An investigation on the influence of different cooling/lubrication techniques on the tool wear and surface integrity in the hard turning of AISI 52100 bearing steel

From the eco-friendly cutting perspective, sustainable manufacturing can be regarded as a solution to improve tool life and product quality. In this context, the studies on different cooling/lubrication techniques employed during hard machining have increasingly become more popular in the literature. This study investigates the performance of eco-friendly cooling/lubrication techniques (MQL, cryogenic and hybrid) in the hard turning of AISI 52100 bearing steel using the wiper and conventional CBN (cubic boron nitride) inserts. The experiments are performed at a cutting speed of 200 m/min, a feed of 0.1 mm/rev and a depth of cut of 0.1 mm. For each machining condition, tool wear, surface roughness (Ra and Rz) and residual stress (axial and hoop) values are measured. On the other hand, the cutting force and subsurface layer thickness measurements are conducted in order to support the obtained results. Experimental results show that MQL+CO2 condition significantly reduces wear formations (flank and crater wear) on conventional and wiper inserts under all test conditions generally. Additionally, lower roughness values (Ra < 0.15 µm) are obtained using the wiper inserts whereas the conventional inserts produce higher roughness results (Ra > 0.26 µm) under all cooling/lubrication conditions. Besides, MQL+CO2 and wet conditions provide the best surface roughness results for the wiper and conventional inserts respectively. In addition, it is observed that the magnitudes of residual stresses are significantly affected by cooling/lubrication conditions and tool geometry. The compressive residual stresses are produced at surface and subsurface of the work material up to depth of 30 µm under all test conditions. In general, in case of the conventional and wiper inserts, wet and MQL conditions generate maximal compressive stresses in comparison to other conditions. In addition, it is found that wiper inserts produce more compressive stresses when compared to the conventional inserts. Finally, this study shows that it is possible to obtain better surface roughness, tool wear and residual stress values for the wiper inserts under hybrid conditions, especially MQL+CO2 conditions