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. This master thesis will focus primarily on experimental work in the PBF-EB printer. Samples will be characterized before and after HIP to determine process stability, shell integrity, density, pore morphology, microstructure, and dimensional change. 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 outcomesA 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. A successful thesis is expected to prioritize robust PBF-EB processing, verification of shell airtightness, reliable HIP densification, and accurate shrinkage measurements. 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). 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). 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] ****

[2] Whitepaper | HIP for Free: Speed Printing Unleashed