Prakt. Met. Sonderband 52 (2018) 335 
feat | 
li 0 (111) peak intensities of the reaction phase and TiC, respectively. It needs to be pointed out 
on Ho that this approach does not take into account the different atomic scattering factors of TiC 
Work and reaction phase and is, thus, only able to describe changes in reaction phase content, 
but not their quantitative amount. 
J von= lame 4909 (Eq. 2) 
WXRD Io wethrie a 
any) 
(my! 3. RESULTS AND DISCUSSION 
on 
ito a 3.1 General Microstructure and Reaction Phase Composition 
105 Wt 90) ans 
iL tang Fig. 1a shows an overview of the microstructure of the composite developed after HIP 
consolidation and heat treatment by means of a SEM image in electron-backscattered mode 
(SEM/BSE). While the dark grey contrast represents the TiC particles, the brighter grey 
wo contrast depicts the martensitic matrix phase. Due to the different average sizes of the TiC 
Ti and the steel powders, the TiC particles form a neckless structure around the larger steel 
—=2_1 particles. Although the material was not forged or rolled, only a negligible amount of pores 
mle remained. Higher resolution images, exemplarily shown in Fig. 1b, reveal an additional 
00°C u Der. phase besides TiC and matrix. It can be found at the surface of TiC particles and has a 
or 3 brighter BSE contrast suggesting an enrichment in elements that exhibit a higher atomic 
Sat ated number, such as Mo and W. 
nd three times 
00, 1200, 2400 ; ' 
2 spectroscopy 
X Apollo XLTW 
(field {HAADF) 
ja 40 scanning 
was also used 
ne Fig. 1: Micrographs of the M7 + 10 vol.% TiC after 6 h HIP consolidation. SEM/BSE 
images of the general microstructure (a) and higher magnification revealing a reaction 
" by manual phase at the TiC-matrix interface exemplarily indicated by red arrows (b). STEM/HAADF 
re image of an interface region showing matrix. reaction phase and TiC (c). 
wand Arca® To investigate the reaction phase composition in detail, a STEM/EDS study was conducted. 
hel The STEM micrograph is depicted in Fig. 1c, whereas the according EDS results are 
presented in Table 2. It can be stated that the TiC phase only contains Ti and C in 
measurable quantities. However, the reaction phase is considerably enriched in other 
carbide forming elements, but especially in vanadium. Thus, the reaction phase is denoted 
as (Ti,M)C wherein M means V, Mo, W, Cr, Fe in this work. The incorporation of these 
soniometer and carbide forming elements has been in excellent agreement with thermodynamic predictions 
conducted by for this system [6]. Moreover, the incorporation of W and Mo in TiC has been found 
3 T(Clreaction experimentally in steel based MMCs produced via liquid phase infiltration [3] and in W and 
tent from XRD Mo based MMCs consolidated by HIP [9, 7]. Mixed carbides from V and Ti on the other hand 
, tha intearated have been found in a super-solidus sintered steel based MMC [10]. In these works. the