Workpiece Surface Integrity when Milling Udimet 720 Superalloy

The paper details a comprehensive investigation into the surface integrity of Udimet 720 following end milling under different environment conditions (dry, flood, higher pressure and MQL) and cutting speed (25 and 50m/min). Surface roughness (Ra) was < 0.25 μm regardless of tool condition with no white layers detected on any of the samples analysed. Residual stress measurements indicated surface compressive stress of 120 MPa on workpieces milled using new cutters under MQL environment. In contrast, worn tools produced surface tensile stresses of ∼80 MPa, with subsurface compressive residual stress of up to ∼400 MPa at a depth of 80 μm.