Experimental insight on the fatigue resistance of FV520B-I stainless steel under corrosive environments

Corrosion fatigue is the main concern for FV520B-I steels in broad industries. However, the corrosion fatigue behavior has not been elucidated clearly. In this paper, the designed corrosion fatigue tests in air, water, 3.5% and 5% NaCl solution are carried out. It is found that with the transformation of test environments from the air to NaCl solution, the fatigue life decreases from VHCF to HCF; and in the water, it spans two ranges. With the comprehensive combination of test data and the Basquin formula, the fatigue S-N formula in the different environments are achieved, the undetermined formula parameters for different test environments have been estimated, which can reflect the influence of different corrosive mediums on the fatigue resistance. The observations of post-mortem specimens clearly show that, in the water, both the internal failure and surface failure are detected when the fatigue life reaches VHCF regime, and with the fatigue life decreases to HCF regime, the fatigue failure is mainly from the surface. While, in the NaCl solution, and corrosion fatigue failure only tends to originate from the surface crack, obvious corrosion traces are observed around the region of crack initiation sites.