Residual stress development in hard machining - a review

Metal machining processes require primarily cutting tool materials with high hardness, high resistance to the abrasive wear and thermal stability. The development of cutting tool materials results in advanced tool materials such are primarily ceramics, cubic boron nitride and sintered carbides which are considered to have the ability to cut hard materials. As a finishing process, the machined surface of the final product needs to control the surface quality. The quality of machined surface can be determined by properties such as surface roughness, hardness variations, micro-structural changes, residual stresses, etc. These properties belong to the surface integrity of the work piece material. The surface integrity affects significantly the mechanical properties of the parts such as fatigue limit, stress-corrosion resistance, dimensional stability, etc. This paper presents an experimental study to analyze the evolution of residual stresses in relation to the different parameter of machining. For precision milling of hardened steel, parameters are cutting speed and feed rate with a constant depth of cut. Two different cutting tool materials were used in this study, ceramic and cubic boron nitride. The results show that residual stresses near the machined surface of hardened steel are suitable for compressive stress. (paper)