Effect of energy density on cracking of ZGH451 superalloy by laser powder bed fusion

ZGH451 is a novel age-strengthened nickel-based superalloy renowned for its exceptional toughness and corrosion resistance. However, it is susceptible to cracking during laser powder bed fusion (LPBF) processing. This study systematically investigates LPBF-fabricated ZGH451 to establish the inherent relationship between volumetric energy density (VED) and crack evolution, with particular emphasis on crack initiation and propagation mechanisms. Our findings confirm that optimized VED effectively suppresses cracking. Experimental results reveal that VEDs above 70 J/mm 3 induce edge-localized cracks dominated by stress cracks and ductility-dip cracks (DDC), whereas VEDs below 45 J/mm 3 produce surface-distributed fine cracks characterized as solidification/liquation cracks. Microstructural analysis demonstrates two distinct mechanisms: excessive VED facilitates high-angle grain boundary cracking, while Al/Ti-based low-melting eutectic phases and Cr/W/Ta/C-derived carbides synergistically enhance grain boundary embrittlement, thereby creating prerequisites for crack nucleation and growth. Moreover, by adjusting the VED from 100 J/mm 3 to 49.45 J/mm 3 , the grain size is refined from 62.43 µm to 35.83 µm, and the grain boundary density is increased by 42.6 %. These improvements significantly reduce stress concentrations and crack formation. This work establishes fundamental correlations between VED and crack behavior in LPBF-processed ZGH451, providing critical guidance for defect mitigation through controlled energy parameters.