Fig. 1. Gas-atomized ZGH451 nickel-based superalloy powder. (a) Particle morphology; (b) particle size distribution

Fig. 2. Forming ZGH451 nickel-based superalloy by LPBF. (a) Laser scanning strategy; (b) size of tensile specimen; (c) formed samples

Fig. 3. Variation curves of relative density of ZGH451 alloy formed by LPBF with scanning speed and scanning spacing under different laser powers. (a) 200 W; (b) 150 W

Fig. 4. Process window and metallurgical defect feature maps of typical samples at laser power of 200 W

Fig. 5. Process window and metallurgical defect feature maps of typical samples at laser power of 150 W

Fig. 6. Typical distribution characteristics of cracks in ZGH451 superalloy formed by LPBF. (a) SEM image; (b) local magnification of Fig. 6 (a); (c) EBSD grain orientation distribution; (d) grain angle difference on both sides of crack

Fig. 7. SEM images of typical samples of crack-free and high-density ZGH451 superalloy formed by LPBF. (a) Overall morphology of microstructure; (b) coarsened dendrites at bottom of molten track; (c) precipitates between dendrites; (d) different oriented dendrites at edge of molten track

Fig. 8. Analysis of precipitated phase characteristics of crack-free and high-density ZGH451 superalloy samples formed by LPBF. (a) TEM dark field image; (b) EDX element surface distribution; (c) HR-TEM image and electron diffraction spot diagram

Fig. 9. EBSD maps of crack-free and high-density ZGH451 superalloy samples formed by LPBF at different positions. (a) Inverse pole figure (IPF) of grain morphology and orientation characteristics at bottom; (b) IPF of grain morphology and orientation characteristics at middle; (c) IPF of grain morphology and orientation characteristics at top; (d) pole figure of {001} characteristic crystal plane at bottom; (e) pole figure of {001} characteristic crystal plane at middle; (f) pole figure of {001} characteristic crystal plane at top

Fig. 10. SEM images of tensile fractures of crack-free and high-density ZGH451 formed by LPBF

Table 1. Nominal chemical compositions of ZGH451 nickel-based superalloy (mass fraction, %)

Table 2. Parameters for LPBF experiment

Table 3. Comparison of yield strength between ZGH451 formed by LPBF superalloy and other single crystal superalloys^[35-36]