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.
Liquid phase sintering is commonly used in powder metallurgy to improve physical properties through densification enhancement. With the aim of combining the advantages of liquid phase sintering and the use of promising alloying elements such as Mn and Si, liquid promoters with complex compositions were designed to provide a low melting point to form a liquid phase below the common sintering temperatures. The properties of these liquid phases were characterised in terms of contact angle, spreading evolution and infiltration. Using a Kru ¨ss drop shape analysis system, both wetting angle experiments and infiltration experiments were performed by changing the substrate characteristics from sintered to green iron specimens respectively. The discussion is based on the different features found for these liquids compared with copper, which is a well known liquid phase former used for improving the properties of low alloy steels. Simulations of the thermodynamic and kinetic processes taking place were performed by combining ThermoCalc and DICTRA software analysis.
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