In a selective laser melting process, it is common to reuse the powder in consecutive cycles of the route because it is more sustainable and cost effective. However, it is unknown whether reusing the material has an influence on the process. In this paper, Inconel 718, Ti6Al4V, AlSi10Mg and Scalmalloy are characterized to determine the impact of reusing powders on the additive manufacturing (AM) process under an argon high-purity atmosphere. Virgin powders were taken from the suppliers and compared to powders that had been used in the process for a long period of time with periodic 'rejuvenation'. A well-structured characterization procedure, combining many existing techniques, is proposed, determining changes in the morphology, composition (chemical and microstructure) and flowability. Clear differences between the virgin and used state are revealed by the characterizations; AlSi10Mg, appears to be the most sensitive to reuse with changes in particle size distribution and morphology, and with an increase in the oxygen content. The main contribution of this paper is providing insight into the effects of reuse for four commonly used AM powders, by means of a simple but well-structured method that links the particle feature characterization process to the flowability of metal AM powders. The provided insights enable enhanced decision-making on recycling and reuse of powder for specific AM processes.
Laser-based additive manufacturing (LBAM) is a versatile manufacturing technique, extensively adopted to fabricate metallic components of enhanced properties. The current review paper provides a critical assessment of the fabricated metallic coatings and parts through LBAM-processes [e.g., laser metal deposition (LMD) and selective laser melting (SLM)] for high temperature tribological applications. A succinct comparison of LBAM-fabrication and conventional manufacturing is given. The review provides an insight into the sophisticated application-driven material design for high temperature tribological contacts. The review highlights the major mechanisms behind the improvement in the tribology of the laser-deposits; properties evolving as a consequence of the microstructure, lamellar solid lubricants, sulfides, soft metals, lubricious oxides, and self-lubricating surfaces.
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