Cost Reduction of TiAl by Alternative Production and Integration of TiAl Scrap Recycling — Concepts and Vacuum-Metallurgical Equipment

Abstract

Due to high corrosion resistance and low density titanium aluminides show a great potential as material for structural applications in the aerospace and automotive industry. However the high actual production costs for semi-finished products slow down a break through to mass production of TiAl. Current research projects at IME, Aachen funded by AIF "Otto von Guericke" and BMBF aim on cost reduced production methods of TiAl and on the minimisation of downgrading TiAl scrap. This article presents firstly the state of the art of TiAl production by vacuum arc (re)melting (VAR) or induction skull melting (ISM). A comparison of new process routes under special consideration of recycling issues will follow. Innovative processing and equipment concepts are shown by intelligent combination of well known vacuum melting and remelting processes such as vacuum induction melting, specialized using ceramic lining and deoxidisation with e.g. electro slag re-melting (ESR). For each process step and accordingly equipment the metallurgical opportunities are pointed out and the way to make use of them within the process route is described. Requirements on input material and final metal quality addicted to the processing route and refining techniques with their adjustment in respect to TiAl are mentioned. Selected results of laboratory and pilot scale experiments done at IME in Aachen and equipment needs therefore are shown.

A Closed‐Loop Recycling Technology for γ‐TiAl from Precision Cast Low Pressure Turbine Blades

“…In comparison to commercial pure titanium, Lochbichler [6] shows a remarkably decreased titanium activity in TiAl alloys (Tab. Furthermore, VIM offers the possibility of online sampling and composition corrections.…”

“…Furthermore, VIM offers the possibility of online sampling and composition corrections. In comparison to commercial pure titanium, Lochbichler [6] shows a remarkably decreased titanium activity in TiAl alloys (Tab. 1).…”

“…Based on this circumstance; IME Process Metallurgy and Metal Recycling (IME) developed a closed loop recycling process for titanium-aluminide scraps. Extensive research on the individual process steps has already been carried out and was published by Stoephasius [5], Lochbichler [6] and Reitz [7]. In cooperation with ACCESS Technology (ACCESS) it was now possible to evaluate the entire process from scrap material to finished precision cast low pressure turbine (LPT) blades.…”

“…Dissolved Ca and Y in CaO and Y 2 O 3 saturated liquid TiAl versus dissolved oxygen at three different temperatures. Note: a(CaO)a(Y 2 O 3 ) = 1[6,9,10].…”

Emission mitigation potential of lightweight intermetallic TiAl components

“…The Vacuum Induction Melting (VIM preliminary melting and deoxidation) þ Pressurised Electro-Slag Reduction (PESR deoxidation) Vacuum Arc Re-melting (VAR-compositional refinement) -is the preferred route, [15,16].…”