The structure and properties of ferrite - cementite composites based on the mechanical synthesizing powder alloys of Fe-Cr-C system

The compact nanostructured composites from mechanical synthesizing powder alloys ((Fe$_{1-x}$Cr$_x$)$_{75}$C$_{25}$, (Fe$_{1-x}$Cr$_x$)$_{83}$C$_{17}$ and (Fe$_{1-x}$Cr$_x$)$_{95.5}$C$_{4.5}$, where х = 0; 0.05; 0.1) were obtained using magnetic pulse compression (MPC). After that, their structure contained cementite and ferrite. The density of compacts was differed from 81 to 97 % of the theoretical density and was depended from composition of alloys. The sequence of phase and structural transformations was studied on the all steps of processing (mechanosynthesis, consolidation, sintering). It was shown that the powder alloys on the unfinished stage of mechanical alloying may be used to produce of the compacts. Further annealing leads to the interaction of unreacted during mechanosynthesis phases and to the formation of the cementite. The influence of the duration of mechanical alloying, doping and annealing on the density, microhardness and wear resistance of the composites was studied. The highest value of microhardness for compacts with a carbon content of 4.5 and 17 at. % is observed after pressing and for compacts with a carbon content of 25 at. % it's observed after additional sintering at 700 $^{\circ}$C. The wear resistance of the compacts increases substantially after sintering and grows up with the increasing of the sintering temperature from 700 to 800 $^{\circ}$C. The greatest wear resistance under conditions of abrasive wearing shows samples which contain 25 at. % of carbon.