Study On Preparation And Passivation Of TiC_x By Mechanical Alloying

Mechanical alloying（MA）was a commonly used method for preparing non-stoichiometric compounds,which can uniformly prepare nano-sized powders.However,the prepared powder has high internal energy and surface energy,so the reclaiming process often needs to be carried out under a specific inert gas.In this topic Ti powder and TiC powder were used as raw materials to prepare TiC_0.4 by MA method.By changing the loading and reclaiming environment of material and the standing time before reclaiming,the influence of different processes on the MA process and products was explored,and the simplest process was sought.The passivation agent was introduced in the process to passivate the MA product,and the influence of the type of passivation agent,the time node of the addition of the passivation agent,and the air tightness of the mill jar on the MA product was explored.The influence of different loading and reclaiming environment of the material and standing time on the MA process and products was explored,it was found that the air can promote the refinement of MA and improve the reaction efficiency.Compared with loading in the glove box,loading in air can introduce more oxygen,and the degree of oxidation so low under the influence of oxygen partial pressure that only TiC_xO_y phase was formed.Regardless of the loading environment,the product taken out in the glove box will not ignite spontaneously,and the product will ignite spontaneously when taken out in the air.There was no obvious change in the phase of product under different loading and reclaiming environments.The product was taken out 0 hour,1 hour and 4 hours after the end of MA respectively.The different standing time had no obvious effect on the phase and oxygen content of the MA product.The influence of the type of passivation agent and the time node of passivation addition on the product was explored.The material was putting in the jar under the air.When the air introduced into the jar after milled 45 hours,the powder was not spontaneously combusted under the air after the MA,and the main phase of the product is still TiC_x,and a small amount of TiO_x phase was formed.SPS sintering was carried out under the conditions of 1600℃and holding time for 10 min.The main phase of the sintered body was still TiC_x with a small amount of TiO₂.The hardness was 13.8GPa and the fracture toughness was 4.8MPa·m^1/2.TiC_x was prepared by MA using a mill jar with poor airtightness.The material was putting in the jar under the air without any passivation gas.The product was taken out under the air without spontaneously combusting.The product had a TiO_x phase,but the sintered body was still better overall performance.The density of the sintered body was97.37%,and the hardness and fracture toughness of the sintered body were 14.3GPa and5.08MPa·m^1/2.The sample was subjected to thermal analysis,and its initial oxidation temperature was 362.9℃,which was nearly 50℃higher than TiC_x（314.6℃）prepared by the normal process.The passivated TiC_x was sintered with WC at 1600℃.Due to the reduced activity of the powder,the density of the sintered body was only 86.11%,and the hardness was only10GPa,which were far lower than the TiC_x-WC composite under the normal process.At1700℃,the density was significantly increased to 95.12%,and the hardness and fracture toughness were 21.3GPa and 8.5MPa·m^1/2 respectively,which were close to the one under the normal process.