Effect of Lead and Lead–Bismuth Eutectic Melts on the Fatigue Life of Steels of the Martensitic and Austenitic Classes

Abstract

We study the effect of lead and lead-bismuth eutectic melts on the fatigue properties of martensitic Fe-13Cr and austenitic Fe-18Cr-10Ni steels within the temperature range 200-450°С. It is shown that the liquid-metal medium contributes to a significant decrease in the fatigue life of steels and the action of eutectic melt is more negative. The fatigue properties of austenitic Fe-18Cr-10Ni steel undergo weaker changes under the influence of lead and lead-bismuth eutectic melts. The realization of the projects of nuclear power plants of new generation requires the solution of a series of materials-science problems dealing with the development of reactor materials (1−4). It is supposed that steels of the austenitic and ferritic-martensitic classes may serve as the main structural materials of nuclear power plants. Despite the well-known susceptibility of steels of the austenitic class (based on the Fe−Cr−Ni system) to the de- velopment of vacancy porosity in the course of their high-temperature neutron irradiation, it is proposed to make the vessel of a BREST-type fast-neutron reactor and some in-vessel workpieces of chromium-nickel steel, which does not require additional thermal treatment after welding (5). Steels of the ferritic-martensitic class (based on the Fe−Cr system), due to their high thermal and mechanical characteristics, compatibility with the main cooling media, and lower sensitivity to swelling as compared with steels of the austenitic class, remain promising mate- rials for the first wall and blanket of fusion reactors, as well as for fuel elements, steam generators, and structural elements of the coolant pumps in the fast-neutron reactors (6, 7). The melts of heavy metals (Рb, Ві, and their eutectic mixture Pb−Bi), due to their nuclear and thermal prop- erties are regarded as promising cooling media for fast-neutron reactors (of the BREST-, SVBR-, and MBIR- types) and also for the subcritical hybrid systems controlled by accelerators (8−10). The problem of corrosion activity of these media in contact with steels is solved by using lead coolants with controlled oxygen contents, which promotes the formation of protective oxide films on the steel surface (11). Another hazard encountered in the course of operation of nuclear power plants is connected with liquid-metal embrittlement, which manifests itself in the degradation of the mechanical properties of structural materials in the course of their interaction with the melts of heavy metals. Unlike the studies of corrosion processes, the investigations of the influence of liq- uid-metal media on the degradation of the mechanical properties of steels are not systematic. This fact compli- cates the analysis of the mechanisms of crack initiation and propagation and the character of failures depending on the media and operating temperature and does not enable one to predict various manifestations of the interac- tions between liquid and solid metals and, hence, to predict the behavior of structural materials. Therefore, the analysis of the scientific aspects of the effect of lead melts (Рb, Рb−Bi) on the mechanical properties of steels of