Process Controls for Surface Integrity Generated by Hard Turning

An investigation was conducted on the evolution of the residual stresses and re-hardened white layer during finish hard turning. The residual stress pattern is dominated by changes in cutting forces resulting from tool wear. Increased flank wear accelerated normal sliding force generating tensile residual stress at the surface and reducing the magnitude of compressive stress below the surface. However, very high flank wear yielded maximum below-surface compressive residual stress. Increased tool wear beyond a critical value led to discontinuity in the relationship between normal and tangential forces. This paper proposes a new tool-life criterion for controlling surface integrity in finish hard turning.