Optimum deposition parameters for the direct laser fabrication (DLF)
of quasi-hollow structures

Abstract. Analytical and numerical procedures have been conducted in order to predict optimum deposition parameters for the fabrication of quasi hollow metallic structures using direct laser fabrication (DLF). Using a 3 axis system, the deposition of stainless steel powders 316L and 304L onto a mild steel substrate was carried out using a CO2 CW 1.5kW laser. The structures built comprise of both vertically built walls and walls built at an angle to the vertical. This combination of builds allows parts with internal voids to be fabricated that would otherwise be extremely difficult to build using conventional manufacturing techniques. The mathematical model is used to predict the best clad cross-section shape that will promote multiple-layer builds at different angles of inclination. Temperature distribution results obtained using the ABAQUS FE package are used to investigate melt pool characteristics and help predict microstructure evolution. A number of samples were deposited using varying process parameter combinations and sectioned to investigate the effect of clad shape and microstructures formed. During the deposition, readings from thermocouples placed around the build were used to verify the reliability of the ABAQUS numerical model. The results from the two approaches combined give a series of process parameters suitable for depositing such novel structures.

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