Research on surface hardened layer by two-passes plunge grinding

The grind-hardening of 40Cr steel was performed with creep feed grinding mode and different grinding pass. The microstructure and properties of the hardened layer were compared. The results show that there are similar martensitic structures and similar microstructure changing trend in the surface hardened layer, though initial structures are different during one-pass grinding and two-passes grinding. The depths and its uniformity of the surface hardened layer,its microhardness and wear resistance are further improved under two-passes grinding. But its maximum compressive residual stress and influencing depth reduces. Although the present study limits to two-passes grinding, the forming mechanism of the hardened layer is applicable to grind-hardening of multi-passes or quenched steel.