Description: The goal of this project is qualification of the friction stir additive process with the tradename of "MELD" for printing additively manufactured parts. It also includes using the process to weld dissimilar materials. The process uses a square feedrod that is fed down the center of a rotating tool, and the spinning tool plastically deforms the material, which is then deposited as a layer of the material that is approximately the width of the tool and 1 mm to 2 mm high. The process is solid-state (meaning no melting occurs in the constituent materials) so it can use alloys that are generally considered un-weldable / printable with fusion additive methods. It also has a much higher deposition rate than the other processes and the deposited metal has a uniform equiaxed microstructure. The process is planned to be used to make ring forging replacements along with other structures that have long lead times and are expensive to build. The need for the process also extends to in-space manufacturing as solid state depositions are able to have all of their critical parameters tested on Earth since they are not sensitive to gravitational variations like fusion melting / solidification additive and welding processes are. The process may also be useful for welding dissimilar alloys with a large gap between (one that would typically be to large for friction stir welding or fusion methods such as laser beam welding or electron beam welding. This would provide a valuable manufacturing method for both on Earth and in space applications.

Benefits: The friction stir additive manufacturing process has high deposition rates, and it can deposit alloys that are considered un-weldable with fusion-based systems. It is designed to build large-scale parts but is also suitable for smaller-scale items too. Although the printed parts must be machined after printing, the refined equiaxed microstructure coupled with the rapid build rate offset this added cost. Because the printed metal does not melt there is significantly less shrinkage than fusion based metal printing which leads to significantly less distortion and reduced residual stresses. The reduced distortion means less build plate adherence issues, as fusion-based additive processes can have issues with build plate separation. It also means there is less distortion modeling that needs to be done to ensure the proper geometry post build. The type of typical defects seen with the MELD process are unknown to NASA and Blue Origin, but if they are similar to friction stir welding defects they would be less likely to be crack like than with a fusion process. .