Abstract: White layer is a unique phenomenon of high-speed hard machining and has significant effects on machined surface integrity and service performance. Focusing on the white layer in high-speed hard machining, the high-speed hard cutting experiment of hardened GCrl5 bearing steel and white layer tests are conducted. The formation mechanism of white layer under various cutting conditions is investigated, and the influence of the cutting speed and flank wear on white layer’s features is studied. Analysis results show that the thickness of white layer increases with increasing cutting speed and flank wear, and the uniformity and continuity of the distribution of white layer decreases. Increasing cutting speed and flank wear will increase cutting temperature and result in rapid quenching effect of the machined surface, which causes an increasing of the thickness of white layer. The cutting speed has a more significant influence on the white layer than flank wear. The formation mechanism of white layer is plastic deformation at lower cutting speed (about 100 m/min), and is martensitic phase transformation when the cutting speed exceeds 300 m/min. The formation mechanism of white layer at midrange speed (about 200 m/min) is a hybrid effect of plastic deformation and martensitic phase transformation.

Key words: hard machining, high-speed machining, machined surface, white layer