Study On Preparation And Tribological Property Of SiC Reinforced Ti-Al-C Ternary Layered Ceramics

Ternary layered(also known as MAX phase)ceramics have a variety of properties,including low hardness,low density,high modulus,great electrical and thermal conductivity,damage tolerance,excellent high temperature oxidation resistance and thermal shock resistance performance.It also has machinability comparable to graphite.However,its lower strength than other ceramics limits its application range.In this dissertation,SiC reinforced MAX composites were prepared.Trying to explore the influence of phase composition on the mechanical and tribological properties of composites.In this dissertation,a series of composites were prepared by mixing SiC powder with Ti3 Al C2 powder in different mass fractions(0,9 wt.%,15 wt.%,20 wt.%).The phase composition of the material was analyzed,and it was found that the addition of SiC would trigger a reaction during the hot-pressing sintering process,which caused the MAX phase change from Ti3 Al C2(0TAC)to Ti3 SiC2.9TAC,15 TAC and 20 TAC are composed of Ti C,SiC(excess ratio)and Ti3 SiC2.The relative densities of the composites are all greater than 96%.Density and relative density of the composite decreases significantly due to the remaining low-density SiC particles and increased pores when the SiC addition amount reached 20 wt.%.Affected by the addition phase of high modulus and high hardness,the flexural strength and hardness of composites were improved compared with that of Ti3 Al C2 ceramic.When the SiC content was 15 wt.%,the flexural strength and hardness of composite materials reached the highest of 668 MPa and 8.5 GPa,respectively.The fracture toughness of sintered Ti3 Al C2 ceramic is about 7.4 MPa ·m1/2.With the addition of SiC,the fracture toughness of composites changes.When the addition of SiC is 15 wt.%,the fracture toughness of composites is about 7.1 MPa ·m1/2.It is found that the composites has the best comprehensive performance when the adding amount of SiC is 15 wt.%.The wear mechanism of the composites is mainly stripper wear.The friction and wear rate of Ti3 Al C2 ceramic are severe,which the friction coefficient between 2.5-3.2 and the wear rate of 10-3 mm3/N·m.With the addition of SiC,the friction coefficient is significantly reduced(between 0.6 and 1.1),and the wear rate is almost negligible.This is because the hardness and flexural strength of the composites increase significantly after the addition of SiC,which effectively inhibits the fracture and spalling of the composites surface during the friction process and significantly improves the wear resistance of the composites.The tribological properties of composites under different temperatures with SiC counter ball were analyzed.With the increase of the test temperature,the friction coefficient of the composites increased generally,and the wear rate varied between 10-6-10-4 mm3/N·m,showing excellent wear resistance in the wide range of temperature.This is mainly because during the friction process,the debris formed by the fracture of the composites surface were oxidized,and the oxide lubrication film formed by oxidized debris mainly composed of Ti O2,Ti Cx Oy,Si O2 and Al2O3(in Ti3 Al C2 ceramic).The film would protect the material from further wear.