Friction Behavior of Cobalt Base and Nickel Base Hardfacing Materials in High Temperature Sodium

A friction behavior of the hardfacing materials such as cobalt base alloy “Stellite” and nickel base alloy “Colmonoy” used in the sliding components of a sodium cooled fast breeder reactor was investigated in various sodium environments. Also, friction tests on these materials were carried out in argon environment. And they were compared with those in sodium environment.The results obtained are as follows:(1) In argon, the cobalt base hardfacing alloy showed better friction behavior than the nickel base hardfacing alloy. In sodium, the latter was observed to have the better friction behavior being independent of the sodium temperature.(2) The friction coefficient of each material tends to become lower by pre-exposure in sodium. Particularly, this tendency was remarkable for the nickel base hardfacing alloy.(3) The friction coefficient between SUS 316 and one of these hardfacing materials was higher than that between latter materials. Also, some elements of hardfacing alloys were recognized to transfer on the friction surface of SUS 316 material.(4) It was observed that each tested material has a greater friction coefficient with a decrease of the oxygen content in sodium.