The Influence Of Oxygen On TiN_0.3 Or It And Refractory Metal Sintering

Non-stoichiometric ratio TiN_0.3.3 as an excellent binder for PCBN tool materials which could be sintered densification at lower temperature and it had the function of high hardness,high temperature resistance,abrasion resistance and good chemical stability,but because of the high concentration of N vacancy in the crystal,it’s property structure was unstable,At the same time,nano-scale powder was easy to absorb air and occur oxidation.In this paper,the oxidation of TiN_0.3.3 nano-powders was studied,and the results showed that the initial temperature of oxidation of TiN_0.3 was 315.6℃,and the initial oxidation product was TiN_x O_y,the oxidation product change into A-TiO₂ at 360℃and the product became the most stable R-TiO₂ at 532℃finally,.Second,when TiN_0.3 was at high temperature and high pressure sintering,the structure was oxidation,because the TiN_0.3 adsorped oxygen and reacted in the powder,the product was Ti₂O₃.In order to explore the influence of oxygen element on TiN_0.3 sintered body,different content of oxygen element was introduced to TiN_0.3 nano powder to explore the change of sintering body’performance at high temperature and high pressure.Under the conditions of 5 GPa、1000°C’s sintering temperature and 10 min’s hiolding time,the hardness of non-oxidized TiN_0.3 sintered body was 19.9 GPa and the toughness was 3.56 MPa·m^0.5.After oxygen was introduced into powder,the oxidation phase of the sintered body was R-TiO₂,With the increase of oxidation phase（17 wt.%-59 wt.%）,the bonding of particle in the sintered body became poor,the crystal formed poorly,and the hardness and toughness were drastically reduced.When the content of oxygen in the powder was small（about 5wt.%）,the TiN_0.3 powder was activitily and it’sintering temperature was lowers,because the oxygen atoms diffused into the TiN_0.3 crystal lattice and the powder particles had lattice defects,and the best mechanical properties that compared with the non-oxidized TiN0.3 sintered body were improved.This paper explored the effect of oxygen content on the composite sintering of70 vol.%TiN_0.3-30 vol.%Mo₂C、70 vol.%TiN_0.3-30 vol.%ZrC.The results showed that the existence of oxidized phase in the high temperature and high pressure sintered body inhibited solid solution of the 70 vol.%TiN_0.3-30 vol.%Mo₂C which led to the large MoC phase increasing and the sintered body structure loosening and the mechanical properties deteriorating which compared withnon-oxidized sintered body.In the70vol.%TiN_0.3-30vol.%ZrC composite sintered body,Zr atom reacted with oxygen that was in the powder and formed two crystal forms ZrO₂（monoclinic D-ZrO₂ and orthogonal structure Z-ZrO₂）,With the increase of oxygen content,the content of solid solution was reduced,the structure of sintered body was loose,and the small particle ZrO₂ increased,which caused the mechanical properties of the sintered body to decrease.