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

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

Fig. 3. Photo of thermal fatigue testing machine

Fig. 4. Shape and size of thermal fatigue specimen

Fig. 5. Crack propagation pattern on the surface of cladding layer and sampling diagram. (a)Crack propagation pattern; (b) sampling diagram

Fig. 6. Thermal fatigue crack length test. (a) Schematic of sample crack length test; (b) software statistics of crack length

Fig. 7. Thermal fatigue crack propagation of matrix material

Fig. 8. Crack morphologies in thermal fatigue process of matrix material. (a) 400 thermal cycles; (b) 500 thermal cycles; (c) 900 thermal cycles; (d) 1000 thermal cycles; (e) 1500 thermal cycles ; (f) 2000 thermal cycles

Fig. 9. Microstructure changes of matrix material after 2000 thermal cycles. (a) Original microstructure; (b) (c) microstructure and its partially enlarged view after 2000 thermal cycles

Fig. 10. Relationship between the number of thermal cycles and crack length for matrix and cladding samples

Fig. 11. Oxidation corrosion pit on the interface. (a) 80 thermal cycles; (b) 120 thermal cycles; (c) 160 thermal cycles

Fig. 12. Transverse crack at the interface. (a) 500 thermal cycles; (b) 1000 thermal cycles

Fig. 13. Crack passivation. (a) 1500 thermal cycles；(b) 2000 thermal cycles

Fig. 14. Effect of preheating temperature on thermal fatigue property of cladding layer

Fig. 15. Microstructures of cladding layer before heat treatment.(a) M₇C₃ hard phase at grain boundary; (b) M₂₃C₆ type intragranular carbide

Fig. 16. Position of energy spectrum analysis points of cladding layer before heat treatment

Fig. 17. Microstructures of cladding layer after heat treatment. (a) Zone 1； (b) zone 2

Fig. 18. Position of energy spectrum analysis points of cladding layer after heat treatment

Fig. 19. Macro morphologies of heat-treated cladding samples during 2000 thermal cycles. (a)(b) 500 thermal cycles; (c)(d) 1000 thermal cycles; (e)(f) 1500 thermal cycles; (g)(h) 2000 thermal cycles

Fig. 20. Morphologies of notch at the tip of heat-treated cladding sample after 2000 thermal cycles. （a） Whole view; (b) enlarged A zone; (c) enlarged B zone; (d) enlarged C zone

Fig. 21. Microstructures of heat-treated cladding sample before and after 2000 thermal cycles. (a) Before thermal cycles; (b) after 2000 thermal cycles