Trapped Powder Removal from Sheet-Based Porous Structures Based on Triply Periodic Minimal Surfaces Fabricated by Electron Beam Powder Bed Fusion

Abstract

Electron Beam Powder Bed Fusion-manufactured (E-PBF) porous components with narrow pores or channels and rough walls or struts can be filled with trapped powder after the manufacturing process. Adequate powder removal procedures are required, especially for high-density porous structures. In the present research, sheet-based porous structures with different thicknesses based on triply periodic minimal surfaces fabricated by E-PBF were subjected to different post-processing methods, including a traditional powder recovery system for E-PBF, chemical etching and ultrasound vibration-assisted powder removal. Wall thickness, internal defects, microstructure and morphology features, powder distribution inside specimens, mechanical properties and deformation modes were investigated. A powder recovery system cannot remove all residual powder from dense structures. In turn, chemical etching can provide better powder removal but may modify the surface morphology and affect the wall thickness, considerably influencing the mechanical properties of the whole structure. The ultrasound vibration method allows for the removal of residual powder from dense structures without a severe degradation of mechanical properties. Ultrasound vibration caused grain refinement that followed from grain size aspect ratio raise from 0.35 to 0.41 µm and average grain size reduction from 1.25 to 1.02 µm.

Keywords: Additive manufacturing, residual power removal, Ti6Al4V alloy, TPMS structures, Electron Beam Powder Bed Fusion