<p>This study aimed to reduce the cracking tendency of ZGH451 nickel-based superalloy printed by laser powder bed fusion (LPBF) by adding 1.5wt% hafnium element (Hf) to the alloy. The effects of Hf addition on microstructure, crack susceptibility, and mechanical properties were investigated through material characterizations and solidification calculations‌. The results indicate that despite a slight increase in the solidification range caused by 1.5 wt% Hf addition, the crack susceptibility of LPBF-printed ZGH451 was effectively reduced through the following three mechanisms: (1) 1.5 wt% Hf addition increased the liquid content during the final stage of solidification, thereby enhancing crack healing ability; (2) 1.5 wt% Hf addition promoted the morphology transformation of interdendritic precipitates from nearly continuous rod-shaped to discontinuous granular form, thereby enhancing the connectivity of interdendritic liquid phase during the final stage of solidification; (3) 1.5 wt% Hf addition reduced the proportion of high-angle grain boundaries, thereby decreasing the adverse effect of high-angle grain boundaries on the local solidification temperature range‌. The addition of 1.5% Hf to ZGH451 significantly expands the crack-free printing process window while maintaining high tensile strength and moderate elongation compared to conventional nickel-based superalloys.‌</p>