Failure analysis of an AM 350 steel bellows

Abstract The failure of an AM 350 steel bellows, which was to be used in the control rod drive mechanism (CRDM) of the fast breeder test reactor (FBTR), was noticed during helium leak testing. The leak test was carried out before performance testing in a test rig. Visual examination of the leak area did not indicate any obvious defect. Stereo microscopy and optical microscopy indicated the presence of pits. A few of these pits had propagated through the thickness. EDAX of the corrosion products revealed the presence of chlorides. The exposure of the bellows to a marine atmosphere during a storage period of 13 years was suspected to have caused the pitting.