Effect of LN2 and CO2 Coolants in hard turning of AISI 4340 steel using tungsten carbide tool

Recently, Cryogenic cooling has witnessed a significant role in improving efficiency, increasing the quality of machined parts, and developing a techno-economic and eco-friendly acceptable methodology in the machining of components. This study deals with the effect of hardened AISI 4340 steel at 48 HRC against uncoated WC cutting tool analysed through the use of dry, cryogenic liquid nitrogen (Cryo-LN2) and cryogenic liquid carbon dioxide (Cryo-LCO2) cooling environments. The input parameters for this hard turning condition include cutting velocity, feed rate, and depth of cut. A study of the machining performance of cutting temperature, surface roughness, material side flow, flank wear, microhardness, and chips morphology have also been made. The experiment results revealed the effective lowering of the cutting temperature, better surface roughness and reduced flank wear for LCO2 and LN2 coolant by cryogenic cooling against dry cutting condition. Compared to dry and cryogenic LCO2 cutting environments, the machined zone of a cryogenic LN2 exhibited the highest microhardness value. The main reason for this was the decrease in the thermal softening effect. Overall, the performance of the cryogenic LN2 environment condition was effective and efficient in the turning process compared to dry and cryogenic LCO2.

Automated summary

This study investigates the effect of cryogenic cooling with liquid nitrogen and liquid carbon dioxide on the machining of hardened AISI 4340 steel. The results show that cryogenic cooling can lower the cutting temperature, improve surface roughness, and reduce flank wear. In particular, the machining zone with cryogenic liquid nitrogen exhibits the highest microhardness value.