Fig. 1. Microstructures of 10Ni5CrMoV steel. (a) Picture obtained by optical microscopy; (b) picture obtained by electron microscopy

Fig. 2. Schematic of experimental setup for vacuum laser welding

Fig. 3. Structure of vacuum chamber

Fig. 4. Size of tensile sample

Fig. 5. Effect of ambient pressure on penetration depth

Fig. 6. Appearance and cross-section of weld bead obtained at different ambient pressures

Fig. 7. Distribution diagram of weld bead and heat-affected zone

Fig. 8. Microstructures of weld bead obtained at different ambient pressures. (a) 105 Pa; (b) 104 Pa; (c) 103 Pa; (d) 102 Pa; (e) 10 Pa

Fig. 9. Microstructures of completed quenching zone in heat-affected zone obtained at different ambient pressures. (a) 105 Pa; (b) 104 Pa; (c) 103 Pa; (d) 102 Pa; (e) 10 Pa

Fig. 10. Microstructures of uncompleted quenching zone in heat-affected zone obtained at different ambient pressures. (a) 105 Pa; (b) 104 Pa; (c) 103 Pa; (d) 102 Pa; (e) 10 Pa

Fig. 11. Microstructures of top of weld bead obtained at different ambient pressures. (a) 105 Pa; (b) 10 Pa; (c) 105 Pa heat-affected zone; (d) 10 Pa heat-affected zone

Fig. 12. Microhardness distribution of weld bead obtained at different ambient pressures

Fig. 13. Fracture positions of weld head tensile samples obtained at different ambient pressures. (a) 105 Pa; (b) 104 Pa; (c) 103 Pa; (d) 102 Pa; (e) 10 Pa

Fig. 14. Stress-strain curves of weld bead tensile samples obtained at different ambient pressures

Fig. 15. Fracture morphology of tensile samples. (a) 105 Pa, weld zone; (b) base metal