Recycled Titanium Chips as Initial Product for the Atomisation Process of Powders for Additive Manufacturing to Increase Resource Efficiency

Abstract

The established process chain for the fabrication of titanium alloy components consists of the production of titanium sponge, the melting process, the forging process and the milling process. High energy demand in producing the initial titanium workmaterial of about 85% of the overall process energy consumption and high chip removal rates in milling up to 95% results in high carbon dioxide footprints and high part costs. Additionally, resulting chips do not meet the quality required for recycling in high-grade titanium alloys, because of the formation of process-induced contaminations. Thus, the major part of the chips from titanium alloys like Ti-6Al-4V is downcycled to ferrotitanium alloy. This paper introduces a novel process chain to recycle titanium chips directly for the use in fabrication of titanium powders for powder bed fusion additive manufacturing without any cost intensive remelting in aerospace grade quality, closing the loop in additive subtractive manufacturing. A methodology to increase the recycling rate of chips by investigating and adapting the influencing machining and process parameters on chip quality is shown in this paper. Cleaning and compaction processes open the possibility to use titanium chips as base material for atomisation processes. By reducing process-induced contaminations and using a recycling process for chips, the energy demand for the production of titanium powder can be significantly reduced by approximately 72% in comparison to standard powder production. Thus, the fabrication of recycled titanium powders brings new possibilities in extending additive manufacturing process scope and lower part costs significantly.

Keywords: Energy efficiency; sustainable manufacturing; recycling