  We investigate the hot cracking susceptibility and creep resistance of three
versions of a nickel-based superalloy with different contents of boron, carbon
and zirconium fabricated by laser powder bed fusion. Crack-free and creep
resistant components are achieved for alloys with boron, carbon and no
zirconium. We then rationalize this result by evaluating how boron, carbon and
zirconium are distributed at grain boundaries in the as-built and heat-treated
microstructures of an alloy containing all these elements. Observations are
conducted by scanning and transmission electron microscopy, and atom probe
tomography. In the as-built microstructure, boron, carbon and zirconium
segregate at high-angle grain boundaries as a result of solute partitioning to
the liquid and limited solid-state diffusion during solidification and cooling.
After heat-treatment, the amount of boron and carbon segregating at grain
boundaries increases significantly. In contrast, zirconium is not found at
grain boundaries but it partitions at the gamma' precipitates formed during the
heat treatment. The presence of zirconium at grain boundaries in the as-built
condition is known to be susceptible to enhance hot cracking, while its absence
in the heat-treated microstructure strongly suggests that this element has no
major effect on the creep resistance. Based on our observations, we propose
alloy design guidelines to at the same time avoid hot cracking during
fabrication and achieve the required creep performance after heat-treatment.
