Recycling Of Spent Powders From Additive Manufacturing Processing Of Inconel 625 For The Synthesis Of Cocrfenimoxnb0.4x (X=0-0.1) Multi-Principal Element Alloys (Mpeas) By Spark Plasma Sintering (SPS) Of Mechanically Alloyed Powders

Sieve residues from the powder recycling stream in Laser powder bed fusion (L-PBF) processing of Inconel 625 are currently disposed of as hazardous waste, which conflicts with circular economy thinking. Here, the synthesis of metal matrix composites (MMCs) based on carbide- and oxide-strengthening phases finely dispersed in a Multi-Principal Element Alloy (MPEA) matrix was explored as a recycling option for these powders. In particular, mixtures of virgin metal powders and a spent Inconel 625 powder were mechanical alloyed and consolidated by Spark Plasma Sintering (SPS). The process control agent (PCA, ethanol) used during mechanical alloying acted as a source for C and O in the subsequent crystallization of nano-sized carbides and oxides during sintering. By carefully controlling the powder mixture composition, MPEA matrices with different contents of Nb and Mo in the face-centered cubic structure were obtained, as revealed by X-ray Powder diffraction. The bulk samples were further characterized by Scanning Electron Microscopy (SEM) and preliminary mechanical analyses using instrumented indentation. The results showed that spent powder of Inconel 625 was a valuable source of 4d transition metals for the synthesis of MMCs based on a MPEA matrix with enhanced solid solution strengthening and finely dispersed ceramic phases.