Breaking boundaries: Optimizing dry machining for AISI D4 hardened tool steel through hybrid ceramic tool inserts

The conventional approach to high-speed turning of AISI D4 hardened steel often encountered challenges, notably elevated temperatures at the tool–workpiece interface and resultant surface quality degradation, particularly when utilizing CBN and ceramic inserts at cutting speed exceeding 200 m/min. In response to these limitations, this study presents a novel methodology employing a coated tin layered insert comprised of aluminum oxide (Al₂O₃)-Ti (C, N) for dry machining of AISI D4 steel. A significant contribution of this work lies in establishing a quantitative relationship between process variables and response characteristics, alongside process optimization facilitated by the Taguchi method design of experiment approach. By employing a selected hybrid ceramic insert, the study achieves sustainable dry machining of AISI D4 steel. Multiresponse analysis reveals that optimal machining parameters include a cutting speed (C_s) of 170 m/min, feed rate of 0.03 mm/rev, and depth of cut (DoC) of 0.4 mm, resulting in a minimum surface roughness of 0.76 µm. Analysis of variance underscores the pivotal role of feed rate and DoC in shaping surface characteristics, with statistical significance (p-value <.05), while cutting speed proves insignificant (p-value >.05). Furthermore, SEM micrographic examination substantiates the superior performance of hardened D4 steel, renowned for its exceptional resistance to wear and oxidation, rendering it indispensable in the fabrication of various tools including dies, press tools, punches, and bushes, surpassing current machining methodologies.