Mitigating inherent micro-cracking in laser additively manufactured RENÉ 108 thin-wall components. (March 2023)

• Record Type: Journal Article
• Authors: Chakraborty, Apratim; Tangestani, Reza; Esmati, Khadijeh; Sabiston, Trevor; Yuan, Lang; Martin, Étienne
• Is Part Of: Thin-walled structures. Volume 184(2023)
• Publication Date: 2023-03
• Subjects: Additive manufacturing -- Laser powder bed fusion -- Thin-wall -- Scan strategy -- Superalloys -- Cracking; Thin-walled structures -- Periodicals; 690.1
• DOI: 10.1016/j.tws.2022.110514
• Languages: English
• ISSNs: 0263-8231

Abstract

Abstract: Thin-wall components made of a hard-to-weld Ni-based superalloy, RENÉ 108, are fabricated using laser powder bed fusion. Thirty-two parts, including ten different scan strategies and four different wall thicknesses between 0.25 mm and 1.00 mm, are studied and compared with the conventional continuous 67° scan rotation strategy. Microstructure characterization shows micro-cracks aligned with the build direction and melt-pool boundaries. All micro-cracks exhibit inter-dendritic morphologies in the vicinity of the cracked boundaries, suggesting a solidification cracking mechanism. Thicker parts and long vector length are more susceptible to micro-cracking due to earlier transition to positive stress triaxiality states demonstrated through finite element modeling.​ Parts are processed with alternating and continuous inter-layer scan rotation strategies. Scan rotations reduce micro-cracking propensities by 12%–62% compared to zero scan rotations due to more homogeneous stress distribution during build progression. Furthermore, alternating long vector lengths create 100%–230% more micro-cracks than alternating short vector lengths, which are more beneficial than the 67° continuous rotation strategy due to reduced in-process stresses. Shorter vector lengths with interlayer scan rotations are optimal for micro-crack mitigation. Graphical abstract: Highlights: Thirty-two thin-wall parts built to study micro-cracking in additive manufacturing. Micro-cracking propensities lower for thinner walls and shorter scan vectors. Earlier transition and higher positive stress triaxiality state promote micro-cracking. Scan rotations reduce micro-cracking by 12%–62% due to stress homogenization. Alternating short scan rotations beneficial for thin-wall micro-crack mitigation.