Fundamental Study on Fretting Corrosion in Solid Breeder Blanket

Abstract

Lithium titanate (Li2TiO3) is candidate tritium breeder of the fusion blanket systems. The small pebbles of Li2TiO3are packed in the blanket box. The coolant tubes made of RAFM steel F82H (Fe-8Cr-2W-0.1C) are installed in the blanket box and their oscillation is possibly induced by the coolant flow. The fretting corrosion is then caused by the reciprocating slip of the pebbles on the tube wall. The purpose of the present study is to investigate the fundamental behaviors of fretting corrosion between Li2TiO3pebble and the F82H plate. The small pebble of Li2TiO3or Al2O3was placed on the plate specimen of F82H in point contact, and the plate specimen was oscillated horizontally and lineally at the frequency of 50Hz and the amplitude of 120 μm. The constant load of 4.9 N was applied between the small pebble and the plate specimen. The fretting tests were conducted for 10 and 300 minutes in an air atmosphere at a room temperature. The Li2TiO3pebble was significantly abraded in the tests. The surface of the F82H specimen was damaged due to the scratch with the broken particles of the pebble. The fretting corrosion of F82H was promoted in the test with Al2O3pebble, since the formation and destruction of the oxide layer were repeated on the steel surface in the fretting cycle.