New Lubricants for Rotating Anode X-ray Tube Bearings

Period of Performance: 08/15/2000 - 02/14/2001


Phase 1 SBIR

Recipient Firm

Spire Corp.
One Patriots Park
Bedford, MA 01730
Principal Investigator


The project will develop new solid lubricant coatings for bearings that must operate at high rotational speed, high temperature, and under vacuum in rotating anode X-ray tubes for CT scanners and other medical and industrial applications. The lubricants will be applied by an ion- assisted process developed by Spire Corporation, in which an energetic ion beam both sputter-deposits the coating and concurrently bombards the deposited material. Ion bombardment initially modifies the substrate/coating interface to enhance adhesion, and continued bombardment during deposition densifies and homogenizes the microstructure for improved performance. The coating's composition can be far from phase-equilibrium, thus providing unique lubrication properties. In Phase I, we will identify and test promising coating materials based primarily on mixtures of silver and other ductile metals; a commercial manufacturer of X-ray tubes will test lubricated bearing balls in a rotating anode simulator, under realistic thermal-mechanical-vacuum conditions. Phase II would investigate a wider range of lubricant materials, processing parameters, and bearing components and initiate full-scale testing in actual X-ray tubes. PROPOSED COMMERCIAL APPLICATIONS: Bearing wear is the principal limitation on rotating anode X-ray tube lifetime in CT scanners and other X-ray equipment. New bearing lubricants could not only extend tube lifetime but also allow a major increase in X-ray intensity, along with proportional reduction of exposure time. An immediate commercial market exists for new solid lubricants for bearings in rotating anode X-ray tubes and in other precision machinery that operates in a vacuum environment.