Experimental investigation on Laser Directed Energy Deposition based additive manufacturing of Al2O3 bulk structures

Abstract In the present study, the effect of various processing parameters is investigated for building Al2O3 ceramic structures by laser additive manufacturing using the direct energy deposition technique (LAM-DED). The study shows that uniform single tracks and three dimensional (3D) structures of Al2O3 can be fabricated on alumina and Ti–6Al–4V substrates at the laser power of ~225 and ~300 W, respectively, for a fixed scanning strategy (θ = 0°), feed rate (8 g min−1) and scanning speed (0.6 m min−1). Optical microscopy, synchrotron-based X-ray micro-computed tomography (SR-μCT) examination and density measurement reveals that the bulk Al2O3 structures built on Ti–6Al–4V substrate have lower defects (porosity and cracks) and higher relative density (RD) = 85% than that fabricated on the alumina substrate (RD = 70%). This is primarily attributed to uniform melt pool formation on Ti–6Al–4V substrate at higher laser power. In addition to laser power, it is also found that the thermo-physical properties of the substrate material play a vital role on melt pool formation, which in turn decides the defect structure in built bulk Al2O3 components. Further, the change in scanning strategy to 45° and 67° increases the density of bulk Al2O3 structures built on Ti–6Al–4V substrate to 90% and 95%, respectively. The SR-μCT analysis of bulk structures built with different scanning strategies on the Ti–6Al–4V substrate confirmed that scanning strategy plays a vital role in the shape, size, and distribution of pores that formed during LAM-DED process. The study paves a way for LAM-DED of Al2O3 bulk structures by deriving the advantage of scan strategy and optimized processing parameters.