Shot-peening effects on metal erosion

Material damage by several erosion processes is caused mainly by high, local, and repetitive loading, resulting in fatigue, cracking, and erosion. One of the surface treatments used to increase material resistance to erosion damage is shot peening. This process induces compressive stresses on the treated surface layer, and increases its resistance to fatigue loading. Cumulative erosion-time curves of shot-peened specimens clearly indicate their increased erosion resistance compared to that of machined specimens. However, this comparison does not yield any information about the causes for the improved performance. Cumulative erosion-time plots in the Weibull domain of machined specimens, tested by five different erosion methods, are very similar. The common plot shape is bimodal with a decreasing slope. These plots enable an extensive study of machined and shot-peened specimens. This study explains the improvement process, and quantifies it during test duration and beyond it. This method is illustrated by testing of two AISI-316 specimens by the vibratory cavitation erosion method. Analysis of test results confirms the effectiveness of this method for erosion testing of machined and shot-peened specimens. Shot peening was found to restore some of the erosion properties of the boundary layer, bringing them closer to those of the base material.