The effect of tool nose radius on surface integrity and residual stresses when turning Inconel 718™

• A systematic study examining nose radius has been performed.
• Surface alterations, cutting forces and residual stresses were measured.
• Higher levels of near surface tensile residual stress are found with increasing nose radius.
• A deeper tensile layer is produced and subsurface damage increases.
• Larger nose radius tools are not recommended for finish machining critical components.

This paper investigates the influence of tool nose radius on the residual stress distribution developed in Inconel 718 by finish turning. Although previous studies have shown that changes in rake angle, cutting edge geometry and nose radius can affect the tool performance and resulting workpiece surface integrity, no systematic study examining nose radius has been performed. Cutting force, microstructural alteration and residual stress distribution have been analysed for machining trials examining 2, 3, 4 and 6 mm radius tools at various feed rates and in both the new and worn tool condition. In general the results show that an increase in tool nose radius results in; increased radial cutting forces, increased microstructural deformation depth, higher near surface tensile stresses (up to 1550 MPa with a worn tool), and deeper tensile and compressive residual stress distribution.