Abstract: 15Mo3 type steel samples were subjected to creep loading at 550°C in order to
investigate the development of microstructure as well as the effect of the carbides. It was found that after reaching the secondary creep region, the slope of the creep curve decreased, the creep rate reached a minimum value and remained unchanged as the effect of strainhardening is counterbalanced by an annealing influence. After a short plateau, the slope increased. In order to explain this type of behaviour and to suggest a damage mechanism, TEM and EBSD investigations were performed. At the beginning of the process, subgrain formation started which was retarded by the carbides. At elevated temperature, however, the average distance between carbides increased, and the pinned dislocations were able to bypass them, the internal strain inside the grains (after reaching a maximum value after about 481 hours) decreased, and the creep process accelerated.
Abstract: Structural integrity of the reactor pressure vessel of pressurized water reactors is
one of the key safety issues in nuclear power operation. Integrity may be jeopardized during operational transients. The problem is compounded by radiation damage of the vessel structural materials. Structural integrity assessment as an interdisciplinary field is primarily based on materials science and fracture mechanics. The paper gives an overview on the service induced damage processes and associated changes of mechanical properties, the prediction of degradation and the assessment of the entire component against brittle fracture
with a special focus on how the evolution of materials science and engineering has
contributed to reactor vessel structural integrity assessment.
Abstract: In the present paper the secondary emission and work function of W covered with different thickness Ba layers are compared. The secondary emission and work function were measured by Work Function Spectroscopy (WFS). It is clearly pointed out that the thin Ba coating causes the the enhancement of electron induced secondary electron emission. In high pressure discharge lamps high secondary emission and high thermionic current are required for reliable operating conditions,
i.e., for reaching the nominal burning voltage and current etc. The results prove that the Ba spreading on the W surface from an alkali earth tungstate material is advantageous for lowering the work function and, simultaneously, for increasing the secondary emission yield.
Abstract: A new “Closely Packed Equal Sphere” (CPES) infiltration model has been developed by us. It differs from the classical capillary infiltration model mainly in the value of the critical contact angle of spontaneous infiltration (50,7o, instead of 90o), and as a consequence, it also differs in the functional relationship between the threshold pressure and the contact angle. Our new equation becomes identical with the Carman equation for perfectly wettability. Our experimental results are
in good agreement with these theoretical results.
Abstract: The aim of this paper is to review all the existing literature models on the concentration dependence of the viscosity of binary liquid alloys and to check them against the measured viscosity values in the binary liquid Cu-Ag system at 1373K.