Titanium carbon nitride, a new material of the century

In the manufacture of all kinds of mechanical parts, all need to be processed with cutting tools. The cutting performance of tool material is one of the key factors to determine the machining efficiency, machining quality and machining cost. WC-Co – based carbide tool is the most used tool material at present. However, tungsten and cobalt are rare resources, resulting in high cost of WC-Co based cemented carbide materials.

Carbon titanium nitride material with high melting point, high strength, wear resistance, corrosion resistance and oxidation resistance and other excellent characteristics,  that combines the advantages of TiC and TiN, in addition to very suitable for high precision machining and near net forming, it is based on TiC characteristics, due to the introduction of N, dramatically improve TiC brittle characteristics. With the increase of N content, the hardness decreases and the toughness increases. Because of its excellent comprehensive performance, titanium carbonitride ceramics have been widely used in the field of cutting, high temperature resistant materials, measuring tools, petroleum and chemical industry, clock appearance and other fields.

Titanium carbon nitride powder preparation
01 High temperature solution method
High temperature solid solution method is the traditional method of preparing Ti(C, N) powder, which is usually formed by a certain amount of TiN and TiC powder mixed evenly at 1700 ~ 1800℃ high temperature, or in Ar or N2 atmosphere at higher temperature through solid solution. In order to restrain grain growth and improve powder activity and sintering properties, the solution temperature can also be appropriately reduced. Even if the solution temperature is reduced, the high temperature solution method still has some shortcomings, such as too high reaction temperature, high energy consumption, difficult to obtain high-purity powder, and difficult to accurately control the N/C ratio.

Nitriding of 02TiN and C powder at high temperature
High temperature nitriding method is usually based on TiN powder and C powder as raw materials, mixed in high temperature and N2 or Ar atmosphere for a long time carbon nitriding treatment, so as to obtain Ti(C, N) powder. Frederic et al. used nano-sized TiN powder +10wt% carbon black to hold at 1430℃ in Ar airflow for 3h, and the solid phase was combined into Ti(C, N) powder, showing regular shape of submicron particles. Similarly, the high temperature nitriding method has the disadvantages of too high reaction temperature, low production efficiency, high energy consumption and high production cost.

03TiO2 carbothermal reduction nitriding process
Carbothermic reduction nitride process is a process of synthesizing Ti(C, N) powder by reducing TiO2 and C powder in N2 medium and high temperature. The size and morphology of the product of carbothermic reduction process can be controlled by process parameters, which is widely used in industrial large-scale production.

04 Sol-gel method
In sol-gel method, TiO(OH)2 sol is used as Ti source, carbon black is mixed and dispersed in liquid phase, and Ti(C, N) powder is obtained by heat treatment under N2 after a series of reactions. Some researchers obtained Ti(Cx, N1-x) by drying the gel formed by mixing TiO(OH)2 sol with nanoscale carbon black at 1400 ~ 1600℃ under N2 atmosphere, where 1-x=0.2 ~ 0.7, the average particle size of Ti(Cx, N1-x) ultrafine powder

05 ammonia solution
Ammolysis method is usually at room temperature, TiCl4 is dissolved in appropriate solvent and added additives, mixed evenly and react with NH3 to generate a homogeneous mixed intermediate of amine compound of Ti and additives, and then the intermediate is mixed with NH4Cl solution to precipitate and remove the amine in the intermediate. The Ti(C, N) powder was obtained by pyrolysis under vacuum or Ar atmosphere at 1200 ~ 1600℃. Ammonolysis method is characterized by lower preparation temperature than traditional preparation method (high temperature solution method, 1800℃). The Ti(C, N) powder obtained has the advantages of high specific surface area, small particle size, concentrated particle size distribution and high purity, but the cost is high and the process is complex.

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