Fig. 1. Morphologies of Lc-Sr-31 powder

Fig. 2. Schematic of coaxial powder feeding laser cladding process

Fig. 3. Test diagrams of residual stress of cladding layer. （a） Photo； （b） schematic

Fig. 4. Microstructures of cladding layer. (a) Without preheating; (b) 300 ℃ preheating temperature

Fig. 5. Energy spectrum analysis of cladding layer. (a) Without preheating； (b) 300 ℃ preheating temperature

Fig. 6. EDS line scanning of cladding layer without preheating. (a) Line scanning diagram; (b) element intensity change

Fig. 7. EDS line scanning of cladding layer with 300 ℃ preheating temperature. (a) Line scanning diagram; (b) element intensity change

Fig. 8. Microstructures of cladding layer without preheating. (a) M₂₃C₆ phase; (b) M₇C₃ phase

Fig. 9. Microstructures of cladding layer with 300 ℃ preheating temperature. (a) M₂₃C₆ phase; (b) （c） M₇C₃ phase

Fig. 10. Microhardness of cross-section with different preheating temperatures

Fig. 11. Microstructures of heat affected zone with different preheating temperatures. (a) Without preheating; (b) 100 ℃ preheating temperature; (c) 200 ℃ preheating temperature; (d) 300℃ preheating temperature

Fig. 12. Effect of preheating temperature on residual stress in X direction. （a） Without preheating； （b） 100 ℃； （c） 200 ℃； （d） 300 ℃

Fig. 13. Effect of preheating temperature on residual stress in Y direction. （a） Without preheating； （b） 100 ℃； （c） 200 ℃； （d） 300 ℃

Fig. 14. Stress at different preheating temperatures

Fig. 15. XRD at room temperature and 300 ℃ preheating temperature