Author Affiliations
1School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China2Shanghai Space Propulsion Technology Research Institute, Shanghai 201100, Chinashow less
Fig. 1. Microstructures of 30Cr3 base metal. (a) Optical and confocal images; (b) SEM image; (c) IPF; (d) EDS plane distribution of Cr element
Fig. 2. Schematics of test devices. (a) Observing dynamic behavior of molten pool; (b) observing dynamic behavior of keyhole
Fig. 3. Dynamic behaviors of keyholes under different weld penetration modes. (a1)-(a5) Keyhole unpenetrated fusion mode; (b1)-(b5) keyhole critical penetration fusion mode; (c1)-(c5) keyhole stably penetrated fusion mode
Fig. 4. High speed photographic images of molten pool during welding process under different laser powers. (a) 3.4 kW; (b) 3.5 kW; (c) 3.6 kW; (d) 3.7 kW
Fig. 5. Average amplitudes and standard variances of molten pool surface vibrations under different laser powers
Fig. 6. Cross section morphologies and sizes of welded joints under different laser powers. (a)(d) 3.4 kW, morphology; (b)(e) 3.5 kW, morphology; (c)(f) 3.6 kW, morphology; (g) size
Fig. 7. Morphologies of rear welds under different laser powers. (a)(e) 3.4 kW; (b)(f) 3.5 kW; (c)(g) 3.6 kW; (d)(h) 3.7 kW
Fig. 8. Microstructure of weld. (a) SEM image of weld microstructure; (b) partial magnification view of Fig. 8(a)
Fig. 9. EBSD analysis results of weld microstructures under different laser powers. (a)(e)(i) 3.4 kW; (b)(f)(j) 3.5 kW; (c)(g)(k) 3.6 kW; (d)(h)(l) 3.7 kW
Fig. 10. XRD analysis results of weld microstructures under different laser powers. (a) XRD patterns; (b) partial magnification view of Fig. 10(a); (c) SEM image of metallic oxide
Fig. 11. Tensile properties of welded joints under different laser powers. (a) Without heat treatment; (b) with post-weld heat treatment
Fig. 12. Fracture locations and fracture morphologies of tensile samples. (a)(b) Without heat treatment; (c)(d) after post-weld heat treatment
Fig. 13. Longitudinal microhardness distributions of welded joints under different laser powers. (a) 3.4 kW; (b) 3.5 kW; (c) 3.6 kW; (d) 3.7 kW
Chemical composition | C | Cr | Si | Ni | Mo | V | Mn | Fe | CE |
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Mass fraction /% | 0.295 | 2.982 | 1.081 | 1.051 | 0.940 | 0.103 | 0.702 | Bal. | 1.32 |
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Table 1. Chemical compositions of 30Cr3 ultra-high strength steel
Laser power | Absorbed energy /J | Standard deviation /J | Estimated value for standard impact samples /J |
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Base material | 18.70 | - | 74.80 | 3.4 kW | 10.41 | 1.74 | 41.64 | 3.5 kW | 9.23 | 2.13 | 36.92 | 3.6 kW | 14.36 | 0.86 | 57.44 | 3.7 kW | 13.92 | 0.93 | 55.68 |
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Table 2. Impact test results under different laser powers