Tool Life and Process Dynamics in High Speed Ball End Milling of Hardened Steel

In this paper, a comparison of tool life of sintered carbide (with TiAlN coating) and cubic boron nitride (CBN) ball end mills is presented. Experiments were carried out on hardened steel X155CrVMo12-1 plate during milling process with a constant surface inclination angle (α) and variable cutting speeds (vc) and feeds (fz). Cutting forces (Fi) were measured and presented in function of tool wear (VBB). Specific cutting pressures were also estimated in function of tool wear (VBB). Their values are applied to cutting force model formulation, which includes tool wear. The research revealed that in certain range of cutting speed tool life acquired for sintered carbide can be higher than that obtained for cubic boron nitride tool. It was observed, that for cubic boron nitride cutter abrasive wear was dominant independently of cutting speed. In case of sintered carbide, catastrophic wear of cutting edge was found for cutting speed vc = 500 m/min.