Surface integrity in longitudinal-torsional ultrasonic-assisted milling of 18CrNiMo7-6 steel

A systematic experimental comparison between conventional milling (CM) and longitudinal-torsional ultrasonic-assisted milling (LTUAM) was carried out to evaluate their influence on the surface characteristics of 18CrNiMo7-6 steel. Experimental data reveal that with elevated cutting speeds, both LTUAM and CM showed increases in surface roughness, microhardness (peak enhancements of 10.2% and 20.1%, respectively), and surface tensile residual stress (maximum increments of 216.6 MPa and 225.89 MPa, respectively). Conversely, when examining feed rate variations, LTUAM displayed marked superiority over CM: achieving up to 27.1% reduction in surface roughness, 6.2% improvement in microhardness, and 78.1% reduction in surface residual stress magnitude compared with CM under identical cutting conditions. This investigation delivers essential insights for implementing ultrasonic processing of 18CrNiMo7-6 steel, offering substantial value for precision manufacturing applications.