A B S T R A C TThe possibility to reuse the metal powder wasted in Laser Material Deposition (LMD) process has been evaluated and a simple procedure developed. LMD uses metal powder which is fed through a nozzle into the focal point of a laser, where it melts the powder and the substrate material. During the process, a high ratio of particles hits against an unmelted area and directly bounces off the deposited area. The efficiency ratio of deposition can drop to 40% depending on the configuration and spot size. This work deals with the design of a procedure to recollect and reuse the wasted powder of a nickel based superalloy IN718. After usage, powder is recollected, undesired fractions are magnetically segregated and aggregates are removed by sieving. The particles are mixed again and ready for reuse. In order to study the effectiveness of the process, no new powder has been added to the recovered fraction, and this procedure has been repeated five times. Experimental tests show that deposited material present similar properties than those obtained with new powder grains. But, after 3 reuses, the porosity content increases consequently and the rupture strain decreases strongly. The implementation of this process allows the improvement of the final efficiency, reducing costs and decreasing the hazardous powder amount.
In recent years, many researchers have attempted to model the solidification process of nano-reinforced materials. In the present document, the effect on the heterogeneous solidification regime of the different sizes, shapes, and chemical compositions of nanometric ceramic particles in an AlSi10MnMg alloy is studied. This article develops a mathematical model to predict the solidification behavior of a general nano-reinforced alloy, then validates the results using experimental techniques. The main objective of the model is to minimize the costly and time-consuming experimental process of fabricating nano-reinforced alloys. The proposed model predicts the critical Gibbs energy and the critical radius required for nucleation in the heterogeneous solidification regime. Conversely, the experimental part focuses on understanding the solidification process from the differential thermal analysis (DTA) of the solidification curves. It was concluded that if subcooling is involved, cubic and pyramidal particles work better as nucleating particles in the studied alloy.
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