Preparation And Tribological Properties Of Ti₃SiC₂ Matrix Composites

Traditional friction brake materials use metal as matrix,and most of them add graphite as lubricating component.However,graphite has poor oxidation resistance at high temperature.When the working temperature of friction brake material rises to a higher level,graphite oxidation becomes serious and thus loses its lubrication characteristics.Ti₃SiC₂ has a layered structure similar to graphite and has good self-lubricating properties.Its thermal conductivity,thermal shock resistance and high temperature oxidation resistance are all better than graphite.Replacing graphite with Ti₃SiC₂ is undoubtedly a good option.However,metal materials as binders?usually Cu-based?also have poor oxidation resistance.If Ti₃SiC₂ wear resistance and poor strength are compensated by suitable materials and combined well with them,friction brake materials used at higher working temperature may be obtained.In this paper,Ti₃SiC₂ composite friction materials were prepared by SPS method with TiN_0.3,TiC_0.4 and chopped carbon fibers added to Ti₃SiC₂ respectively.The effects of type and content of reinforcing phase and sintering temperature on phase composition,mechanical properties and friction and wear properties of Ti₃SiC₂ composite were investigated.The experimental results show that:?1?TiN_0.3 and TiC_0.4 can obviously improve the strength of Ti₃SiC₂.The main reason why TiN_0.3 and TiC_0.4 enhance Ti₃SiC₂ is that covalent bond compounds are added as binders to increase its strength,and TiN_0.3 can also promote the decomposition of Ti₃SiC₂into TiC and Ti₅Si₃ hard phases to increase its hardness.?2?In the sintering process,Ti₃SiC₂ reacts with carbon fibers to form?-SiC on the surface of carbon fibers,and partially decomposes Ti₃SiC₂ into hard phases such as TiC,Ti₅Si₃ and a small amount of TiSi₂,which improves the strength of the material.?3?Considering the factors such as wear,friction coefficient and strength of the composites,the composites prepared by adding 20vol.%carbon fibers and sintering at1300?have the best tribological properties.The friction coefficient is 0.53,the wear rate is 0.008 mg/m and the hardness of the material is 7.4 GPa.Compared with pure Ti₃SiC₂,the wear rate decreases greatly and the strength increases.The thermal conductivity is55-73 W/?m.K?.TiO₂ film can be formed in the friction process,so it has excellent high temperature oxidation resistance.