Application Of Ti(C, N) In Carbon-containing Refractories

Titanium carbonitride is an excellent non-oxide ceramics with high melting point, high hardness, good wear and corrosion resistance, thermal conductivity, electrical conductivity and chemical stability. Nowadays, titanium carbonitride is widely used in machinery, chemistry, automobile manufacturing and aerospace industries. However, the use of Ti(C, N) in refractory industry is limited due to its high costs. A kind of inexpensive Ti(C, N)-containing composites was synthesized successfully by carbonthermic or aluminothermic reduction in the lab scale by Professor Li. Therefore, it is considered that Ti(C, N) composites can be applied in refractories in order to improve their properties.In this paper, the reactions between MgO and Ti(C, N), TiN, TiC, and effects of Ti(C, N) on properties (eg. bulk density (BD), apparent porosity (AP), cold crushing strength (CCS), modulus of rupture (MOR), high modulus of rupture (HMOR), linear change rate, oxidation resistance and slag corrosion resistance etc. ) of MgO-C, MgO-MA-C and Al₂O₃-C refractories were investigated by means of XRD, SEM, EDS and EPMA etc. The research work is summarized as follows:Firstly, the thermodynamic software Factsage was used to calculate the thermodynamics of reactions. The results showed that TiC and TiN could react with MgO to form gaseous Mg at 1600℃in vacuum atmosphere and in coke powder bed. The reaction between TiC and MgO occurred more easily than that of TiN and MgO. TiN and TiC could be oxidized in high O2 partial pressure more than 10-9 Pa. When the pressure of O2 was very low, TiC, TiN and MgO could coexist.Secondly, the reactions between MgO and TiN, TiC, Ti(C, N) were investigated. The results indicated that TiN, TiC, Ti(C, N) and MgO could form a solid solution to some extent at high temperature respectively. At 1800℃for 2h in vacuum atmosphere, the reaction between MgO and TiN carried out from the exterior to the interior gradually due to the kinetics factor, and all the outer MgO reacted with TiN, but the inner MgO did not react. However, MgO reacted with TiC completely to form TiO. At 1600℃for 3h in coke powder bed, TiN did not react with MgO, and yet TiC, Ti(C, N) could react with MgO to form Mg₂TiO₄.Thirdly, the effects of Ti(C, N) on performances of MgO-C, MgO-MA-C and Al₂O₃-C refractories were investigated. The results showed that Ti(C, N) could improve the oxidation resistance, slag corrosion resistance in air and the HMOR in coke powder bed of carbon-containing refractories. The effects of Ti(C, N) on the other physical properties and slag corrosion resistance in coke powder bed of refratories were not distinct. The optimum addition content of Ti(C, N) was 3wt% in MgO-C refractories and 2wt% in Al₂O₃-C refratories respectively.