Cavitation Peening of Carburized Gears for Improved Fatigue Resistance

Cavitation peening is a novel method of inducing deep residual compressive stresses in metal components to enhance fatigue life and improve damage tolerance. The process involves sweeping ultra-high pressure waterjets over the surface of the part to be peened so that the cavitation bubbles form and collapse on the workpiece. The shock of the collapsing bubbles causes the formation of beneficial residual compressive stresses. Measurements of these stresses has shown that they extend much deeper into the material than is possible to achieve with conventional shot peening. Phase I results showed that the process works very well with carburized gears, improving the bending fatigue endurance limit from 90,000 psi to 135,000 psi stress level. The Phase II program proposes to build on this success by peening carburized gears for the V-22 program and quantifying the improved fatigue life. This low-cost peening method could improve transmission reliability by increasing fatigue life and reducing notch sensitivity of highly stressed transmission components. Success in this area will likely lead to other applications for the process.