Prakt. Met. Sonderband 38 (2006) 275 
of boron. used to analyze the EFTEM images and/or TEM bright field micrographs. For each 
92) and specimen an area of about 40 um? was quantitatively analyzed. 
over the 
WVNDbN- For the conventional TEM measurements metal foils were prepared by mechanical cutting, 
je further grinding and chemical etching using a Tenupol-3 from Struers. Most of the analytical TEM 
cordingly. investigations were performed on formvar extraction replica. Detailed information about the 
event the two applied preparation techniques is given in [16]. Each precipitation type was 
ment by characterised by electron diffraction to determine the crystallographic structure and by 
by Fujita EDX measurements to determine the chemical composition. EDX was done on 
ut 300 to approximately 80% of all particles visible in the TEM micrographs. The electron diffraction 
of the hot experiments were performed on selected particles using either a parallel beam for selected 
riences it area diffraction or by convergent beam electron diffraction (CBED). A detailed description 
less, the of the applied methods can be found in [17]. 
analysis 
eels with 2.3 Material 
a for the 
w of the For the microstructural investigations material in the initial state and creep-ruptured 
samples tested at 650 °C were used. The creep test on the TAF steel specimen has been 
performed at 650 °C with a load of 100 MPa for 26 931 hours and the investigated 
ölklingen, specimen of FB8 has been tested at 650 °C for 19436 h with a load of 70 MPa. The 
ests have chemical composition of the test melts, the heat treatment data and the 0.2 limit at room 
e shown temperature after heat treatment of the samples TAF and FB8 are presented along with 
the creep data for these two alloys in Fig. 1. 
Test Temperature 650°C 
300 
200 
met. The - 
. grinding 
% HNO, 199 = 
OL JSM BY — DE % 
acquiring © 80 - — . oo si 
lispersive 4 Typ € Si Mn Cr Mo Co ~ V Nb . B Al Heat Treatment Rp0.2 
lection of 40 I A TAF 21 33 87 105 154 - <02 2418 O17 030.014 1n1150°C/OW+2h700°C  BTOMPa 
done at 1 {1 FB8 17 09 ‚09 11.1 1.46 2.94 20 .21.070 .023 .010 .005 4h1100°CIOI+10hETOCH10hT20°C 718MPa 
the TEM 30 Firm Ds a Si — 
100 1000 10 000 100 000 
Time to fracture in h 
Fig. 1: Creep resistance of the TAF and the FB8 steels tested at 650 °C. 
erformed 3. Results and Discussion 
size and 
an EDX The general microstructure of the specimen can be obtained by LOM. Fig. 2 shows as an 
in atomic example the as-received FB8 and TAF steels which exhibit a ferritic-martensitic structure. 
lemental Prior austenite grain boundaries and martensite laths are visible. The former austenite 
be found boundaries and also mainly the subgrain boundaries are decorated with precipitates. 
en a which can be observed by SEM and TEM (Fig. 3).