Contribution to the study of the cutting mechanisms during high speed machining of hardened steel

A 100Cr6 steel with a hardness HRC62 was machined. Quick stop tests were carried out to observe the different chip formation mechanisms. A limit was found between the shearing or cracking chip formation. Experimentations for the selected steel at HRC62 were led at various cutting speeds and feed rates. The `saw tooth chips' obtained were examined geometrically and metallurgically on longitudinal midsections. Relations have been established between the chip geometry and the cutting conditions. A theoretical study on the chip shape was made, in particular about its thickness. The friction stick slip velocities, as the segment apparition frequency were calculated. Each stage of the chip formation could be observed on each micrography of Q.S.T, especially the crack initiation.