Study on the failure mechanism and improvement measures of bearings in the full-ocean-depth ultra-high-pressure seawater pump

Under ultra-high-pressure full-ocean-depth conditions, the rolling bearings of seawater pumps are often subjected to coupled stress conditions, including high external pressure, oil-water emulsification, and sustained high loads. Early failure tends to occur, which severely compromises system stability and reliability. This study focuses on identifying the typical failure mechanisms of bearings and proposing key optimization measures. A high-pressure experimental system rated at 120 MPa was constructed. Long-term water injection and drainage cycling tests were performed, followed by teardown inspections of failed prototypes. The bearing degradation was found to involve multiple failure modes, including rolling element fracture, cage breakage, lubricant emulsification, and three-dimensional embedded abrasive wear. The combined effects of lubricant degradation and particulate contamination primarily caused these failures. Comparative tests were conducted on ceramic bearings, PEEK bearings, and tapered roller bearings. The results confirmed that the tapered roller bearing exhibited superior environmental adaptability under lubrication with No. 10 aviation hydraulic oil. To enhance system performance, two engineering measures were proposed: (1) the use of heavy-duty tapered roller bearings to increase load capacity and fatigue life; (2) the addition of molybdenum disulfide (MoS₂) anti-wear additives to the lubricant to improve lubrication stability and wear resistance. Validation results showed that, after optimization, the prototype achieved significantly higher mechanical efficiency under 120 MPa conditions, and bearing wear was substantially reduced. These findings provide theoretical support and engineering guidance for selecting bearings and developing lubrication strategies in high-pressure, deep-sea hydraulic systems.