Rolling Assisted Wire + Arc Additive Manufacture of Meter-Scale Aerospace Components

Wire + arc additive manufacture (WAAM) uses arc welding processes for the purpose of additive layer manufacturing, i.e. 3D printing. WAAM is finding increasing industrial interest for the fabrication of meter-scale aerospace components. This is primarily due to the significant cost savings and reduced lead times offered by the process. For example, when using WAAM to fabricate aerospace components, buy-to-fly (BTF) ratios of 1.5 are typically achieved, values which are considerably less than those produced via subtractive manufacturing techniques.

The titanium alloy Ti-6Al-4V has received considerable attention with respect to WAAM. This is primarily due to its high cost and usage in the aerospace industry. In the as-deposited state Ti-6Al-4V WAAM components have large, columnar grains which produce anisotropic mechanical properties. The anisotropic properties are often undesirable for production components and are therefore hindering commercialization of Ti-6Al-4V WAAM. Recent research at Cranfield University has overcome this problem via the cold rolling of each deposited layer. The thermal energy provided by the subsequent layer combines with the stored energy of the cold worked grains causing recrystallization. The recrystallization produces a refined, equiaxed microstructure, giving isotropic mechanical properties that are superior to the Ti-6Al-4V parent material. To date, rolling assisted Ti-6Al-4V WAAM has only been investigated for small, linearly-deposited walls. There is a need to develop a multi-directional rolling assisted WAAM machine for the purpose of fabricating meter-scale Ti-6Al-4V aerospace components. Cranfield University is currently addressing this need.

In summary, this presentation reports on the benefits of the WAAM and interpass rolling processes and details Cranfield University’s development of a multi-directional rolling assisted WAAM machine.