Frieß, Jessica M.Sc.
Head of Investment Casting
Chair for comprehensive Foundry Science and Foundry Institute

Tel.: +49 (0) 241 80 - 98152

Precision Casting

To enhance or develop new, more diverse precision casting processes, a wide range of pant technology is employed; including wax injection, sanding and embedding equipment, a manually operated de-bedding machine and an ALD, VIM IC 5 S type multi-purpose vacuum casting equipment which operates according to the Bridgman principle. The basic specifications for this equipment are 1.5kg to 50kg casting weight, casting and heater temperatures range from 1700°C, and the maximum shell mould dimensions are 600mm diameter and 750mm height. This new equipment provides improved capabilities for analysing individual process steps, process parameters and solidification profiles and therefore offers new opportunities for influencing the microstructure. A deeper understanding of the process and the extra flexibility of manufacturing permits the process’ industrial applicability to be verified. Furnished with this equipment, enables research into the latest precision (investment) casting processes to be carried out. The development of the process includes all process steps: production of wax models, development of moulding materials, manufacturing of ceramic shell moulds, alloy development and casting methods. For example, the process development involves working with the newest fibre reinforced materials as well as with modern superalloys and other high-performance materials. In addition to this, the process development can be accompanied by simulations at any time.

NiAl microstructural reinforcement using directional solidification

A very promising class of materials are the high melting-point NiAl alloys, where the unsolved problem of high brittleness at room temperature has, up to now, prevented the industrial use of these alloys. For this reason, different methodological approaches to improve the mechanical properties are currently being researched.

Investigations performed in the project “NiAl microstructural reinforcement by directional solidification” are to examine the extent to which in-situ fibres/lamellae of the eutectic alloys NiAl-9Mo and NiAl-28Cr-6 Mo (at.%), produced by directional solidification, can constitute an effective microstructural reinforcement by means of pull-out, crack-bridging and crack-renucleation mechanisms.

Ni based superalloys

The manufacturing process for single-crystal gas turbine blades having complex constructions involve time consuming and expensive process steps and high material costs. As a consequence of the complex manufacturing process, a high rejection rate of defective turbine blades quickly leads to a low added value. For this reason, new cost-saving processes, reject-minimising optimised processes and alloy developments for reducing the expensive alloying elements are the focus of the following projects:

  • Innovative process technology (DWDS) for directional solidification
  • Ability to undercool superalloys using the alloying elements Co, Re and Ru
  • Formation mechanism of the casting defect “freckles”
  • Minimising the rejection rate by reducing large-angled grain boundaries at changes in cross-sections during directional solidification

Centrifugal casting

Among others, a Linn and a Selecast centrifugal casting machine enables precision casting to be carried out. Die-casting is carried out using a MBS-Senator centrifugal casting machine. The latter can be operated at a freely adjustable tilt-angle using variable rotational speeds. The maximum casting weight is 5 kg Mg or 8 kg Al. The equipment is employed for developing alloys and processes, for determining process parameters as well as for manufacturing composite castings and fibre reinforced materials.