Effect of Tool Wear on Tool Life and Surface Finish when Machining DF-3 Hardened Tool Steel

Abstract

Hard turning is a dominant machining operation performed on hardened materials using single-point cutting tools. In recent years, hard turning operation has become more and more capable with respect to various machinability criteria. This work deals with machinability of hardened DF-3 tool steel with 55 ±1 HRC hardness at various cutting conditions in terms of tool life, tool wear mechanism and surface roughness. Continuous dry turning tests were carried out using coated, mixed ceramic insert with honed edge geometry. Two different cutting speeds, 100 and 210 m/min, and feed rate values of 0.05, 0.125 and 0.2 mm/rev were used with a 0.2 mm constant depth of cut for all tests. Additionally scanning electron microscope (SEM) was employed to clarify the different types of wear. As far as tool life was concerned, best result was achieved at lowest cutting condition whereas surface roughness values decreased when operating at higher cutting speed and lower feed rate. Additionally maximum volume of material removed is obtained at low cutting speed and high feed rate. Dominant wear mechanism observed during the experiments were flank and crater wear which is mainly caused by abrasive action of the hard workpiece material with the ceramic cutting tools.