| As cutting materials and wear-resistant materials, iron matrix composites reinforced by Ti(C,N) and/or Al2O3 have very high performances. The super-high cost of these composites, however, limits apparently their wider application to industry due to use of very expensive powder metallurgical process. Therefore, it is very necessary to develop a new process technology with low fabrication cost. In the present work, ilmenite (FeTiO3), which is very cheap and very rich in China, was used to fabricate the Fe/Ti(C,N) composite. Because of particularly low cost, this type of new technology for the Fe/Ti(C,N) composite directly from ilmenite will be very potential.The effects of process variables were systematically investigated on the carbothermic reduction process of ilmenite by differential thermal analysis, X-ray diffraction, optical microscopy, scanning electron microscopy, transmission electron microscopy and thermodynamic calculation. The basic reaction types of carbothermic reduction of ilmenite in different temperature stages were studied. More attentions were paid to effects of reaction temperature, carbon addition, iron addition, ball milling and reaction atmosphere on the reduction extent, reactive products, reactive speed, size and composition of Ti(C,N) compounds. The mechanism of these effects was discussed, the optimization process parameters and control methods of reduction reactions were suggested.Some very important results have been obtained. (1) There are two obvious endothermic peaks during carbothermic reduction of ilmenite at higher temperature range. The former is mainly due to formation of a Ti3O5 oxide, and latter mainly due to formation of a Ti(C,N) compound. The experimental results on the reactive products occurring during carbothermic reduction process of ilmenite were found to be consistent with the calculated ones. That is, TiO2 occurred at lower temperature stage, Ti3O5 at middle temperature stage and Ti(C,N) at higher temperature stage. (2) The mixed air was found to be favorable to carbothermic reduction of ilmenite and formation of Ti(C,N) compounds. The ideal reactive products for the iron matrix composites, iron and Ti(C,N), could be obtained at 1350-1400°C for 2 hours in the mixed air, but at 1600°C for 4 hours in nitrogen atmosphere without iron addition. (3) The endothermic peaks for occurrence of Ti3O5 and Ti(C,N), separately, during carbothermic reduction of ilmenite were decreased obviously by iron addition. The endothermic peak of Ti3O5 was lowered by 162°C with the addition of 1 mol iron in the FeTiO3-4C-xFe systems milled for 1 hour. With the same addition of iron, one of Ti(C,N) was decreased by about 80°C. (4) The carbothermic reduction speed of ilmenite could be increased apparently by iron addition. In the FeTiO3-4C system without iron addition, Ti3O5 oxide still existed after ilmenite was reduced even at as high as 1600°C in nitrogen atmosphere. With the addition of 1mol iron, however, Ti3O5 oxide disappeared completely at same reduction conditions. (5) Change of carbon addition from 2mol to 4mol was found to have little effect on the peak temperature of Ti3O5 and Ti(C,N). The peak temperature of Ti3O5 was about 1156°C, and one of Ti(C,N) was about 1360°C. The addition of 2mol carbon was found to be insufficient to realize complete reduction of ilmenite in the FeTiO3-2C-2Fe systems, and a lot of residual Ti3O5 oxide could be found in the composite. (6) The size of mixed powders of ilmenite, carbon and iron, was decreased obviously by ball milling. It was found that the average size of mixed powders could be lowered down to 36μm from original size of about 90μm by ball milling for 3 hour. (7) The endothermic peak temperatures of Ti3O5 and Ti(C,N) were decreased very apparently by ball milling in the FeTiO3-xC-xFe systems. It was found that the endothermic peak temperature of Ti3O5 could be decreased by 186°C by ball milling for 2 hours. The more milling time was found to have little effect on the peak temperature of Ti3O5. The ball milling from 1 hour t...
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