Numerical Simulation And Experimental Studies On Friction Properties Of Tial Matrix Self-Lubricating Sliding Bearing

TiAl alloys are widely applied in aerospace industry for the advantages of low density,high elastic modulus and high-temperature strength.However,its applications are limited due to the high friction coefficient and poor wear resistance.TiAl matrix self-lubricating composites reinforced with TiC_0.4 and Ti₃SiC₂were prepared by Spark Plasma Sintering,which enhanced the mechanical and tribological properties of the composites.The XRD analyses of the composites showed that the main phases were TiAl,Ti₃Al,Ti₃SiC₂ and Ti₂Al C.The theoretical densities,Elastic Moduli and Poisson’s ratios were calculated by using the rule of mixtures.The densities,linear expansion coefficients,specific heat capacities and thermal diffusion coefficients of the composites with different Ti₃SiC₂ contents were obtained by the experiments.The new composites were applied to the sliding bearing,and the friction behavior of sliding process was simulated in ABAQUS.It was found that the heat generated by friction was mainly distributed in area of bearing inner surface near end face.The wear of sliding bearing decreased with the increase of temperature,decreased first and then increased with the increase of radial load,and increased rapidly with the increase of rotational speed.The tribological properties of the composites were investigated using the pin-on-disk-type wear testing machine.The experimental results were in better concordance between experimental data and the results of simulation.Ti₃SiC₂ particles in the composites inclined to crack and shed from the matrix at room temperature,which resulted in abrasive wear behavior with high friction coefficient and severe wear.The lubricating properties of Ti₃SiC₂ particles in low load and low sliding speed were difficult to distinguish.As the experimental load was increased to 3 Mpa,the interlayer slip of Ti₃SiC₂ particles was caused by the sufficient friction and shear force and the oxide layer was produced on the surface during high-temperature friction.The tribological properties of the composites were improved by the above temperature and experimental load.As the experimental load was increased to 5 Mpa,the Ti₃SiC₂ particles shed from the matrix for the excessive friction and shear force.Both the friction coefficient and abrasion loss were increased due to the damage of those abrasive particles to the lubrication layer.Under the sliding speed of 0.06 m/s,Ti₃SiC₂ particles could not shed from the matrix in a short time,which resulted in a smooth wear.However,as the sliding speed was increased to 0.48 m/s,more abrasive particles appeared on the friction surface,which resulted in the increase of friction coefficient and abrasion loss.Finally,the friction coefficients,abrasion losses and wear rates of composites under different application environment were considered comprehensively.The optimum experimental conditions of TiAl matrix self-lubricating composites and optimum application environments of the sliding bearings made from the composites were obtained.The optimum application temperature of the sliding bearing made from TiAl matrix self-lubricating composite with 20wt.%Ti₃SiC₂ was 500℃,the optimum application load was 9.42 Mpa,and the optimum rotational speed for application was 2.56 r/s.Under those conditions,the maximum Mises stress was 1.198×10³ Mpa,the maximum temperature rise was 36℃.The optimum experimental temperature of the composite was500℃,the optimum experimental load was 3 Mpa,and the optimum sliding speed for experiment was 0.24 m/s.Under those conditions,the friction coefficient was 0.33,the wear amount was 2.18 mg,the wear rate was 2.02×10^-5 mm³·N^-1·m^-1.