# Analysis of Building Platform Inhomogeneities in PBF-LB/M Process on Alloy 718
## 4 Conclusions  
This work elucidates and quantifies the entity of the building platform inhomogeneities in the PBF-LB/M process through the evaluation of the Track's stability level and Melt Pool of several Single Tracks. Moreover, the density and defect distribution inside the material have also been measured.  
It is possible to highlight how each process parameter that was evaluated, i.e., Exposed Area (%), Position on building platform, and Differential Pressure, has a main effect on the building platform inhomogeneities. In particular:  
* The Exposed Area increase promotes Single Track instability, loss of conductive regime and defect formation;
* Criticality for printability of Alloy 718 in the EOS M290 machine at the position closed to the outlet nozzle and in general when the Exposed Area is more than about 50% of the build platform has been detected;  
Figure 18: Contour plot of melt pool width as a function of exposed area, position and differential pressure: (**a**) Low level; (**b**) Nominal level; (**c**) High level.  
* A mitigation is possible increasing the value of the Differential Pressure and thus shielding the gas flow velocity, facilitating the removal of the melting's subproducts, such as spatter particles;
* The interaction between the parameters is quite low or null, allowing us to optimize each one without having any effect on the other.  
In conclusion, this investigation remarks on some criticality for the printability of Allot 718 in the EOS M290 machine; the mitigation suggested by experimental results can improve the Track's and the Melt Pool's stability, allowing the manufacture of a defect-free and fully dense material. The results shown allow for suggestions on how to use the printing platform during job definitions when there is a need to maximize its use.  
A critical aspect to be considered, as a result of the increased gas flow velocity, could be a partial denudation of the powder in the building platform area near to the gas flow nozzle inlet. In future work, this critical aspect will be investigated in order to evaluate the robustness of the proposed mitigation solution on printability inhomogeneities on the PBF-LB/M process.  
Conceptualization, N.B., L.C., M.P., A.G. and P.C.; methodology, L.C., M.M., A.G. and M.P.; software, N.B., L.C. and M.M.; validation, M.M. and M.P.; formal analysis, N.B., L.C., and A.G.; investigation, N.B., L.C. and A.G.; resources, M.P.; data curation, N.B., M.M. and A.G.; writing--original draft preparation, N.B., L.C. and A.G.; writing--review and editing, N.B., L.C., M.M., A.G., G.A. and P.C.; visualization, N.B., L.C. and A.G.; supervision, M.P., A.G. and P.C.; project administration, M.P.; funding acquisition, M.P. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
**Data Availability Statement:** Summarized data are contained within the article. The raw data are available on request from the corresponding author after obtaining the permission of Baker Hughes, Nuovo Pignone.  
Authors [PERSON], [PERSON], [PERSON], and [PERSON] were employed by the company Baker Hughes, Nuovo Pignone. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.