Ti alloys with tailored oxygen content produced by plasma arc process (OXYgen CONtrol)

In recent years, the proportion of titanium alloys for aerospace applications has increased. A modern aircraft requires about 120-140 tons of titanium alloys in the form of plates, semi- finished products or raw materials, from which components are subsequently produced by means of forging processes or machining processes at about 20-25 tons. The ratio of raw material requirement to finished part is on average at a ratio of 6:1. This means in many cases more than 80% of the material is wasted.

For this reason, the aviation industry's trend is clearly moving towards the use of additive manufacturing technologies. Laser or electron beam based processes for the standard alloy Ti6Al4V are established and for components up to 500 mm in development or introduction. Nevertheless, such components are costly, because specific powders with high demands and thus high costs have to be used.

Powder bed processes are not suitable for the production of large components (> 500 mm) and, in addition, the production of large components requires the use of high deposition rate processes. For components with several kilograms the powder bed processes would be far too slow regarding the building time.

Additive manufacturing processes for components with a high buy-to-fly ratio and dimensions of &gt; 500 mm have not yet been widely used on the market.<br>The aim of the project is to produce plasma-metal deposition (PMD) process for the deposition of Ti6Al4V components using a wire-fed process that meets aerospace requirements and allows producing components larger than 500 mm.<br>A key challenge in the production of titanium materials is the sensitivity of titanium to oxygen. The content of oxygen in the built-up component has a serious influence on the properties. This affects not only the microstructure but also the mechanical properties (tensile strength, elongation at break, hardness, etc.) and even the machinability of the material.

The challenge that will be solved in the project is the development of an appropriate inert gas cell, which allows to monitor the oxygen content during the building process and to ensure by a inert gas control system that the oxygen content does not exceed certain limits.<br>In addition to the development of the gas control cell the influence of the starting materials (wires) will be also investigated and the process for high performance Ti6Al4V alloy will be developed.

In order to solve this task, several technological components are required which are jointly solved by the two companies SBI and RHP. The investigation of the raw material selection as well as characterization of these will be done by RHP. SBI will develop an inert gas cell including the monitoring system for the oxygen content. This will be implemented and tested at a PMD system at RHP in order to alloy subsequently control and / or ensure the properties in the Ti6Al4V by monitoring the oxygen and nitrogen concentration.

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