Comparison between the improvements made to the fatigue strength of stainless steel by cavitation peening, water jet peening, shot peening and laser peening

Abstract

In order to make a clear comparison between the various peening methods used to improve the fatigue strength of stainless steel 316L, the fatigue strength of specimens treated by cavitation peening, water jet peening, laser peening and shot peening were examined using a plate bending fatigue test. Both cavitation peening and water jet peening were carried out using a submerged water jet system, and these are distinguished by the distance from the nozzle to the specimen. A submerged laser peening system was used for laser peening. The impact with the surface due to laser cavitation was greater than that due to laser ablation. For each peening method, the optimum coverage was examined by measuring the fatigue life at constant bending stress. Then, the fatigue strength of specimens treated with the optimum coverage was examined. The fatigue strength of the non-peened specimen was 279 MPa, whereas it was 348 MPa for cavitation peening, 325 MPa for shot peening, 303 MPa for laser peening and 296 MPa for water jet peening. The fatigue strength of each peening method was affected by the surface roughness and work hardening.