Metal Additive Manufacturing (AM) has begun its revolution in various high value industry sectors through enabling design freedom and alleviating laborious machining operations during the production of geometrically complex components. The use of powder bed fusion (PBF) techniques such as Selective Laser Melting (SLM) also promotes material efficiency where unfused granular particles are recyclable after each forming operation in contrast to conventional subtractive methods. However, powder characteristics tend to deviate from their pre-process state following different stages of the process which could affect feedstock behaviour and final part quality. In particular, primary feedstock characteristics including granulometry and morphology must be tightly controlled due to their influence on powder flow and packing behaviour as well as other corresponding attributes which altogether affect material deposition and subsequent laser consolidation. Despite ongoing research efforts which focused strongly on driving process refinement steps to optimise the SLM process, it is also critical to understand the level of material sensitivity towards part forming due to granulometry changes and tackle various reliability as well as quality issues related to powder variation in order to further expand the industrial adoption of the metal additive technique. In this review, the current progress of Metal AM feedstock and various powder characteristics related to the Selective Laser Melting process will be addressed, with a focus on the influence of powder granulometry on feedstock and final part properties.

Existing Metal Additive Manufacturing processes are fast approaching a matured stage in which a wide range of possibilities are available for the incorporation of the rapid fabrication technology to current industrial practices. In terms of design conventions, the limitless geometrical freedom allows complex structures including cellular internal grids and lattices to be formed without additional tooling. Repair parts and leveraging components can also be produced on demand when required especially for military assets where large volume of inventory is constantly maintained to ensure operational readiness. In this exemplary work, a feasibility study on using stainless steel material with integrated cellular design to manufacture a guide bracket found on a military vehicle via Selective Laser Melting process was conducted. The results showed appreciably better mechanical performance in using a stainless steel honeycomb as compared to the aluminum alloy used for the original component together with a faster production route through SLM.