Analysis of the white layers formed during machining of hardened AISI 52100 steel under dry and cryogenic cooling conditions

The present work aims at understanding the effects of cryogenic coolant application and machined surface alterations during orthogonal machining of hardened AISI 52100 bearing steel. Experiments were performed under dry and cryogenic cooling conditions using cubic boron nitride tool inserts with varying initial hardness and tool shape. Several experimental techniques were used in order to analyze the machined surface. In particular, optical and scanning electron microscopes were used for characterizing the surface topography, whereas the microstructural phase composition analysis and chemical characterization have been performed by means of X-ray diffraction and energy-dispersive spectroscopy techniques. The experimental results prove that the white layer is partially reduced or can be totally eliminated under certain process parameters and cryogenic cooling condition.