Superalloy

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In high-performance aircraft, superalloys are traditionally used - here a MiG-25 .
Turbine blade of a gas turbine made from a nickel-based superalloy

As superalloys metallic materials of complex composition ( iron , nickel , platinum , chromium or cobalt basis with additions of the elements Co, Ni, Fe, Cr, Mo, W, Re, Ru, Ta, Nb, Al, Ti, Mn, Zr , C and B) for high temperature applications. They are mostly tinder - and highly heat resistant. They can be produced using either melt metallurgy or powder metallurgy .

The name superalloy indicates materials whose operating temperatures are higher than those of steels, as they have increased strength in this temperature range. Polycrystalline superalloys reach operating temperatures of around 80%, monocrystalline alloys around 90% of the melting point (homologous temperature). Nowadays, nickel-based superalloys are mainly used. Their temperature resistance is achieved through a mixture of incoherent dispersion hardening , coherent precipitation hardening and solid solution hardening .

Common brand names are e.g. B. Stellite , Tribaloy, Hastelloy , Incoloy , Inconel , NIMONIC , R88DT, Waspaloy or X-40 .

application

Because of their high price, but at the same time high permissible operating temperatures, superalloys are mainly used in engine, turbine and engine construction , in energy technology and in aerospace.

The materials of the components of gas turbines are polycrystalline (disks), directionally solidified or monocrystalline (blades). The aim of alloy development is to increase efficiency through the highest possible turbine inlet temperatures (currently a maximum of 1600 ° C with cooling). In order to keep the density and thus the weight of the components low, heavy elements are largely dispensed with in the alloys (example: tungsten and molybdenum).

Example: Inconel alloy 718

  • Material number: 2.4668
  • Short name: NiCr19NbMo
  • Density: 8.19 g / cm³
  • maximum operating temperature: 620 ° C.
  • Chemical composition: 0.04% C - 19% Cr - 3.0% Mo - 52.5% Ni - 0.9% Al - ≤0.1% Cu - 5.1% Nb - 0.9% Ti - 19% Fe.

This superalloy, reinforced with intermetallic precipitates (γ ″ phases), still makes up 60–70% of the volume of all nickel-based alloys today.

See also

Web links

literature

  • Ralf Bürgel: Handbook of high temperature materials technology: Fundamentals, material stresses, high temperature alloys and coatings. Vieweg, Wiesbaden 2006, ISBN 978-3-528-23107-1
  • Madeleine Durand-Charre: The Microstructure of Superalloys. OPA, Amsterdam 1997, ISBN 90-5699-097-7
  • DG Morris: Intermetallics and superalloys. Wiley-VCH, Weinheim 2000, ISBN 3-527-30192-5
  • John K. Tien: Superalloys, supercomposites, and superceramics. Acad. Press, New York 1989, ISBN 0-12-690845-1
  • Reed, Roger C. The Superalloys: Fundamentals and Applications. Cambridge, UK: Cambridge UP, 2006, ISBN 978-0-521-07011-9

Individual evidence

  1. ↑ Jacqueline Wahl, Ken Harris: New single crystal superalloys - overview and update . In: MATEC Web of Conferences . tape 14 , 2014, ISSN  2261-236X , p. 17002 , doi : 10.1051 / matecconf / 20141417002 ( matec-conferences.org [accessed July 26, 2020]).