Document Type : Research Article

Authors

• S. C. S. P. Kumar Krovvidi
• G. Padmakumar
• A. K. Bhaduri

Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu, 603102, India

Abstract

Bellows find wide applications in reactor systems such as in bellows sealed valves as primary leak tight barriers and in piping systems to absorb differential thermal expansions. Reliable operation of bellows is strongly dependent of proper material selection. Various candidates for material of the bellows are austenitic stainless steels (such as SS316, SS304, SS316Ti, SS304L etc.), precipitation hardened stainless steels (such as AM350) and Nickel base alloys such as Inconel-718 and Inconel-625. This paper presents the review of the operating experience, mechanical & neutronic properties of various materials for bellows in nuclear industry. In this work, it is observed that Inconel alloys have superior mechanical properties than austenitic stainless steels but exhibit neutron embrittlement. Hence, use of Inconel bellows is limited to low neutron fluence applications. Precipitation hardened steels such as AM350 have high mechanical strength but lesser ductility. Though AM350 is not suitable for formed bellows, it has excellent operating experience for welded disc bellows in nuclear applications. Austenitic stainless steels have large operating experience. Variants of SS316 are used for high temperature and variants of SS304 are used for temperatures below creep range. ‘L’ grades or stabilized grades are used for resistance to sensitization during welding. Based on the present review work, guidelines for selection of material for bellows are drawn, satisfying the selection criterion. Copyright © 2017 VBRI Press.

Keywords

• Material of construction of bellows
• austenitic stainless steels
• Inconel 718
• Inconel 625
• AM350