The effect of powder recycling in direct metal laser deposition on powder and manufactured part characteristics

A potential way of improving the material efficiency and cost effectiveness of the Direct Metal Laser Deposition (DMLD) process is to take powder that is not utilised in each deposition attempt and re-use it in subsequent attempts (powder recycling). Currently, this is not widely implemented for fear of a detrimental effect on part quality. This study examines how powder recycling, using simple normalisation techniques, affects the powder and the quality of the deposited part. Work was conducted on commercially available DMLD equipment with gas-atomised Waspaloy powder. Powder characteristics such as morphology, size distribution, and purity, and deposited part characteristics such as microstructure and mechanical properties, were quantified for 10 deposition – normalisation - re-use cycles. The use of normalised powder resulted in successful deposition over all 10 re-cycle stages and did not appear to compromise part integrity. Properties and microstructure, while not completely uniform throughout the 10 cycles, did not vary by large amounts. The powder showed greater variation in size distribution and composition with increasing re-cycle stages. Variations throughout the process, their causes, and the potential benefits of the normalisation procedure used are discussed