Study of quenched steels machining with a polycrystalline Hexanite-R cutting tool

The cBN based superhard material is well known in the modern industry of steel machining. A cBN modification that has been developed in recent years refers to wBN, which presents some unique properties: close to diamond hardness, high thermal conductivity, chemical inertia to iron, high dynamical strength, high wear resistance, etc. In this study, a wBN modification, called “Hexanite-R” employed as a cutting insert, was chosen. The research of this tool capacity was carried out in the machining of a quenched ASTM 4140 steel. The axial velocity was 0.11 mm/rotation, the cutting depth used was 0.3 mm, with a cutting velocity of 150 m/min. The tool life for machining a steel with Rz (6.3–1.6 μm) and Ra (1.25–0.32 μm) roughness was of 90 min for the HRC 58–60 hardness steel, and 150 min for the HRC 48–52 hardness steel, which corresponds to a life-span 10 times superior to that of the hard metal one. The tool wear dependence was determined on the machining steels time with some thermal treatments. Besides this, an experiment was also carried out to determine the tool life-span under machining quenched shafts with axial holes, looking for the possibility of substituting the grinding operations in this case.