Probability Approach for Prediction of Pitting Corrosion Fatigue Life of Custom 450 Steel

In this study, the pitting type of corrosion growth characteristics, fatigue crack initiation and propagation behavior; axial fatigue tests were carried out on precipitation hardened martensitic Custom 450 steel in the air and 3.5wt% NaCl solution. Using the ratio of the depth to the half-width of the pits; (a/c)= 1.5±0.2 the corrosion pit depth growth law was obtained as a function of stress amplitude and elapsed time, t. Fatigue crack growth rates were determined in the near threshold stress intensity factors regime (∆kth). A model was presented for estimation of corrosion fatigue life based on the time to reach critical pit depth (as crack initiation) and crack propagation life. Then. S-N curves were obtained both in air and NaCl solution from axial fatigue testing. Comparison of data from the proposed model and the experimental results (S-N curves) showed good agreement.