Fig. 1. Schematic of laser cladding test device

Fig. 2. Schematics of hardness testing plane. (a) 3D view; (b) cross section

Fig. 3. Three-dimensional finite element model of single pass cladding layer. (a) Overall view; (b) cross section

Fig. 4. Thermophysical properties of M2 steel and Cr12MoV steel. (a) Density; (b) specific heat capacity; (c) thermal conductivity;

Fig. 5. Macroscopic morphologies of single-pass cladding layer before and after substrate preheating. (a) Unheated surface; (b) unheated cross section; (c) preheated surface; (d) preheated cross section

Fig. 6. Longitudinal section morphologies of single-pass cladding layer before and after substrate preheating. (a) Unheated substrate;

Fig. 7. Cross-sectional microstructures of cladding layer in different regions at same depth before and after substrate preheating. (a) Observation position before substrate preheating; (a1)‒(a3) microstructures at different positions before substrate preheating; (b) observation position after substrate preheating; (b1)‒(b3)microstructures at different positions after substrate preheating

Fig. 8. Longitudinal-section microstructures of cladding layer in different regions at same depth before and after substrate preheating . (a) Observation position before substrate preheating; (a1)‒(a3) microstructures at different positions before substrate preheating; (b) observation position after substrate preheating; (b1)‒(b3)microstructures at different positions after substrate preheating

Fig. 9. XRD patterns of cladding layers before and after substrate preheating

Fig. 10. EDS line scanning results of cladding layer. (a) Line scanning position before substrate preheating; (b) elemental distribution before substrate preheating; (c) line scanning position after substrate preheating; (d) elemental distribution after substrate preheating

Fig. 11. Phase diagram of Fe-Cr-C ternary alloy^［28］

Fig. 12. Contour plots of surface microhardness of cladding layer before and after substrate preheating . (a) Schematic of hardness test; (b) microhardness before substrate preheating ; (c) microhardness after substrate preheating

Fig. 13. Temperature distributions of cladding layer before and after substrate preheating. (a) Surface before substrate preheating;

Fig. 14. Node temperature curves. (a) Schematic of node locations; (b) temperature curve

Fig. 15. Temperature field simulation experiment. (a) Measurement temperature position of thermocouple; (b) temperature versus time

Fig. 16. Residual stress change on path 1 before and after substrate preheating. (a) Schematic of path 1; (b) residual stress change

Fig. 17. Residual stress change on path 2 before and after substrate preheating. (a) Schematic of path 2; (b) residual stress change