Localized Energy Absorption through LaB₆ Surface Modification of PA12 Enables Enhanced Tensile Performance in Diode Laser PBF‐LB

The shift to energy‐efficient near‐infrared (NIR) diode lasers in polymer powder bed fusion (PBF‐LB/P) challenges standard polymer powders due to insufficient NIR absorption and necessitates tailored feedstock modifications. This study explores the potential of surface modification (s‐mod) of polyamide 12 (PA12) with LaB 6 nanoparticles (NP) as a scalable alternative to conventional volume modification (v‐mod) with carbon black (CB). Despite a tenfold lower overall NIR absorbance, s‐mod PA12 achieves comparable melting behavior with only a 1.5‐fold increase in laser energy. Combined differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) analyses reveal that surface‐localized absorption enables partial retention of α ‐domains at intermediate energy densities, consistent with a heterogeneous, surface‐dominated melting mechanism. At higher energies, s‐mod and v‐mod converge to fully γ ‐phase materials with comparable crystallinity. Mechanical testing demonstrates that intermediate s‐mod parts exhibit higher crystallinity, whereas fully molten s‐mod parts outperform v‐mod counterparts in tensile strength while maintaining ductility. Our findings indicate that s‐mod PA12 not only matches the processability of industrial v‐mod powders but also introduces new degrees of freedom for tailoring mechanical properties via controlled melting. Decoupling energy absorption from volumetric filler loading expands the material design space for NIR‐based additive manufacturing and paving the way for next‐generation, high‐performance polymer components.