Controlling Grain Growth in Powder Bed Fusion of Yttria‐Stabilized Zirconia Using Femtosecond Lasers: Challenges and Methodological Insights

Abstract

This study demonstrates binder‐free laser powder bed fusion (PBF‐LB) of 8 mol% yttria‐stabilized zirconia (8YSZ) using a femtosecond laser and a triangular scan strategy that controls heat accumulation by varying scan‐vector length. Laser power (31–52 W), scan speed (100–500 mm s −1 ), defocus (+2 to +14 mm), and pulse repetition rate (0.5–32 MHz) were screened. Surface homogeneity was evaluated by a Canny‐based Surface Pixel Score, grain‐size distributions were quantified from SEM micrographs using kernel‐density statistics from more than 4,000 grains, and thermal behavior was analyzed by infrared thermography supported by finite‐difference simulations. The optimum parameter set (52 W, 400 mm s −1 , +12 mm defocus, 2 MHz) produced the largest continuous vitrified region. Thermography revealed thermal regimes and abrupt temperature jumps near scan‐vector lengths of 7 and 17 mm, indicating changes in heat accumulation consistent with high‐temperature densification and localized melting. Simulations reproduced the position and qualitative form of these signatures. Rectangular scans confirmed scan‐speed‐dependent grain refinement, reducing mean grain size from 51.8 µm at 200 mm s −1 to 40.3 µm at 500 mm s −1 . The results establish an additive‐free route toward vitrified, fine‐grained 8YSZ layers.