Relevant experimental phase equilibria were used with the THERMOCALC progra
m to refine thermodynamic parameters for the low-temperature region, in the
steels with composition 0.4 to 2.5 wt.% Cr, 0 to 1 wt.% Mo, and 0 to 0.5 w
t.% V. The refined parameters were used to calculate phase relationships, w
hich were then compared with experimental results.
The main interest was focused on the temperature and concentration regions
of existence of the chromium-rich carbides M7C3 and M23C6 and Mo-rich carbi
des M6C and MIG. Results of experiments indicate that M7C3 carbide replaces
M23C6 carbide in the temperature region between 773 and 873 K. Similar beh
avior was also found for molybdenum-rich phases M6C and M2C. Some modificat
ions of existing thermodynamic parameters in the low-temperature region, as
well as the establishment of some new parameters, were necessary to obtain
reasonable agreement between theoretical and experimental results.