Experimental and numerical assessment of thermal fatigue in 316 austenitic steel pipes

This paper presents an experimental and numerical investigation of thermal fatigue of 316L steel pipe components with 14 mm wall thickness heated by induction to 300–550 °C on the outer surface and cyclically cooled internally with room temperature water. The damage is initiated as network of surface cracks where some cracks become dominant. At 550 °C the pipe fails after typically 50,000 cycles whereas at 300 °C the deepest cracks have only penetrated half the thickness after 250,000 cycles. By applying a small axial load the deepest cracks switch from axial direction to circumferential. An elasto-plastic fatigue model was adopted to simulate the crack propagation. The difference in crack propagation rate and fatigue life when the temperature is increased is well captured by the model, but the agreement with tests depends on the applied fatigue crack growth parameters.