Multiscale elemental segregation and post-HIP microstructural evolution in the laser powder bed fusion of IN738LC nickel-based superalloy
MATERIALS AND DESIGN, cilt.267, ss.116306, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 267
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.matdes.2026.116306
- Dergi Adı: MATERIALS AND DESIGN
- Derginin Tarandığı İndeksler: Scopus, Science Citation Index Expanded (SCI-EXPANDED), Chimica, Compendex, INSPEC, Directory of Open Access Journals
- Sayfa Sayıları: ss.116306
- Gazi Üniversitesi Adresli: Evet
Özet
Laser powder bed fusion (LPBF) of the medium-𝛾 ′ nickel-based superalloy IN738LC is strongly affected by multiscale elemental segregation, which promotes low-melting interdendritic constituents, defect sensitivity, and a heterogeneous heat-treatment response. However, the mechanistic relationship between rapid solidificationinduced segregation in the as-printed condition and subsequent post-HIP microstructural evolution remains insufficiently clarified. In this work, that link is addressed through a correlative multiscale approach combining optical profilometry, SEM/EDS, TEM, EBSD, and 𝜇XCT before and after HIP, together with velocity-dependent solidification modeling. CALPHAD equilibrium/Scheil calculations were further augmented with Aziz solute trapping to capture LPBF nonequilibrium partitioning and phase formation. Guided by this framework, a modified subsolidus–supersolvus hot isostatic pressing (SSHIP) route at 1200 ◦C, 125 MPa, for 4 h, followed by controlled cooling at 35–40 ◦C min−1, was applied. SSHIP eliminated resolvable porosity above the 6 µm XCT detection limit, reduced the nonrecrystallized fraction from 46.9% to 22.6% in the XY plane, and increased the Σ3 + Σ9 boundary fraction to 8.5% in the XZ plane without strong texture development (𝐽 ≈ 1.7–2.0). These changes were accompanied by marked improvements in yield strength, ultimate tensile strength, strain at maximum stress, and microhardness, providing a mechanistic basis for postprocessing crack-prone 𝛾 ′ -strengthened nickel-based superalloys.