Enhanced mitigation of cavitation erosion by means of femtosecond pulsed laser-induced hierarchical surface structures

Abstract

Hierarchical structures were fabricated on brass surfaces by means of a straightforward 2-step laser-scribing process. We tested the ability of these surface structures to withstand cavitation erosion and compared their performance to untreated brass samples. We found that hierarchical surface structures reduced the eroded volume by a factor between 7.2 and 22.7 times when compared to untreated samples after 800,000 cavitation events. Additionally, the hierarchical surface structures reduced the erosion by a factor between 1.1 and 1.5 times when compared to samples patterned with only microchannel surface structures, for the same amount of cavitation events. Up to 800,000 laser-induced cavitation bubbles were generated at a fixed standoff distance of 0.5 to test the mitigation effect of the scribed surface structures on the eroded volume. The eroded volume was computed by means of confocal microscopy. The results show that additional roughness imposed by the hierarchical surface structure acts as an energy dissipator as observed by comparing the sizes of the higher order rebound cavitation bubbles. These findings provide a promising solution for protecting equipment from cavitation erosion.