MATERIAL COMPATIBILITY TESTS WITH FLOWING PB-17LI EUTECTIC

The material compatibility studies are related to the self-cooled liquid metal blanket concept. The studies are mainly concerned with the corrosion of the martensitic steel X18CrMoVNb 12 1 (MANET) in flowing liquid Pb-17Li eutectic at 500 and 550-degrees-C (773 and 823 K) in the PICOLO loop. Additional, some specimens of the austenitic steel Type 316 UN) and of the loop material, the ferritic steel X10CrAl 7, were exposed to the eutectic alloy, the flow velocity of which was maintained at 0.3 m/s. The temperature gradient in the two tests series was 240 and 190 K, respectively. The specimens were corroded by the flowing liquid alloy by means of the removal of material from their surfaces. The material loss generally reaches a region of linear rates after an initial period of slower corrosion rates. It is shown that the linear rates for iron rich materials are in good agreement with rates calculated on the basis of an hydraulic model for turbulent flow conditions. The faster corrosion of the austenitic steel is due to the selective leaching of Ni and Mn out of surface layers which change their structure into the alpha-Fe type and get a large number of cavities. The initial period of slower corrosion seems to be related to the composition of the material. At lower Cr contents, the initial period becomes very short or disappears completely. This indicates an influence of the stability of passivation layers on the inhibition of the Pb-17Li corrosion of steels.