Prakt. Met. Sonderband 46 (2014) 161 
microscope In order to get more shrinkage during 
er sintering, gravity sintering was carried out. 
Therefore the tapped Fe21Cr powder was 
ji has been sintered at 1300°C for 60 min in Ha. 
J. First, the Although the porosity with 42% is higher 
matically by than with the pressed sample, the pores are 
‘In the next again well distributed (Fig. 6) and no larger 
as analyzed pores can be seen. The tap density (= 
ntage of all starting state or green density) was 
measured as 3.44 g/cm3, the sintered 
density was 4.40 g/cm? The shrinkage in 
200 pri direction of the gravity force was measured 
—_ Lc ——— sama as 13.5%, but the shrinkage is surprisingly 
Fig. 6: Fe21Cr, gravity sintered, 100x, 42% rather anisotropic. The shrinkage in other 
porosity directions was markedly lower (around 3%). 
Table 2: Comparison of calculated porosities with different magnifications 
| metallographic calculated 
; Sample manufacturing magnification porosity Fiji ' porosity 
| process % 0%)* 
; Fe21Cr | gravity sintered , 50x | 31,5 42 
. Fe21Cr pressed 50x 40,0 39 
So. Fe16Cr | MIM 50x 29,1 26,5 
Yi 200 um 4 Fe21Cr ' gravity sintered 100x 28,7 42 
wax, 100% “Fe2iCr 100x 38,0 3 
(dewaxed Fe16Cr MIM 100x 26,5 26,5 
sity *This porosity was calculated from the density by using the following formula: 
porosity [%] = (1 —(psintered / ptheoretical)) * 100 
In Table 2 a comparison of the porosity determined with the Fiji software and the 
=! calculated porosity with the formula quoted above is presented. It is already known that the 
separation of the section area surface into pores and matrix is influenced by the 
microscope magnification used and different magnifications can lead to different results for 
the porosity [8]. For the MIM and for the pressed samples the porosity values are quite the 
same. For the gravity sintered sample there is a big difference, and it is assumed that the 
impregnation of the gravity sintered samples didn’t work out properly. Normally, if the 
samples are soaked up with water, higher densities (= less porosity) are expected to be 
a measured. In any case, the sintered density of the gravity sintered samples has to be 
a analyzed further (f.ex. with DIN EN 1389, measuring the porosity with immersion liquid). 
PR 
Aa 
3 200m 4. CONCLUSION 
sintered 
n, 26.5% Usually a porous metal support for a SOFC is produced by tape casting or spray 
deposition. In the present work, alternative methods like uniaxial pressing and sintering, 
gravity sintering or metal injection moulding were tried. The samples were then 
characterized by density, shrinkage and with special regard to porosity as well as