Fig. 1. Microstructure of 42CrMo steel matrix

Fig. 2. Schematic of laser-induction hybrid quenching on 42CrMo steel

Fig. 3. Microhardness curves of laser-induction hybrid quenching hardened layers

Fig. 4. Physical model and locations of feature points

Fig. 5. Schematic of rolling wear test device

Fig. 6. Microstructure of laser-induction hybrid quenching hardened layer

Fig. 7. Residual stress distributions of hardened layer samples with different depths. (a) Residual stress distribution of 3.5 mm depth specimen along X direction; (b) residual stress distribution of 3.5 mm depth specimen along Y direction; (c) residual stress distribution of 4.5 mm depth specimen along X direction; (d) residual stress distribution of 4.5 mm depth specimen along Y direction; (e) residual stress distribution of 6.3 mm depth specimen along X direction; (f) residual stress distribution of 6.3 mm depth specimen along Y direction

Fig. 8. Surface damage morphologies of fatigue specimens with different depths of hardened layers. (a) Specimen with 3.5 mm depth; (b) specimen with 4.5 mm depth; (c) specimen with 6.3 mm depth

Fig. 9. Three-dimensional morphologies and two-dimensional profiles of cross-section for fatigue specimens with different depths of hardened layers. (a) Specimen with 3.5 mm depth; (b) specimen with 4.5 mm depth; (c) specimen with 6.3 mm depth

Fig. 10. Sectional crack morphology of fatigue specimen with hardened layer depth of 3.5 mm

Fig. 11. Sectional crack morphology of fatigue specimen with hardened layer depth of 4.5 mm

Fig. 12. Sectional crack morphology of fatigue specimen with hardened layer depth of 6.3 mm

Fig. 13. Schematic of surface cracking under heavy load condition

Fig. 14. Schematic of internal cracking under heavy load condition

Table 1. Chemical composition of 42CrMo steel

Table 2. Element distribution in area A in Fig. 12