Symptoms of cavitation erosion
The surface of the bearing exhibits areas where material has been removed or eroded during operation. The depth of these damages is often limited to the immediate surface of the material, however, if the bearing system is allowed to operate under these conditions for prolonged periods then the damage can penetrate deep into the bearing material, in extreme cases through to the steel backing.
Possible Causes
Cavitation erosion results from rapid fluctuations in oil film pressure. When the pressure in an isolated area of the oil film drops below the bulk vapor pressure of the oil, a small, vapor-filled cavity is formed. This cavity then travels to an area of higher pressure where it collapses with the surrounding oil impinging on the adjacent bearing material. This action can eventually erode the bearing surface. The occurrence of cavitation erosion damage is prevalent in high-speed engines, bearing systems operating under high clearance conditions, and poorly designed oil groove and feeding configurations.
Prevention
Reduce operating clearance, increase supply oil pressure, change to a higher viscosity oil. Re-evaluate oil groove and feeding configuration of the bearing system; the practicality of blending edges or contours of grooves to promote streamline flow or change to a harder more resistant bearing material. The harder the bearing material the greater its resistance to cavitation erosion.
