Cavitation abrasive integrated waterjet peening process and the effect of process parameters on the surface integrity of TA19 titanium alloy

Abstract

Waterjet peening has emerged as a potential surface treatment technology, which is gradually being used to improve the surface integrity and mechanical behavior of metal materials. Submerged abrasive waterjet peening, which combines cavitation peening and abrasive waterjet peening and called cavitation abrasive integrated waterjet peening (CAI-WJP), is proposed in this paper and was studied experimentally. The principle of CAI-WJP is first introduced. The effect of the CAI-WJP parameters (i.e., water pressure, standoff distance, traverse speed, path interval, and peening angle) on the surface integrity of TA19 titanium alloy was systematically investigated. Results show that the specimen treated with CAI-WJP using different process parameters formed a plastic deformation layer with a depth of 5–45 μm. The minimum surface roughness of Ra obtained by CAI-WJP was 0.348 μm, which is 28.5% lower than the as-received surface. The maximum surface microhardness increased by up to 21.1%, with a maximum work hardening depth of 150 μm. The surface compressive residual stress (CRS) increased to approximately 640–800 MPa compared with the original CRS of 50–80 MPa on the as-received specimen, and a maximum CRS depth of 360 μm was obtained. The microstructure evolution on the topmost surface and subsurface of the specimen treated with CAI-WJP with a water pressure of 100 MPa was observed by transmission electron microscopy, which showed that nanocrystallization with amorphization occurred, and nanocrystals with an average size of 6.9 nm formed on the topmost surface. In addition, many dislocation cells and tangles formed on the subsurface with a depth of 15 μm, and a number of dislocation loops, walls, and pinning were found at the depth of 150 μm. This work verifies the effectiveness of the proposed CAI-WJP and provides a favorable reference for how to pick up optimized CAI-WJP process parameters.