Master Thesis: Productivity Enhancement of PBF-EB Through Porous Printing, Stockholm

Project Description Powder Bed Fusion by Electron Beam (PBF-EB) normally aims to produce components with high density. However, productivity may be improved by creating only a gas-tight outer shell around a sintered or semi-melted porous core, followed by Hot Isostatic Pressing (HIP). In PBF-EB, internal pores are formed under vacuum, which is favorable for pore closure during HIP provided that the shell remains gas-tight. Previous studies in both PBF-EB and PBF-LB have demonstrated the feasibility of shell-core concepts, although validation for more complex geometries remains limited.[1]­,[2] If HIP is already required, the approach reduces energy input, build time, cost, and evaporation of sensitive alloying elements. The key challenges are to identify stable process parameters, verify shell integrity, and quantify porosity, densification, and dimensional shrinkage.   This master thesis will focus primarily on experimental work in the PBF-EB printer. The student will evaluate a limited set of process parameters to produce test parts with a dense shell and a porous sintered or semi-melted core. Samples will be characterized before and after HIP to determine process stability, shell integrity, density, pore morphology, microstructure, and dimensional change. The work will generate an initial dataset for shrinkage compensation and include a limited finite element modelling (FEM) task to predict and compensate shrinkage.   The aim is to determine whether a shell-core PBF-EB strategy can shorten build time while producing preforms suitable for HIP consolidation, and to establish an initial method for compensating predictable shrinkage. The scope is sized for one 30-credit master thesis: one material, simple coupon geometries, a few iterative test prints, 1-2 HIP cycles, basic sample characterization, FEM shrinkage modelling, and printing a more complex shape to evaluate the developed model and process parameters. Full constitutive model development, extensive mechanical qualification, and industrial-scale validation are outside the thesis scope. Scope and Objectives The student will:

• Review PBF-EB shell-core strategies, HIP densification, shrinkage compensation and relevant FEM approaches.
• Define a feasible specimen design with an airtight shell and a sintered and/or semi-melted core.
• Screen a small set of printer variables.
• Produce a dense reference condition and a number of shell-core conditions with varying initial density levels.
• Characterise shell integrity, density, pore morphology, dimensions, and microstructure before HIP.
• HIP and quantify densification and dimensional shrinkage.
• Create an initial shrinkage-compensation relationship based on FEM modelling.
• Estimate potential build-time and cost benefits relative to the dense reference using recorded machine data.

Expected outcomes

• A documented PBF-EB process window for manufacturing airtight shell-core structures with porous interiors.
• A dataset containing process parameters, density measurements, pore characteristics, shell integrity assessments, 3D scan dimensional measurements before and after HIP.
• Quantification of HIP-induced densification, shrinkage, and geometric deviation for selected shell-core conditions.
• A simplified FEM-based workflow for shrinkage prediction calibrated using experimental results.
• Validation of the methodology on a more complex geometry representative of practical applications.
• An optional comparison between PBF-EB and PBF-LB shell-core structures.
• An indicative assessment of productivity and cost benefits compared with conventional dense PBF-EB manufacturing.
• Recommendations for future work involving more complex geometries, wider process windows, and more advanced modelling approaches.

The student will refine the experimental matrix and FEM together with supervisors and colleagues at Swerim. A successful thesis is expected to prioritize robust PBF-EB processing, verification of shell airtightness, reliable HIP densification, and accurate shrinkage measurements. The FEM work will focus on practical shrinkage prediction and model calibration. Comparison with PBF-LB material is considered a stretch objective and will be included only if resources and project timing permit. Qualifications Master’s student in materials science, mechanical, manufacturing, aerospace engineering, applied physics, or a related field. A strong understanding of physical metallurgy and an interest in hands-on experimental work, systematic data analysis, and problem-solving are essential. Access to FEM software such as Abaqus or COMSOL through the university is required because Swerim has limited number of software licenses. Practical experience with metal powder bed fusion (PBF-EB/LB), metallurgical lab preparation, microscopy, finite element modeling (FEM), metrology, or Python/MATLAB is advantageous but not required. Project time The project is intended for a master thesis (30 credits). The planned start is January 2027, or another date agreed with the selected student. Further information This project is intended to be performed at Swerim in Stockholm. Swerim rewards the student with 50 000 SEK for an approved master thesis (30hp). For further information please contact: Emil Strandh, [email protected] Application Apply by using the application function below. The application can be written in English or Swedish. Latest date for application is 20th of November. You will receive a confirmation that Swerim has received your application. Please note that we fill the position as soon as we find a suitable applicant, which means we can fill the position before the deadline. [1] https://doi.org/10.3390/ma16165510 [2] Whitepaper | HIP for Free: Speed Printing Unleashed