Ceramic Airframe Bearings.

A friction and wear screening investigation of ceramic coatings, lubricants, and lubricant reservoir designs was conducted for an 1100 F bearing application. A slotted reservoir design was evaluated in both elevated- and room-temperature screening tests. Load-spectrum and life bearing tests were conducted on a cylindrical lubricant reservoir design. These tests demonstrated a maximum load capacity of 22,000 psi and a life of 19,862 cycles at 15,000 psi. An improved lubricant reservoir ceramic bearing design was developed using a hot-pressed silicon nitride ball sliding aginst an alumina coating on titanium. Tests conducted with the slotted reservoir design bearings at elevated temperatures resulted in early failure of the bearing. Axial cracks in the silicon nitride ball were the apparent cause of bearing failure. Room-temperature tests of the slotted reservoir design were conducted under conditions simulating a hydrofoil flap hinge application. The tests demonstrated a significant improvement in performance. A maximum load capacity of 28,000 psi and a wear life of 60,000 cycles at 15,000 psi were obtained with this design. Author