850℃에서 Alloy 800H 모재와 용접부재의 저사이클 피로 특성

Abstract

Alloy 800H is one of the candidate materials for key structural components such as control rod systems, hot gas duct, core barrels, core supports, and a shut-down cooling systems for the very high temperature reactor systems. The start-up and shut-down and power transmission of the reactors cause low cycle fatigue (LCF) and creep fatigue (C-F). The research results of many scholars have been published in the literature on the characterization of low cycle fatigue properties of Alloy 800H. However, the results on the low cycle behavior of Alloy 800H weldments are still very few. Therefore, it is valuable to study the low cycle fatigue properties of Alloy 800H at high temperature. The aim of this study is to compare the low cycle fatigue behaviors of Alloy 800H Base metal and weldments at 850℃. Low cycle fatigue test were carried out by four different total strain ranges of 0.6%, 0.9%, 1.2% and 1.5% under a series of fully reversed strain-controls and at constant strain rate of 10-3/s. In all test conditions, the fatigue life of base metal and weldments were decreased with increasing the total strain range. And the cyclic stress response behavior showed cyclic softening phenomenon for both two materials. Finally, the low cycle fatigue morphologies were by using SEM(scanning electron microscope) and OM (optical microscope). The fracture surface of the Alloy 800H base metal and weldments started in the form of transgranular and was propagated to the final fracture.