Fig. 1. Schematic of N₂-supplied protective hollow beam deposition nozzle

Fig. 2. Model and data processing. (a) Hollow sphere model and its quarter section; (b) horizontal dislocation stratification method; (c) normal stratification method

Fig. 3. Continuous multi-position LMD process. (a) LMD experimental design; (b) three posture forming design

Fig. 4. Stages ① of the deposition process. (a) Experimental design; (b) mechanical model of the molten pool; (c) experimental process

Fig. 5. Stages ② of the deposition process. (a) Experimental design; (b) mechanical model of the molten pool; (c) experimental process

Fig. 6. Stages ③ of the deposition process. (a) Experimental design; (b) mechanical model of the molten pool

Fig. 7. LMD forming of hollow sphere. (a) Hollow sphere at stage ③; (b) final closed deposition; (c) surface remelting

Fig. 8. Hollow sphere size. (a) Half-section of model; (b) formed part cut along the center line

Fig. 9. Curves of outer radius and thickness of the as-deposited hollow sphere with deposition angle α

Fig. 10. Microstructure of the as-deposited hollow sphere change with deposition angle α

Fig. 11. Curves of grain size and micro-hardness of the as-deposited hollow sphere with deposition angle α. (a) Grain size; (b) micro-hardness

Fig. 12. Hollow sphere fabricated by LMD. (a) Typical surface 3D topography; (b) curve of surface roughness with deposition angle α

Fig. 13. Hollow sphere fabricated by LMD. (a) Surface re-melting; (b) roughness line profile of re-melting surface