An Experimental Investigation on the Surface Properties of Small-Diameter Deep Holes in 2A11 Aluminum Alloy via Water Jet Peening

Abstract Focusing on the water jet peening (WJP) of 2A11 aluminum alloy small-diameter deep holes, this study addresses the challenges of processing such geometries by evaluating the effect of jet pressure on their surface properties. Experiments were conducted using a self-designed WJP system. The peened surfaces were characterized using a surface roughness tester, a microhardness tester, and a digital microscope to measure surface roughness and microhardness, and to observe surface morphology, respectively. Analysis of how surface roughness and microhardness correlate with jet pressure demonstrated that the 50–60 MPa interval effectively removed machining scratches and improved surface quality. However, at a jet pressure of 70 MPa, excessive jet impact caused surface damage, leading to degraded surface quality. The gradients between peaks and valleys in the surface roughness profile exhibit gentle, rounded transitions, which help alleviate stress concentration. Simultaneously, WJP significantly enhanced the surface microhardness of the 2A11 alloy, with the microhardness value increasing markedly as the jet pressure increased. This study provides a technical foundation for the application of WJP to small-diameter deep holes in 2A11 aluminum alloy.