Those are alloys of chemical composition Fe + Cr + Fe with some additional elements and rare earth so as Yttrium, zirconium, Titan, Cerium, and Lanthanum which confer them:

  • An excellent resistance to oxidation under heat
  • A limitation of intergranular oxidation
  • A good life time


Alloys in question are:

Resistohm 125 – 135 – 140 – 145 – Y

Their metallurgical structure confers them nevertheless a cold plasticity lower than austenitic alloys (NiCr).

Advantages of FeCrAl compared with NiCr:

  • A higher resistivity (until 1.44 ohm mm²/m)
  • A temperature of use higher in the air (1300°C against 1200 °C for Resistohm 80)
  • A higher charge rate
  • A good resistance to sulphurous and carbonaceous atmospheres
  • A lower density which means: with an equal weight of material a more important number of elements (a cheaper unit price)


However:

  • A less important plasticity and a more difficult shaping
  • Mechanical behaviour limited and embrittlement after first heat
  • Possibility of corrosion more important because of the iron
  • Phenomenon of “path” more important (striction and elongation of the resistances)


Constraints:

 

  • Pre-oxidation often necessary
  • Minimal content in alumina of the supports: 60 % without iron oxide
  • In furnaces under atmosphere, initial coat of protective oxide to regenerate periodically.