Overview of Intergranular Fracture of Neutron Irradiated Austenitic Stainless Steels

Abstract

Austenitic stainless steels are normally ductile and exhibit deep dimples on fracture surfaces. These steels can, however, exhibit brittle intergranular fracture under some circumstances. The occurrence of intergranular fracture in the irradiated steels is briefly reviewed based on limited literature data. The data are sorted according to the irradiation temperature. Intergranular fracture may occur in association with a high irradiation temperature and void swelling. At low irradiation temperature, the steels can exhibit intergranular fracture at low or even at room temperatures during loading in air and in high temperature water (~300 • C). This paper deals with the similarities and differences for IG fractures and discusses the mechanisms involved. The intergranular fracture occurrence at low temperatures might be correlated with decohesion or twinning and strain martensite transformation in local narrow areas around grain boundaries. The possibility of a ductile-to-brittle transition is also discussed. In case of void swelling higher than 3%, quasi-cleavage at low temperature might be expected as a consequence of ductile-to-brittle fracture changes with temperature. Any existence of the change in fracture behavior in the steels of present thermal reactor internals with increasing irradiation dose should be clearly proven or disproven. Further studies to clarify the mechanism are recommended.

Elastic Properties of FeCr20Ni8Xn (X = Mo, Nb, Ta, Ti, V, W and Zr) Austenitic Stainless Steels: A First Principles Study

“…Austenitic stainless steels are widely used in the nuclear, oil and chemical industries, owing to their excellent mechanical properties, weldability and corrosion-resistance properties [1][2][3][4]. However, when exposed to elevated temperature (500-800 • C), these alloys become susceptible to intergranular corrosion and stress-corrosion cracking.…”

Study on in-Service Inspection Program and Method for Fuel Handling System of Rde

“…There are a few research have been conducted to investigate the effects of environmental operation which may promote the degradation and aging mechanism of metals structure in high-temperature gas reactors (HTGR) components [1][2][3][4][5][6]. One of the previous research proposed that the effects of high-temperature helium with gas impurities may cause stress corrosion to crack initiation and growth rate, crevice corrosion crack initiation and growth rate, and cyclic crack growth rate [6].…”

“…One of the previous research proposed that the effects of high-temperature helium with gas impurities may cause stress corrosion to crack initiation and growth rate, crevice corrosion crack initiation and growth rate, and cyclic crack growth rate [6]. Due to the helium behavior is insoluble in metal, the gas molecule tends to precipitate as clusters and nanometer-scale bubbles even at relatively low temperatures [5]. These bubbles have been suspected to promote the void formation in the micro-grain boundary and initiate the crack.…”

Improving the Reliability of Mechanical Components That Have Failed in the Field Due to Repetitive Stress

“…By utilizing the above failure analysis (and tests), fractures that started in voids inside mechanical parts such as gear have been shown to propagate to their ends [23][24][25][26][27][28][29][30]. In particular, intergranular fractures of austenitic stainless steels have been identified and discussed in a similar way to the failure of the helix dispenser [31]. A phase field visco-plastic model has also been proposed to describe the influence of the loading rate on the ductile fracture [32].…”