Study On Anticaustic Ability Of In-situ Synthetic TiC-TiB₂ Cermet In Hot Fluoride Salt

In this paper,the thermodynamic calculation and composition design of the in-situ synthesis of TiC-TiB2 cermet were carried out.The TiC-TiB2 cermet was prepared by hightemperature sintering and vacuum lost foam casting.Use scanning electron microscope,X-ray diffractometer,density measuring balance to observe the structure,density and porosity of TiCTiB2 cermet,and conduct corrosion resistance research in 1100°C high temperature Al F3-Na F fluoride salt.The main findings are as follows:Under standard conditions,the reaction of synthesizing TiC-TiB2 ceramic phase is ?H?<0,?G?<0.The enthalpy change of the TiC formation reaction is-184.1 k J/mol,and the enthalpy change of the TiC-TiB2 formation reaction is-502.7 k J/mol,which is an in-situ synthesis reaction.When gold,iron or aluminum is added during the reaction,increasing ?H inhibits the progress of the reaction.When the amount of iron added in the TiC formation reaction is higher than 1.85 mol and the amount of aluminum added is higher than 2.27 mol,or the reaction of B4 C and Tito form TiC and TiB2,the amount of iron added is higher than 5.2 mol,and the amount of aluminum added is higher than 6.6 mol,or the reaction of B4C?C and Tiproduces TiC and TiB2.The addition of iron is higher than 6.8mol,and the addition of aluminum is higher than 8.7mol,?H??0,and the in-situ synthesis reaction cannot occur.Through the composition design,the preform is prepared and put into the intermediate frequency furnace for high-temperature sintering of TiC and TiC-TiB2 cermet samples.The true density of TiC-TiB2 cermet is higher than that of TiC cermet,and the surface morphology is rough and there are a lot of holes;The true density of the cermet prepared by the lost foam casting method is significantly increased,the true porosity of TiC-TiB2 cermet is lower than11.24%,and the true porosity of TiC cermet is higher than 27%.In an air atmosphere,the AlF3-NaF high temperature resistance to fluoride salt corrosion test was carried out at a temperature of 1100°C and a holding time of 12 h.The weight loss rate of TiC cermet was up to 45.5%,and the weight loss rate of TiC-TiB2 cermet was up to 7.7 %,the corroded surface is uneven,and the main products are iron-aluminum oxide and fluoride.The corrosion resistance of TiC-TiB2 cermet samples is higher than that of TiC cermet.Through the analysis of the fluoride salt corrosion resistance of the cermet sample,the more TiB2 phases in the cermet,the stronger the fluoride salt corrosion resistance,the more aluminum is added,the weaker the corrosion resistance,and the corrosion resistance of iron is stronger than that of aluminum;The degree of corrosion of cermet materials is related to the true porosity of ceramics.The larger the true porosity,the lower the resistance to high-temperature fluoride salt corrosion.The true porosity of TiC-TiB2 cermet is lower than that of TiC cermet,and the resistance of TiC-TiB2 cermet is The corrosion characteristics of fluoride salt are higher than that of TiC cermet.