Efficient repair of aircraft components is critical to the mission of the Department of Defense (DoD). Tradition powder based methods require expensive equipment that requires a large amount of energy to operate. They use expensive powders and the deposition efficiency may be as low at 15%. The powder that does not deposit has to be collected and treated as an environmental hazard. In addition, the powder manufacturing process if very inefficient with useful material utilization as low at 30% of the starting feedstock. Wire Arc Additive Manufacturing (WAAM) uses wire that is much less expensive than powder. The wire manufacturing process has a much higher material utilization that the powder production process. The use of WAAM offers significant energy and cost savings compared to powder based processes. The repair of worn components also offers large energy and cost savings compared to the fabrication of new components. The main technical objective of this project is to develop a fundamental understanding of the effects of processing on the material properties of materials deposited by the WAAM process through accurate modeling of the solidification and thermal process and through production and characterization of WAAM materials.

Feasibility Study

• Develop a heat transfer model to predict spatial and temporal temperatures and cooling/heating rates.
• Develop a solidification model that uses the results of the heat transfer model to predict cooling rates and starting temperatures to determine the microstructure and the formation and evolution of porosity.
• Produce small scale samples for a range of heat input and power cycle times that will be characterized for microstructure and porosity for calibration of the solidification and heat transfer models.
• Use the solidification models to predict the microstructure in large samples.
• Produce test article for microstructural characterization and materials property testing. Tensile testing will follow ASMT E8. Heat treating of the WAAM material will depend on the type of alloy selected.
• Compare model results with the experimental results and update the models to predict process-property relationships.
• Repair a component or test article with representative geometry using WAAM and the most promising process parameters as identified by the modeling and experimental results.
• Section the repaired article and test the mechanical properties. Compare the results of the repair with the results of the model.
• Update process-property relationships using the models.

This work will advance the state-of-the-art for WAAM alloys by providing a better understanding of the microstructural evolution of aluminum alloys used in aircraft components. Significant energy, material, time and cost savings can be realized by implementing the WAAM process. The total cost savings of this approach is estimated to be at least $15 million dollars per year based upon the manufacturing data from the DoD. This approach will form the foundation for additional development need to repair of a wide range of components. This program will result in a fundamental understanding of the microstructural evolution resulting from the WAAM process specific to repair of aircraft components determined by a physics-based modeling substantiated by experimental data.