Effects of Ultrasonic Surface Rolling Parameters on Surface Integrity of TC17 Alloy

The main purpose of this paper was to investigate the effects of different static forces and feed speeds of ultrasonic surface rolling (USR) on the surface integrity of TC17 alloy. Surface roughness, in-depth residual stress, in-depth microhardness, and cross-sectional microstructure of the processed materials were measured and analyzed to get a comprehensive knowledge of the surface characteristics under different conditions. The results indicate that the specimens treated by USR achieve a considerable improvement in surface roughness (R_a 0.04-0.10 μm); meanwhile, the surface morphology is smooth and uniform. Moreover, the surface residual stress and microhardness are greatly improved compared to those of untreated specimen. The maximum compressive residual stress is approximately − 966 MPa at the depth of 300 μm, and the thickness of strengthened layer is about 1000 μm. The material of affected layer experiences plastic deformation in a certain extent. Moreover, the gradient change in microstructure and white layer are also observed on the subsurface layer. It is also concluded from the study that static force has a more significant impact on surface integrity characteristics compared with feed speed.