A bearing having bearing elements made of Type 60 Nitinol made by an investment
casting process for producing near net shape parts of Nitinol includes making a
ceramic mold having a series of spherical cavities, pouring molten Nitinol into
the mold cavities, cooling the mold and the Nitinol in the cavities to produce
solidified Nitinol balls, and breaking the mold away from the Nitinol balls. Nitinol
rods for roller bearings can be made by conventional casting directly from the
crucible in a draw-down oven. The bars are hot machined or hot rotary swaged and
then centerless ground and laser cut to length, or are first cut to length and
then centerless ground individually for crowned roller elements. The balls are
broken or cut from the risers, leaving the gates attached, and are consolidated
by healing under pressure in a hot isostatic press, then ground to the desired
size. The balls or rollers are polished, then treated to create an integral ceramic
finish. They are then repolished to produce an extremely smooth finish. The balls
can also be cut from a sheet or plate of the ball material as cubes or cylinders
and processed in an abrasive tumbler to round off the corners and edges, and the
rounded cubes or cylinders can hen be ground to spherical form in conventional
ball grinder.
