Turning of interrupted and continuous hardened steel surfaces using ceramic and CBN cutting tools

In the machining of hardened steel surfaces, turning instead of grinding has been employed increasingly due to several advantages it offers, such as flexibility and the possibility of dry cutting. The main tool materials used for this purpose are CBN and ceramic due to their high hardness and, in the case of some grades of these materials, high chemical stability with iron. However, when interrupted surfaces are turned, the tool requires not only these properties but also sufficient toughness to resist impacts against workpiece interruptions. Therefore, the main goal of this work is to compare CBN and ceramic tools in continuous and interrupted cutting. To this end, several turning experiments were carried out on continuous surfaces (in this case, CBN with an added ceramic phase and a mixed ceramic were compared, due to their high chemical stability and hardness) and on interrupted surfaces (here, a high CBN content and a SiC-reinforced ceramic were compared due to their good ability to withstand impacts), applying different cutting speeds. The main conclusions of this work were that in both continuous and interrupted cutting, the CBN tools exhibited a much better performance with respect to both tool life and workpiece surface roughness than the ceramic tools.