Characterization and Comparison of Friction Surfacing to Wire Arc Additive Manufacturing and Laser Powder Directed Energy Deposition

Abstract

The development of hybrid additive - subtractive manufacturing has created new possibilities for producing complex metal components with greater design flexibility, enhanced mechanical properties, and reduced post-processing effort. Fusion-based processes, particularly Wire Arc Additive Manufacturing (WAAM) and Laser Powder Directed Energy Deposition (LP-DED), have gained widespread use in structural applications. However, these techniques often suffer from drawbacks such as excessive heat input, large heat-affected zones, porosity, and anisotropy. Solid-state processes like Friction Surfacing (FS) present a promising alternative by eliminating the melting phase entirely. Instead, FS uses frictional heating and intense plastic deformation to deposit material, resulting in fine - grained microstructures and minimal distortion. This thesis examines the feasibility of FS as a solid-state additive manufacturing process through a direct comparison with WAAM and LP-DED. A standardized test artifact was fabricated using 316L stainless steel across all three processes. The evaluation criteria included deposition efficiency, hybrid efficiency, energy consumption, thermal distortion, microstructure, hardness, and mechanical strength. FS was implemented on a conventional 3-axis CNC milling machine, while WAAM and LP-DED were performed using a 6-axis robotic welding setup and a commercial hybrid machine tool, respectively. Among the three, WAAM achieved the highest deposition efficiency and the shortest cycle time. FS, by contrast, produced the least substrate distortion and the finest grain structure, owing to the absence of melting. LP-DED delivered the highest near-net shape accuracy, but also incurred the highest idle energy consumption due to its more complex machine architecture. The FS portion of the study offers valuable insights, particularly regarding the challenges associated with multilayer deposition. The lack of a shielding gas during deposition led to the formation of oxide layers between passes, weakening interlayer bonding and, in some cases, resulting in delamination. These issues adversely affected the tensile strength and consistency of the deposited material. Nonetheless, FS showed higher hardness near the substrate due to strain hardening. Interestingly, despite being a solid-state process, FS consumed nearly three times more energy than WAAM. This was primarily due to its slower deposition rate and the additional intermediate machining required between layers. While FS demonstrates several advantages as an additive process, this study also identifies clear areas for further development. The use of shielding gas could significantly reduce oxide formation and enhance interlayer adhesion. Additionally, fine-tuning parameters such as plunge depth, tool tilt, axial force, and substrate preheating may improve deposition uniformity and bonding strength. With continued refinement, FS has the potential to evolve from a niche coating and repair process into a viable solid-state additive manufacturing solution for structural hybrid applications.