Performance of conventional and wiper CBN inserts under various cooling conditions in hard turning of AISI 52100 steel

Cryogenic cooling and minimum quantity lubrication (MQL) are regarded as effective green manufacturing techniques since they eliminate the excessive utilization of conventional cutting fluids (CCFs) that are known to have adverse impacts on both the environment and human health. Moreover, these methods have promising effects on surface integrity in machining hard-to-cut materials. This study investigates the impact of hybrid and cryogenic lubri-cooling methods on surface integrity (surface roughness, microhardness, and residual stresses) in hard turning of AISI 52100 bearing steel (62 HRC) with conventional and wiper CBN inserts. For that purpose, a precooling-based hybrid (a combination of precryogenic cooling of the workpiece and MQL) and direct cryogenic cooling techniques were used for comparison during the hard turning tests. The tests were carried out at a constant cutting speed (200 m/min), feed (0.1 mm center dot rev(-1)), and depth of cut (0.1 mm) under dry, carbon dioxide (CO2), liquid nitrogen (LN2), CO2 + MQL, and LN2 + MQL conditions. The results show that hybrid lubri-cooling condition (CO2 + MQL) improved the surface quality and increased the compressive residual stresses at the machined surface when wiper inserts were employed. On the other hand, effective cooling under direct CO2 condition provided better surface integrity when machining with conventional inserts.