Direct Laser Sintering of metal parts: characterisation and evaluation of joining mechanisms

Rapid Prototyping and Tooling are playing a more and more important role in the achievement of compressed time-to-market solutions, where prototype parts and tools are produced directly from the CAD model [1- 8]. In particular, Selective Laser Sintering (SLS) of metal powders with liquid phase is frequently applied for the production of inserts for injection moulding of plastic parts.On the basis of the deep knowledge developed by the authors on the solid-state process [1-4], an experimental campaign has been planned to investigate the surface finish and mechanical performances of Direct Laser Sintering technique. In particular, the research objective was to evaluate the effect of the laser sintering strategy on the anisotropy of the final part. Tensile specimens of DirectMetal 20 and DirectSteel 20 materials have been produced, following the specifications of standard ASTM E8, with different orientations in regard to laser path. Rupture surfaces after the tensile tests were observed at the SEM, in order to understand failure mechanisms, whereas the observation of polished sections helped investigating joining phenomena between the particles. The proposed experimental methodology allowed correlating the macroscopic performances to the micro-mechanisms ruling the process, proving that no considerable differences can be noticed between samples produced in the X and Y direction within the plane of powder deposition.