Hitachi

Hitachi Metals America

ZMG®232L is a Fe-22%Cr ferritic alloy with a small addition of special elements for Solid oxide fuel cell (SOFC) interconnector which is alloy-designed and developed to obtain these required properties at the same time.

SOFC is a promising fuel cell with high efficiency operated at high temperature in the range of about 600 to 1000°C(1112 to 1832°F). Good properties are required for SOFC interconnector material as follows;

  1. Good electrical conductivity at operating temperature,
  2. Good oxidation resistance at operating temperature for a long time,
  3. Coefficient of thermal expansion close to electrolyte material YSZ (zirconia ceramics).

There are some problems for conventional heat-resistant alloys as follows;

  1. 430 Stainless Steel does not have sufficient oxidation resistance,
  2. Austenitic alloys with good oxidation resistance such as In 600 have much higher thermal expansion than YSZ,
  3. Al-containing ferritic alloys with better oxidation resistance than austenitic alloys have low electrical conductivity of oxide layer.

Chemical Compositions of ZMG®232L (mass %)



Oxidation Resistance & Electrical Contact Resistance Data at 1000°C(1832°F)



Oxidation Resistance and Electrical Contact Resistance in air


Notes:*1 ( ); Exfoliated scale (mg/cm2)
*2 Electrical contact resistance was measured at each oxidation temperature after oxidation.



Oxidation Resistance and Electrical Contact Resistance in air



Microstructure of oxide layer of ZMG232L compared with 430SS


Note : 430SS after exposure at 1000°C(1832°F) for 100hrs formed oxide scale of about 400μm thickness.



EPMA element map of oxide layer of ZMG232L at 750°C(1382°F) for 6000hrs in air



Physical Properties



Tensile Properties of ZMG232L at Room Temperature to 800°C(1472°F)