Corrosion Fatigue Crack Growth Behavior of 13Cr-L80 Steel for High-Production Gas Well Tubing

Compact tensile specimens taken from 13Cr-L80 steel tubing were pre-corroded with composite phosphate completion fluid, and then was subjected to fatigue crack growth tests. By analyzing morphology of the fatigue crack growth zone, the effects of stress ratio (0.05-0.25), load (10-14 kN) and load frequency (0.6-1.8 Hz) on the corrosion fatigue crack growth behavior were studied. The results show that with increasing stress ratio, the number of secondary cracks in the fatigue crack growth zone increased, and the crack growth rate of 13Cr-L80 steel was improved. With increasing load, the number of secondary cracks in the fatigue crack growth zone decreased, and the crack growth rate was reduced. The higher the load frequency, the smaller the number of secondary cracks in the fatigue crack growth zone; but the strain rate at crack tips increased, and the crack tip deformation was more sufficient, leading to the fast crack growth, and the smaller number of cycles at test termination.