M. Walluk, A. Luccitti, B. Hilton, B. Baker, K. Schipull
Rochester Institute of Technology,
Keywords: additive manufacturing, framework, additive friction stir deposition
Summary:Maintenance and sustainment of high value assets, such as vehicles, often relies on replacing damaged components rather than repairing them. In the case of components that no longer have a replacement option, additive manufacturing (AM) technologies are being considered to build these components from scratch through use of 3D printers. For some components this may be feasible, however, replacement using current 3D printing technologies is not always possible due to limited material options and inferior performance. Furthermore, replacement with new or printed components is usually more costly than repairing the existing assets. Due to these challenges the option to repair damaged components using maturing AM repair technologies is enticing to many industry practitioners, including those within the Department of Defense. Within the engineering community there is a knowledge gap in how to evaluate potential AM repair approaches against the original equipment part performance requirements, especially when original design information is unavailable. Additionally, each damaged component must be evaluated to understand the particular condition that resulted in removal from service. The performance and durability of repaired components must meet the requirements of the application, which is highly dependent on the AM technology and material combination used for the repair. Adoption of AM repair processes is currently limited by complexities associated with material properties and the need for a comprehensive, systemic solution for repair. One solution to this problem is the definition of AM repairs based on their operational and technological capabilities. The present work focuses on creation of a framework to determine if components are good candidates for additive repair and, if so, recommend an AM process and material combination which is best suited for the functions of the part. This task requires an understanding of both the initial performance of the part and the functional failures which cause the need for repair. The decision tool which recommends an appropriate additive technology must draw on a database of mechanical properties from a variety of process-material combinations. This presentation highlights one of the AM technologies being investigated, additive friction stir deposition (AFS), which adds material to a substrate through a thermo-mechanical process. Specifically, AFS for the deposition of aluminum 6061 (Al6061) onto similar Al6061 plate and cast aluminum tooling plate for repair is studied. A variety of defects with differing geometries are machined into the aluminum substrate materials to see how well the AFS process fills and bonds these defects. Material testing is conducted to gain better understanding of the as-deposited material properties compared to the original substrate properties. Analysis includes microstructure examination, static and fatigue strength testing, and wear resistance evaluation.