The impact of mechanical properties on the cutting performance of Al₂O₃-based ceramic cutting tools for green turning of hardened steel

The utilization of green turning as an alternative to grinding has the potential to enhance the processing efficiency of hardened steel while also preserving the environment. However, the intermittent turning of hardened steel necessitates the tool to possess exceptional comprehensive mechanical properties. Consequently, this study aimed to investigate the impact of mechanical properties on the cutting performance of three Al2O3-based ceramic cutting tools, namely SG4, CC650, and CC670 by conducting interrupted turning experiments on hardened steel at both low and high speeds. The findings revealed that for different ceramic tool, it was not the smaller the speed, the smaller the cutting force when intermittently cutting hardened steels. In general, an optimal cutting speed existed where the workpiece material softened at a faster rate than the tool material due to cutting heat, resulting in minimized main cutting forces. Consequently, during the initial cutting stage, the cutting force of CC670 measured at 110 m/min was slightly higher than that at 230 m/min. The primary failure mechanism of CC670 at high speeds was mechanical fatigue. In high-speed cutting scenarios where tool failure was not primarily caused by thermal shock, the tool CC670, possessing superior mechanical properties, demonstrated a longer lifespan. When the multiple mechanical performance indices do not consistently reach their maximum values simultaneously under the current process conditions, an ideal cutting tool structure would feature a tool nose characterized by exceptional hardness and chemical stability, while the remaining section of the cutting tool should demonstrate high fracture toughness and flexural strength.