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Towards Solid-State Recycling of Ti6Al4V: Defining a Sustainable Machining Process Window for Low-Oxidation Chips

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Abstract:

Titanium is a Critical Raw Material for the European aerospace sector, yet its manufacturing is characterized by high buy-to-fly ratios and significant waste in form of chips. Solid-state recycling (SSR) presents a low-energy alternative to remelting for chip revalorisation. However, its viability is strictly limited by their oxidation. This study investigates the influence of milling parameters (cutting speed and radial depth of cut), and coolants (emulsion, LCO2 and dry), on cutting forces and chip quality (morphology and oxidation) to define a process window for generating low oxidation chips, enabling further SSR routes. By correlating cutting forces with chip analysis, the results reveal that emulsion cooling yields the chips with the least oxidation, despite potential oil contamination of the feedstock with oils. While LCO2 effectively reduces oxidation at lower material removal rates, high thermal loads overwhelm its cooling capacity, resulting in oxidation comparable to dry cutting. These findings establish the machining parameters necessary to produce high-quality, recyclable feedstock, bridging the gap between subtractive manufacturing and circular material flows.

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Periodical:

Defect and Diffusion Forum (Volume 450)

Pages:

127-137

DOI:

https://doi.org/10.4028/p-TB3Cbv

Citation:

Cite this paper

Online since:

April 2026

Authors:

Gorka Ortiz de Zarate, Iñigo Rodriguez, Ainara Oruna, Harry Otalora, Mikel Etxebeste*, Pedro José Arrazola

Keywords:

Oil-Free Machining, Recycling, Sub-Zero Cooling, Titanium

Funder:

The publication of this article was funded by the Mondragon Goi Eskola Politeknikoa, J.M.A. S.Coop

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* - Corresponding Author

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