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A fatigue and creep study in austenitic stainless steel 316L used in exhaust pipes of naval gas turbines
Author(s) -
MARTINS R. F.,
BRANCO C. M.
Publication year - 2004
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.2004.00783.x
Subject(s) - creep , materials science , welding , metallurgy , microstructure , austenitic stainless steel , butt welding , composite material , carbide , tube (container) , corrosion
Exhaust pipes of naval gas turbines are made of thin wall tubing of stainless steel grade AISI 316L. The tubes are fabricated by butt welding of different sections with longitudinal and circumferential joints. The plate thickness is about 4.0 mm, and the working temperature varies between 600 °C and 400 °C in the critical zones of the pipe, in the lower and central areas, respectively. The loadings in the tube induce high‐temperature fatigue and creep‐fatigue cracks have nucleated and propagated in the tube near some welded joints. The paper presents FCGR data obtained in CT specimens of used material taken from the pipes and tested at RT, 335, 500 and 600 °C. Preliminary creep data obtained in tension, in thin‐sheet specimens (about 4 mm thickness), also taken from the conduct wall and tested at 500, 550 and 600 °C are also given. These results are crucial to perform a fatigue‐creep interaction life assessment of the critical parts of the structure in the near future. Finally, the paper presents results of research work to investigate carbide precipitation and formation in virgin thin‐sheet specimens subjected to several types of thermal exposures. In some cases, 3–4 d was the time interval between exposures. Grain size measurements were carried out together with microstructural observations in the SEM. The influence of time, temperature and time interval between thermal exposures was assessed comparing the microstructures.