Cavitation Peening of Aerospace Bearings

High-value bearings are a critical part of the safety, reliability, cost and performance of modern aircraft. A typical passenger jet will have 100 to 175 high-valve bearings costing from $2,500 to $50,000 each for a total aircraft cost of $300,000 to $600,000. All gas turbine engine bearings are inspected at overhaul and typically 30-40% of there are rejected. For each engine overhaul, bearing replacement costs on average $100,000. Any process that increases bearing performance and reliability will have a commensurate effect on aircraft safety, reliability, performance and operating cost. In Phase I, Ormond demonstrated a novel surface enhancement process, cavitation peening, imparting deep, high magnitude residual stresses that are predicted to significantly enhance bearing life, reliability and performance. Preliminary fatigue results generated in Phase I look promising and analytical results indicate a fatigue life improvement of over 100% may be possible. Cavitation peening uses ultra-high pressure water jets to generate intense clouds of cavitation bubbles that collapse on the work piece generating shock waves that cold work the material. No particles are use, the process produces no waste and adds no weight to the part and is very inexpensive. The new technology is currently being evaluated by Boeing, Sikorsky, Bell and Rolls-Royce for aerospace applications and is proving particularly effective for gears. The company is also working with major bearing manufacturers Timken and SKF to investigate the value of the technology for bearing applications. The proposed Phase II work would refine the process, address readiness level issues and generate the fatigue data that is critical to wide spread acceptance of the cavitation peening technology.