DESTRUCTIVE AND NON-DESTRUCTIVE TECHNIQUES APPLIED TO THE CHARACTERIZATION OF AS-CAST MODEL STEELS WITH PARAMETRIC VARIATION OF Ni, Mn, Si AND Cr CONTENT

Abstract

The present work is aimed to investigate the role and influence of certain elements as Cr, Ni, Mn and Si on the radiation stability of reactor pressure vessel steels. The 12 ferritic steels with basic typical composition of WWER-1000 and PWR reactor pressure vessel materials were manufactured and submitted to Charpy impact, Barkausen Noise, Vickers hardness and SEM testing. Results of Charpy impact test show, that DBTT (ductile-to-brittle transition temperature) values are independent on the tested steels composition and are ranging between -150 and -104 C. Only two steels show extremely high DBTT (-16 and -42 C ); the mentioned steels contain low concentration of Ni and high concentration of Cr and vice versa. For those materials an additional heat treatment is designed in order to increase the DBTT values to values more near to those of the other steels. The results of MBN measurements show that the amount of Cr plays an important role: an increase of Cr content in model steels leads to an increase of RMS (root means square) values independently on Mn and Si contents. The percentage of Ni has also significant influence i.e. low Ni content is responsible for lower RMS values. By comparing the HV10, RMS and DBTT values of the 12 model steels it is not possible to find a general conclusion. However, most of the model steels combine high values of RMS with low values of DBTT. The next step will be the neutron irradiation of such model steels in the HFR-LYRA irradiation facility up to accumulated neutron fluence in the order of 1019 n.cm-2 and the further comparison of material properties before and after irradiation.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen