Research on surface integrity of AISI M2 workpiece hard-turning precision machining with cubic boron nitride cutting tool

Abstract. To investigate the surface integrity of AISI M2 workpieces during hard turning with a cubic boron nitride tool, the surface morphology, metamorphic layers, and mechanical properties of 18 hard-turning experimental samples were characterized using scanning electron microscopy and other analytical instruments. The results showed that the machined surface morphology had good consistency, but there were defects such as turning grooves. The turning feed had the most significant influence on the three-dimensional surface roughness Sa: when the feed rate increased from 0.05 to 0.2 mm r−1, Sa increased from 0.824 to 5.795 µm. When the turning speed was lower than 200 m min−1, the white layer thickness was positively correlated with the turning speed (approximately 0.32 µm at 200 m min−1), while a negative correlation was observed when the speed exceeded 200 m min−1 (approximately 0 µm at 360 m min−1). As tool wear increased from 0 to 0.2 mm, the white layer thickness increased by 143.75 %. The surface residual stress was mainly compressive stress, with the maximum axial compressive stress (−72.1 ± 7 MPa) observed at a turning speed of 160 m min−1. The metamorphic layer significantly increased the surface hardness. This study provides a reference for improving the service life of AISI M2 workpieces.