Pre-mixed abrasive waterjet peening with post-low stress milling process and the effect of process parameters on the surface integrity of TC11 titanium alloy

Pre-mixed abrasive waterjet peening (PAWJP) is progressively gaining traction in enhancing metal materials’ surface integrity and mechanical behavior. To avoid the disadvantage of PAWJP in the application, a hybrid manufacturing method of pre-mixed abrasive waterjet peening with post-low stress milling (PAWJP-LSM) is proposed and studied experimentally. The principle of PAWJP-LSM was first introduced. Subsequently, the effect of the PAWJP-LSM parameters (i.e., abrasive type, traverse speed, nozzle inlet pressure, and removal amount) on the surface integrity of TC11 titanium alloy and its variation trend were systematically investigated. Results show that the specimen treated with PAWJP using different process parameters formed a PAWJP treatment area with a strengthening depth of 6–275 μm. The minimum surface roughness obtained by PAWJP was 0.727 μm. The maximum surface microhardness significantly increased to approximately 516.3 HV from 402.8 HV, with a maximum micro-hardness rate of 28.2 % and a maximum work hardening depth of 225 μm. The surface compressive residual stress (CRS) induced by PAWJP ranged from −97 to −322 MPa, with a maximum CRS exceeding −890 MPa and a maximum CRS layer thickness of 305 μm. The surface integrity of PAWJP-LSM is further enhanced compared to PAWJP, resulting in a 98.9 % reduction in minimum surface roughness and a 73.7 % reduction compared to the as-received surface roughness. Additionally, PAWJP-LSM exhibited a 98.9 % increase in surface CRS and a 19.4 % increase in maximum CRS. Moreover, the fatigue life was significantly improved by 69.4 %, which was 294.5 % higher than that of the as-received specimen. Nanocrystals with an average size of 27.3 nm were formed in the topmost surface. Overall, the PAWJP-LSM method demonstrated significant potential for engineering applications and exhibited substantial value in the surface treatment of TC11 alloy. This study validated the effectiveness of the proposed PAWJP-LSM method and provided a valuable reference for selecting optimized process parameters.