Post-build hot iso-static pressing (HIP) has become a common practice for the closure of some types of defects in AM metal components. Assuming your products lend themselves to HIPing, can this post-processing method get rid of all porosity?
- Processing: parameters and/or and inhomogeneous powder feeding generate key hole effect and/or lack of consolidation;
- Solidification kinetics and post-heat treatment homogenisation: this depends on the feedstock composition;
- Feedstock contamination: oxidation and hydrogenation promote physi-adsorption and chemi-adsorption during phase change, where gases are released and trapped in the material;
- Feedstock properties: internal pores present in powder particles, particles features induce non-homogeneous feedstock behaviour, e.g. variable spreadability;
Impact of HIP on gaseous pores present in virgin powder particles and surviving processing
It is important to point out that it is impossible to achieve actual full densification in powders provided that entrapped gas pores were present .
 Cunningham, Narra, Montgomery, Beuth, and Rollett, 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 2017, DOI: 10.1007/s11837-016-2234-1
 B. H. RABIN et al., Characterization of Entrapped Gases in Rapidly Solidified Powders, Materials Science and Engineering, A 124 (1990) 1-7
 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