Effect of processing parameters on surface roughness, porosity and cracking of as-built IN738LC parts fabricated by laser powder bed fusion

• Published in: Journal of materials processing technology 2020-11, Vol.285, p.116788, Article 116788
• Main Authors: Guo, Chuan, Li, Sheng, Shi, Shi, Li, Xinggang, Hu, Xiaogang, Zhu, Qiang, Ward, R. Mark
• Format: Article
• Language: English
• Subjects: Computed tomography; Crack density; Flux density; Laser powder bed fusion; Lasers; Marangoni convection; Melting; Nickel base alloys; Nickel-Based superalloy; Porosity; Powder beds; Process parameters; Processing parameters; Rapid prototyping; Regression analysis; Residual stress; Solidification; Superalloys; Surface properties; Surface roughness
• ISSN: 0924-0136; 1873-4774
• DOI: 10.1016/j.jmatprotec.2020.116788

•Processing parameters have significant effect on printing qualities during LPBF.•Rayleigh instability and Marangoni convection can deteriorate the surface quality.•Pores are caused by lack of fusion and keyhole regarding to different VEDs.•Residual stress and solidification time affect crack density related to parameters.•VED of ∼ 48 J/mm3 is optimal for building IN738LC components by LPBF. An investigation was conducted to understand how different parameters, namely laser power, scan speed and hatch spacing, influence the printing qualities, i.e. surface roughness, porosity and crack density of the nickel-based superalloy Inconel 738LC during laser powder bed fusion. Insufficient overlap, Plateau–Rayleigh instability and Marangoni convection were identified and characterized as the factors that could deteriorate the surface quality of as-built IN738LC parts. Two leading causes of pore were determined by metallographic analysis and computed tomography as lack of fusion and keyhole, which were attributed to different energy input densities. Crack density was measured by metallographic observation. Residual stress and the time for solidification of melt were identified as the key factors that affected the crack density. Finally, the relationships between the printing qualities and volume energy density were established by regression analysis, and the VED of ∼ 48 J/mm3 was optimal for fabricating IN738LC in the LPBF process