全肉厚試験片によるNi基合金製溶接配管のクリープ破壊挙動および非破壊損傷検査法の適用

抄録

Creep rupture behavior of HR6W weldment using full thickness specimen cut from the circumferentially welded pipe was investigated for evaluating its applicability to advanced USC (A-USC) power plant. Creep tests were conducted at 750°C for durations up to 8,600 hours, and damage morphology of weldment during creep was characterized. The applicability of several nondestructive detection methods to the creep damage evaluation was discussed. It was found that full thickness specimen was broken at the base metal and main crack was inclined approximately at 45 degrees to the axial direction of the specimen. Based on stress at the ruptured location, times to creep rupture of full thickness specimen were comparable with those of the smooth bar specimen of base metal. Among several nondestructive detection methods, a small crack in base metal on the outer surface was first observed at life fraction of 35% by replication. PT can detect the crack up to 0.5mm in length in about half of the life. The crack whose length is longer than 3mm can be detected by UT in latter half of the life.