In-sodium tests of hard facing materials (VI); Temperature dependence of self-welding characteristics by tension breakaway

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

It is requested to obtain the self-welding characteristics in sodium on the contacting materials of "MONJU" components. By tension breakaway method, the tests were up to date conducted on many kinds of materials in sodium which was not cold-trapped and was purified by the cold trap temperature of 190C or 145C. These results were used for material screening. The present study relates to the dwell temperature dependence of 200 hrs. self-welding characteristics on the selected hard facing materials and main structural materials of "MONJU" in 450 700C sodium purified by the cold trap temperature of 140C or 145C. The main results obtained are as follows. (1)The breakaway stress shows the apparent dwell temperature dependence. (2)The combinations of SUS 304/itself and SUS 316/itself self-weld above 500C and the breakaway stress increases linearly with the dwell temperature. (3)Ferritic steels exhibit the higher breakaway stress than austenitic stainless steels. (4)The combination of LC-1C/itself does not easily self-weld even at 700C. The combinations of Stellite No.6/itself, Colmonoy No.5/itself and Inconel 718/itself self-weld at 700C and do not self-weld at 600C. Only Colmonov No.5 breakaways at the inside as well as the self-welded interface. (5)Only Colmonoy No.5 shows the apparent corroded surface among the test materials after exposure to 700C sodium for 200 hrs. LC-1C exhibits flaking partially from the substratum. It is because the coating layer (0.2 mm thick) was too thick and there were the problems of the grid blast method on substratum surface and the manufacturing method on coating edge.