Prediction Method of Corrosion Fatigue Crack Initiation Life Based on Corrosion Pit Growth Mechanism

Abstract

Corrosion fatigue crack initiation behavior of low alloy steel has been investigated in water It was observed that corrosion fatigue process was composed of three stages, namely, corrosion pit growth, transition into crack from the corrosion pit and corrosion fatigue crack propagation. The corrosion pit size was found to increase with time t following the relation: corrosion pit size ∝ t1/3. The condition of transition into crack from the corrosion pit was determined by a stress intensity factor J3y assuming the corrosion pit as a sharp crack. The critical pit condition (ΔK)P was 1.2 MPa √m for 2.5 NiCrMoV and 3.5 NiCrMoV in 90°C water with 100 ppb dissolved oxygen. Based on the abovementioned results, residual life prediction method for corrosion fatigue crack initiation was proposed. © 1987, The Japan Society of Mechanical Engineers. All rights reserved.