Fatigue Monitoring of 321 Steel Coated by Laser Additively Manufactured CoCrFeMnNi High‐Entropy Alloy Using Acoustic Emission Technique

Fatigue failure is a common mode of deterioration for steel cables (e.g., 321 stainless steel) in cable‐stayed bridges. In this case, given that the FeCoNiCrMn high‐entropy alloy (HEA) coatings have been found to simultaneously improve the fatigue and corrosion resistance of 321 steel, the fatigue crack growth behavior of 321 steel coated with selective laser melting CoCrFeMnNi HEA was further studied in this work. The results indicate that the CoCrFeMnNi alloy coating is able to increase the fatigue crack growth resistance of 321 steel by 21.43% compared to the uncoated 321 steel, and this is because the initiation of crack is mitigated by the angular disparities between adjacent grains and an increased dislocation density in the coating. Furthermore, the acoustic emission (AE) technique was used to track fatigue damage and predict fatigue crack growth life. It was found that crack length could be effectively monitored and predicted using the count and energy parameter, suggesting material and stress ratio independence in the AE technique.