Fig. 1. Images of reinforced area. (a) Front image; (b) cross-sectional image

Fig. 2. Metallographic structures of different areas. (a) Strengthened area; (b) heat-affected zone; (c) matrix area

Fig. 3. SEM morphologies at different positions of strengthened zone. (a) Local morphology of strengthened zone; (b) position A, surface morphology of strengthened zone; (c) position B, morphology in the middle of strengthened zone; (d) position C, morphology of side edge of strengthened zone; (e) position D, morphology of bottom edge of strengthened zone

Fig. 4. Schematic of the line scanning direction of the energy spectrum in strengthened zone

Fig. 5. Spectral diagram of strengthened zone along the scanning direction

Fig. 6. Schematic of the position of microhardness testing points

Fig. 7. Microhardness curves of samples before and after laser strengthening

Fig. 8. Polarization curves of samples before and after laser strengthening

Fig. 9. Friction coefficient versus time for samples before and after laser strengthening

Fig. 10. SEM morphologies of samples before and after laser strengthening. (a) Before laser strengthening; (b) after laser strengthening