Experimental Parameter Investigations on the Tribological Behavior of Stellite 6 in Liquid Sodium

The friction and wear behavior of various material combinations was studied in a liquid-sodium loop up to fluid temperatures of 900 K to guarantee selfalignment and safe operation of liquid-metal-cooled fast breeder reactor (LMFBR) components, such as subassemblies, control and shutdown units, instruments, and centering pads. Pin-on-disk, plate-on-plate, and tilting plane test section systems were used. Numerous material combinations exhibiting good corrosion resistances in liquid sodium were investigated under identical operating conditions. Those revealing the lowest wear rates and the lowest friction coefficients were subject to parameter tests. The influences on friction and wear behavior of friction velocity, contact force, sodium temperature, equipment criteria, and tribochemistry were studied. The experimental results are shown for a Stellite 6-Stellite 6 combination. They revealed friction and wear coefficients to be clearly below the set limits. However, this material combination has a high cobalt content and is therefore no optimum choice with respect to contamination problems of the primary system of an LMFBR. Other experiments are necessary to develop materials with zero contamination effects.