Permeable Additive Manufacturing Qualification Framework and Evaluation Methodology for Inconel 718

Abstract Permeable additive manufacturing is immature relative to the field of additive manufacturing, resulting in unknown operating margins for end-use applications. Permeable additive structures are commonly manufactured via Laser Powder Bed Fusion through varying weld penetrations and hatch spacing. These methods produce permeable structures with unique manufacturability, mechanical properties, and flow resistances. Preliminary results of this work confirm correlations of porosity and permeability. The correlation of porosity and permeability is agnostic to the exact structural composition of the printed material, which may mask flaws beneath the surface of the build. While target permeability can be met for a given porosity, the equivalent pore volume can include large, inconsistently located voids instead of an equivalent volume of smaller, evenly spaced pores. To rephrase, select build parameters may cause internal part delamination that are only visible after metallographic cross-section examination. The delamination inherently reduces mechanical properties that are needed for end-use applications and must be avoided. The previous literature has provided quality overviews of permeable additive manufacturing and point design applications but lacks information on the full scope of manufacturing failure mechanisms. This manuscript expands upon mainstream literature, providing failure mechanisms and performance correlations to develop a holistic view of laser parameter development for permeable additive manufacturing. In short, this work provides detailed manufacturing guidelines, inclusive of post-processing techniques, as well as an evaluation methodology to correlate build parameters to performance parameters for Inconel 718.