storm are common degradation problem in offshore structural steels, and their interaction would accelerate service failure of these steels. In this work, therefore, FeCoNiCrMn high-entropy alloy (HEA) coatings were first prepared on 321 steels to simultaneously improve their corrosion and fatigue resistance. Then the pre-corrosion in salt-spray environment and subsequent high-cycle fatigue (HCF) tests were conducted on both coated and uncoated steel. The same HCF tests were also performed on the uncorroded steel specimens to reveal the influence of pre-corrosion on their fatigue resistance. The results showed that the corrosion and fatigue resistance of coated steel were both improved, which should be attributed to the higher strength, dislocation motivity and formation rate of corrosion film of the HEA coating. Moreover, pre-corrosion would decrease the mechanical properties and depth of the HEA coating, leading to significant damage to the fatigue resistance of coated steel. However, after pre-corrosion, the fatigue life of uncoated and coated steel was decreased by 18.2 %–38.8 % and 34.4 %–42.6 % at different stress amplitudes, respectively, showing the significant protective effect of HEA coatings against the pre-corrosion damage to fatigue life of offshore 321 steel.