Study on cavitation erosion resistance of bimodal grain copper alloy fabricated by laser shock peening

The surface of marine fluid operating machinery is commonly damaged by cavitation, and the protection of its surface is one of the key technologies in contemporary marine industry. Bimodal grain weaving is an important means to enhance the cavitation erosion (CE) resistance of materials. Traditional bimodal grain fabrication methods are based on the grain refinement-recrystallization principle or on the mixed powder sintering principle, which are too tedious. In this paper, laser shock peening (LSP), a convenient technique, is innovatively utilized to fabricate bimodal grain weaving on the surface of nickel-aluminum bronze (NAB), a material with excellent cavitation erosion resistance, by using the principle of inhomogeneity Gaussian beam laser shock peening. The mechanism of its cavitation erosion resistance is also investigated. The results show that the depth of the affected layer induced by laser shock peening can reach 460 μm. At a laser power density of 5.37∗107 J/cm2, a bimodal grain weave with a large number of micron-sized grains interwoven with ultrafine grains is formed on the NAB surface. The results of ultrasonic cavitation experiments show that the cavitation erosion resistance of bimodal grain surface fabricated by laser shock peening is improved by approximately 2.18 times than that of matrix. The synergy of strength and toughness of bimodal grains is one of the important reasons for the improved cavitation erosion resistance of NAB. This research is expected to further promote the application of bimodal grain weaving in the marine high-speed flow-passing components.