Some defects found in parts built using AM are related to processing parameters or to the composition of alloys optimised for more conventional, slow-cooling manufacturing process. These defects – such as porosity or cracking – can sometimes be healed by post-processing such as hot isostatic pressing (HIP). Yet, the formation of pores during AM is also linked to the quality of virgin powder.
Internal porosity in powder particles
Surface satellites on powder particles
Satellites welded to nearly-spherical particles can prevent homogeneous powder feeding and impede homogeneous consolidation.
1 R. H. Vanstone, F. J. Rizzo and J. F. Radavich, in R. Mehrabian, B. H. Kear and M. Cohen (eds.), Proc. 2nd lnt. Conf. on Rapid Solidification Processing, Principles and Applications, Reston, VA, March 23-26, 1980, Claitor's Publishing Division, Baton Rouge, LA, 1980, pp. 260-272.
2 T. Tokarz and J. F. Radavich, Microstruct. Sci., 10 (1982) 51-56.
3 Y. F. Ternovoi et al., Sov. Powder Metall. Met. Cerarn., 24 (1) (1985) 10-13.
4 U. Backmark, N. Backstrom and L. Arnberg, Powder Metall. Int., 18 (6) (1986) 422-424.
5 J. E. Flinn, G. E. Korth and R. N. Wright, in P. W. Lee and J. H. Moll (eds.), Rapidly Solidified Materials: Properties and Processing, American Society for Metals, Metals Park, OH, 1988, pp. 153-162.
6 J. Prybylowski, R. M. Pelloux and P. Price, Powder Metall., 24(2) (1984) 107-111.
7 G. I. Parabina et al., Sov. Powder Metall. Met. Ceram., 16 (7) (1977) 560-561.
8 J. E. Flinn, G. E. Korth and R. N. Wright, in F. H. Froes and S.J. Savage (eds.), Processing of Structural Metals by Rapid Solidification, American Society for Metals, Metals Park, OH, 1987, pp. 459-467.
9 J.C. Bae et al., Scr. Metall., 22(1988)691-696.
10. R. Cunningham, S.P. Narra, C. Montgomery, J. Beuth, A.D. Rollet, Synchrotron based X-ray microtomography characterization of the effect of processing variables on porosity formation in laser power-bed additive manufacturing of Ti-6Al-4V, JOM 69 (3) (2017) 479–484.
11 B. H. RABIN, G. R. SMOLIK and G. E. KORTH, Characterization of Entrapped Gases in Rapidly Solidified Powders, Materials Science and Engineering, A 124 (1990) 1-7
12 H. E. Eaton and N. S. Bornstein, Metall. Trans. A, 9 (1978) 1341-1342.
13 I.E. Anderson et al., Feedstock powder processing research needs for additive manufacturing development, Curr. Opin. Solid State Mater. Sci. (2018), https://doi.org/10.1016/j.cossms.2018.01.002
14 N. Dombrowski, W. Johns, The aerodynamic instability and disintegration of viscous liquid sheets, Chem. Eng. Sci. 18 (1963) 203–214.
15 I.E. Anderson, E.M.H. White, J.A. Tiarks, T.R. Riedemann, J.D. Regele, D.J. Byrd, R. D. Anderson, Fundamental Progress Toward Increased Powder Yields from Gas Atomization for Additive Manufacturing, in: Ryuichiro Goto, J.T. Strauss (Eds.), Advances in Powder Metallurgy and Particulate Materials-2017, Metal Powder Industries Federation, Princeton, NJ, 2017, pp. 136–146.