In-sodium tests of hard facing materials (III)

Hasegawa, Naruo; Kano, Shigeki; Nakayama, Koichi; Koakutsu, Toru; not registered; Nakasuji, Takashi

Friction, wear and self-welding resistant materials are applied for many contact and/or sliding parts in FBR components. The pad material of a fuel assembly wrapper tube is a ypical example. Wrapper tube pads of "MONJU" size were trially manufactured with four kinds of hard facing material selected by up to date R&D tests ((1)Stellite No.6 (2)Colmonoy No.6, (3)LC-1C (Chromium Carbide), (4)Inconel 718). In this study, these pads were exposed to 600C sodium for 2,000 hrs.. The following results were obtained. (1)The dimension between the inside of wrapper tube and the pad surface partially changed max. 200m due to the heating during sodium exposure. (2)Stellite No.6: After exposure, the surface showed general corrosion and selective corrosion at the grain boundary. The hardness slightly decreased to Hv 600 and surface roughness slightly increased. (3)Colmonoy No.6: After exposure, the surface showed severe general corrosion, then the depletion of boron and silicon and the degraded layer were observed in the vicinity of the exposed surface. The hardness of this layer significantly decreased to Hv 300 and the surface roughness slightly in creased. (4)LC-1C: After exposure, the surface showed slight general corrosion but cross-sectional micrograph was stable. The hardness increased to Hv 1,100 and the surface roughness slightly increased. (5)Inconel 718 : After exposure, the surface corrosion was slight, but titanium, niobium and molybdenum were depleted in the vicinity of the expoded surface. The hardness and surface roughness did not change before and after exposure.