Wear and residual stress in high-feed milling of AISI H13 tool steel

Abstract

With the new manufacturing technologies, it has been possible to machine hard metals efficiently. During high-speed machining (HSM) of high-strength steel, the poor surface integrity of the workpiece affects the performance of the process. Surface roughness, microstructure, microhardness and residual stress are key performance indices for surface integrity directly controlled by tool wear and cutting parameters. In this study, high-feed milling (HFM) of a pocket on test samples made of DIN 1.2344 ESR mould steel with 55 HRc hardness was carried out on the CNC vertical milling machine. Three different cutting speeds and five different feed rates were used. At the end of the machining, tool wear was measured using a microscope. Subsequently, X-ray diffraction and hole drilling procedures were used to quantify residual stresses on machined test specimens. The results showed that under cutting conditions, the highest tensile residual stress was attained at f z = 0.78 mm·tooth−1, v = 127.58 m·min−1, and the highest compressive residual stress at f z = 0.5 mm·tooth−1, v = 127.58 m·min−1, on the workpiece surface. The most suitable cutting parameters were reported as f z = 0.63 mm·tooth−1 and v = 70 m·min−1 cutting speed when tool wear and residual stresses are considered together.