Decarburization of nanocrystalline TiC during sintering and its implications for in-situ reduction of Fe2O3 and fabrication of cermets

The present study shows that TiCxOy ceramics and TiCxOy-Fe cermets could be fabricated from nanocrystalline powders of TiC and TiC-Fe2O3. The ball-milled TiC contains a high amount of oxygen impurities, which are accommodated by the oxycarbide phase. Upon heating, oxycarbide partially decomposes via evolution of CO and promotes the reduction of Fe2O3 to a mix of Fe3O4/Fe starting from 400 degrees C. In the 550-700 degrees C range, Fe3O4 is converted to plain iron by oxidation of TiC, which increases the oxygen content in TiCxOy and leads to segre-gation of Ti4O7. At higher temperatures, oxide and oxycarbide phases of titanium continue to release CO, while Fe-based alloys melt at about 1400-1450 degrees C and facilitate densification. Depending on the starting content of Fe2O3, sintered samples demonstrate 0-24 vol% of metallic binder, 0.8-1.4 mu m grains, hardness of 7-18 GPa and toughness of 4-8 MPa center dot m(1/2).

Automated summary

The study demonstrates that TiCxOy ceramics and TiCxOy-Fe cermets can be produced from nanostructured powders of TiC and TiC-Fe2O3. Ball-milled TiC contains a significant amount of oxygen impurities, which are accommodated by the oxycarbide phase. Upon heating, oxycarbide partially decomposes, releasing CO and promoting the reduction of Fe2O3 to a mixture of Fe3O4/Fe. Fe3O4 is converted to pure iron through the oxidation of TiC in the 550-700 degrees C range, leading to an increase in oxygen content in TiCxOy and the segregation of Ti4O7. At higher temperatures, titanium oxide and oxycarbide phases continue to release CO, while Fe-based alloys melt at about 1400-1450 degrees C and aid in densification. Sintered samples exhibit a metallic binder content ranging from 0-24 vol%, grain size of 0.8-1.4 μm, hardness of 7-18 GPa, and toughness of 4-8 MPa·m(1/2).