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Kano, Shigeki; Koakutsu, Toru; Hasegawa, Naruo; Nakayama, Koichi; Nakasuji, Takashi; Atsumo, Hideo

A corrosion test of hard facing material has been conducted in 600C sodium for 2000 hrs. Test pieces were Co base alloys, Ni base alloys and carbides which were provided for tribology studies in sodium. These materials were compared with SUS304, SUS316 and another corrosion and heat resisting alloys by simultaneous exposure. Analysis methods after exposure were as follows: surface roughness, hardness, corrosion rate, surface morphology and metallurgical structure which have influence on friction and self-welding behavior. The results obtained are as follows: (1)Stellitew alloys: Part of test pieces showed weight gain. Change of surface roughness was minute. Structural change was not observed in the surface vicinity of sodium contact. However, hardness increase was observed. (2)Ni base hard facing materials such as Colmonoy alloys: Corrosion rates were high and hardness was reduced. A degraded layer of 10m through 40m was observed on the surface of Colmonoy alloys and their surface roughness increased. (3)Inconel alloys: Corrosion rates were double those of stainless steels. A degraded layer of 1m through 4m was observed on the surface. Change in surface roughness was minute. (4)Corrosion and heat resisting alloys: Corrosion rates showed one to two times greater than those of stainless steels. Change in surface roughness was minute. No change in surface layer was observed. However, precipitates were observed in the metallurgical structures of some alloy types. (5)Carbides: Large increase of surface roughness was observed. LC-1C exhibited stripping from substratum. LW-1N40 indicated wide variation in corrosion rates. (6)Other materials: SUS316 produced a sigma phase at the grain boundary of sodium surface contact.