A normalized enthalpy framework for process-window scaling in laser powder bed fusion of IN738LC: From single track to bulk
Optics and Laser Technology, cilt.204, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 204
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.optlastec.2026.116437
- Dergi Adı: Optics and Laser Technology
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Applied Science & Technology Source, Compendex, INSPEC, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO)
- Anahtar Kelimeler: Effective laser absorptivity, IN738LC superalloy, Laser powder bed fusion, Melt pool geometry, Normalized enthalpy, Process mapping
- Gazi Üniversitesi Adresli: Evet
Özet
Laser powder bed fusion (LPBF) of crack-prone, γ′-strengthened nickel-based superalloys such as IN738LC requires physically based strategies for scaling process windows from single tracks to bulk builds. This study applies a normalized enthalpy (NE) framework to 23 power–speed combinations produced on an EOS M290 (P= 150 W to 350 W; v = 0.28 m s−1 to 2.22 m s−1). NE scales the absorbed laser input by the volumetric enthalpy required to heat the alloy from the build plate temperature to the liquidus temperature. The effective absorptivity η was inferred from measured melt pool width and depth and ranged from 0.57 to 0.87. The conduction–keyhole boundary was assigned at D∗=2D/W=1, corresponding by construction to NEη=Φ, where Φ=Δhvap,mol/Δhfus,mol≈8.45. Melt pool width and depth increased with calibrated NE. The arithmetic mean surface height reached a minimum near the conduction–keyhole boundary, whereas the maximum bulk density occurred at a somewhat higher NE in the stable-keyhole regime. Relative density reached 99.43% by the Archimedes method and 99.99% by X-ray computed tomography. NE overlap criteria related single-track geometry to hatch spacing selection. EBSD of three fixed-power conditions revealed a non-monotonic texture response, with the highest M-index at intermediate NE and weaker texture at the highest NE. The results show that geometry-based absorptivity calibrated NE provides an alloy-specific framework for organizing single track and bulk build behavior, while remaining dependent on the calibrated geometry.