Crack initiation in austenitic stainless steel sanicro 25 subjected to thermomechanical fatigue

0480191 - ÚFM 2018 RIV CH eng C - Conference Paper (international conference)
Petráš, Roman - Škorík, Viktor - Polák, Jaroslav
Crack initiation in austenitic stainless steel sanicro 25 subjected to thermomechanical fatigue.
Materials Structure & Micromechanics of Fracture VIII. Zürrich: Trans Tech Publications, 2017 - (Šandera, P.), s. 273-276. Solid State Phenomena, 258. ISBN 978-3-03835-626-4. ISSN 1662-9779.
[MSMF8. International Conference on Materials Structure and Micromechanics of Fracture /8./. Brno (CZ), 27.06.2016-29.06.2016]
R&D Projects: GA MŠMT(CZ) LQ1601; GA ČR(CZ) GA13-23652S; GA MŠMT LM2015069
Institutional support: RVO:68081723
Keywords : Damage mechanism * FIB cutting * Localized oxidation-cracking * Sanicro 25 steel * Thermomechanical fatigue
OECD category: Audio engineering, reliability analysis

Thermomechanical fatigue experiments were performed with austenitic stainless Sanicro 25 steel. Several amplitudes of mechanical strain in a wide temperature interval (250-700 °C) were applied to the specimens. Mechanical response was recorded and fatigue lives were obtained. Scanning electron microscopy combined with FIB technique was used to study the mechanism of crack initiation in in-phase and in out-of-phase thermomechanical cycling. Different mechanisms of the crack initiation were found in these two types of loading. During in-phase loading fatigue cracks start in grain boundaries by cracking of the oxide. Cracks grew preferentially along grain boundaries which resulted in rapid crack initiation and low fatigue life. In out-of-phase loading multiple cracks perpendicular to the stress axis developed only after sufficiently thick oxide layer was formed and cracked in low temperature loading half-cycle. The cracks in oxide allowed localized repeated oxidation and finally also cracking. The cracks grow transgranularly and result in longer fatigue life.
Permanent Link: http://hdl.handle.net/11104/0277273