Fatigue Behaviour of 316 Grade Austenitic Stainless Steel Pipes at Elevated Temperature

摘要

This paper presents results of a fatigue crack growth study carried out in CT specimens of 3.6mm thickness of base metal 316 grade austenitic stainless steel, material taken from service pipes and tested at room temperature, 335 and 500 ℃ for a stress ratio of R ≈0.1, under a constant amplitude sinusoidal load wave with a frequency between 10 and 15 Hz. Both da/dN;ΔK and threshold data were obtained and compared at these temperatures. Results of optical microscopy for the microstructure of the material and analysis of the fracture surfaces carried out with the SEM have identified the failure mechanisms operating at these temperatures. A discussion is presented concerning the determination of the threshold ΔK_0. The FCGR results have shown a significant increase of da/dN with temperature, and a corresponding lowering of ΔK_0. The present results cannot be compared directly with data available in the literature for virgin exposed 316 plate.