Part Fabrication Using Multi-Material Additive Manufacturing

In recent years, the nuclear power industry has been exploring the use of conventional powder metallurgy and hot-isostatic press technologies to fabricate large, near net shape components for high pressure components and other applications pertaining to the generation of electric power. Powder metallurgy has many manufacturing consistency and reliability advantages over other large-scale manufacturing methods (e.g. casting, welding, forging etc.), which include the fabrication of near-net shape parts with controlled chemistry and improved microstructure in the part. Despite the advantages, there are drawbacks to today’s powder metallurgy/hot isostatic press processes. Large-scale parts are manufactured using these technlogies by first fabricating a conformal can, or mold, in a size slightly larger than shape of the part. The can is then uniformly filled with metal powder and evacuated, sealed, and placed in the hot isostatic press for processing. In general, the design and fabrication of the mold is critical to the successful fabrication of the part using this manufacturing process. Mold fabrication is both an engineering and labor-intensive process that involves the design and fabrication of a conformal mold that collapses under high pressure and temperature. In addition, the geometry of the parts fabricated in this process is limited by the mold geometry and the ability to uniformly fill the mold with metal powder, which is critical to the quality of the part. In the Phase I project, a novel multi-material 3-dimensional additive manufacturing was combined with powder metallurgy/hot isostatic press technologies; enabling the fabrication of parts not possible with conventional techniques. Metal parts were fabricated by multi-material printing metal and supporting powders in inexpensive steel molds and processing the molds using conventional methods. In addition, metal parts were fabricated by printing the metal, supporting, and mold powders in the same build cartridge. Subsequent processing of this multi-material powder structure resulted in the in-situ fabrication of the printed mold, which is then used to consolidate the metal powder in a hot isostatic press. These manufacturing processes not only allow for the fabrication of geometrically complex parts, they have the potential to significantly reduce tooling costs associated with the engineering and fabrication of conformal steel molds. The materials and manufacturing technologies demonstrated in Phase I will be matured in the Phase II project along with the development of additive manufacturing quality control processes specific to particular applications in the nuclear energy industry. In addition, working with industry partners, a prototype autonomous, multi-material, additive manufacturing microfactory will be designed, fabricated, and performance tested with the goal of providing high-value parts in low-volume per customer requirements. Commercial applications of this new additive manufacturing process include the fabrication of large-scale customized parts for commercial and federal customers, and the development of a completely new additive manufacturing microfactory system that will allow for the low-volume manufacturing of reproducible, high quality, geometrically complex near-net shaped parts at a reduced cost as compared to conventional manufacturing methods.