A Comparative Study of Dry Turning Performance of 4340 Alloy Steel with As-Received and Cryogenically Treated Coated Cermet Cutting Tools

Cryogenic treatment has been shown to significantly improve the cutting performance of inserts. Alloy steel grade 4340, renowned for its high impact and abrasion resistance, has extensive application in aircraft landing and high-power transmission gears. In this study, a comparative characterization (microhardness and XRD profile) and dry turning performance evaluation (turned surface roughness and insert wear) of alloy steel grade 4340 were performed using as-received and cryogenically treated coated cermet cutting inserts. The turning operation was carried out with various cutting velocities ( 55, 90, and 150 m/min) and a constant feed and cutting depth (0.111 mm/rev and 1 mm) under dry cutting conditions. The cryogenically treated insert obtained A reduced Ra value compared to untreated conditions at all cutting speeds. In addition, Ra value was reduced to a maximum of 29%. A lower level of insert wear and chip particle deposition at the cutting point was observed with cryo-treated inserts. Finally, it was revealed that the better machining characteristics in terms of reduced Ra values and insert wear with cryo-treated conditions were due to the enhanced wear resistance over the untreated conditions.