Mitigating Inherent Micro-Cracking in Laser Additively Manufactured René 108 Thin-Wall Components

• DOI: 10.2139/ssrn.4150319
• Publication Date: 2022-07-01T12:14:10Z
• Authors: Apratim Chakraborty; Reza Tangestani; Khadijeh Esmati; Trevor Sabiston; Lang Yuan; Étienne Martin
• Keywords: 0203 mechanical engineering; 02 engineering and technology; 0210 nano-technology

Thin-wall components made of a hard-to-weld Ni-based superalloy, RENÉ 108, are fabricated using the laser powder bed fusion (LPBF) additive manufacturing (AM) technique. Thirty-two parts, including ten different scan strategies and four wall thicknesses (WTs) between 0.25 mm 1.00 mm, studied compared with conventional continuous 67° rotation (Cont.) strategy. Microstructure characterization shows micro-cracks aligned build direction (BD) melt-pool boundaries. All exhibit inter-dendritic morphologies in vicinity cracked boundaries, suggesting solidification cracking mechanism. Larger WTs more susceptible to micro-cracking, supported by earlier transition positive stress triaxiality states through finite element modelling (FEM). Similarly, increasing (vector) lengths generates higher micro-crack densities. Beam-scale FEM predicts in-process stresses perpendicular growth directions, promoting micro-cracking processed longer vector (VLs). Parts alternating inter-layer strategies. Scan rotations reduce propensities 12-62% zero due homogeneous distribution during progression. Furthermore, short VLs create 50-70% fewer than long beneficial Cont. strategy reduced along direction.