Tribological Properties and Shock Resistances of Aluminum Bronze-Ti₃AlC₂ Composites

On account of the increasing power density and maneuvering characteristics of heavy vehicle, the speed change mechanism faces harsher working conditions. For example, on some vehicles the relative rotate speed of friction plate rise 32%, the pressure of friction plate rise 30%, and the time of sliding friction rise 60%. Under these conditions, friction plates require to possess excellent shock resistance, which avoid the ablation, severe wear and peel off of material. Meanwhile, it is important to adjust and control friction coefficient based on the inertia and shifting parameter of speed change mechanism. If the friction coefficient is too low, friction plate will skid during shifting. It resulted in the irregular change of vehicle speed and deficiency of power. However, if the friction coefficient is too high, the shifting shock will rise during shifting. It causes severe wear and decrease of service life. Therefore, in order to satisfy the needs of high maneuverability, the friction plate must have good tribological performance and shock resistance simultaneously. The using copper-based friction plate occurs violent adhesive wear, thermal failure and wears failure under utmost conditions because of the weak wear resistance and shock resistance. Hence, it is necessary to study new friction plate materials possessing good tribological performance, shock resistance and reliability. At present, the friction layer materials of friction plate mainly include powder metallurgy material, paper-based material, resinous material and ceramic material. The paper-based material and resinous material friction plates crack and fall off easily under high pressure, so they cannot be used on heavy vehicle. The ceramic material friction plate shows poor vibratory shock resistance, which resulted in the large thickness of friction plates. So it is difficult for ceramic material friction plate to install in transmission case. The friction coefficient of ceramic material decreases in water or oil environment, which leads to the reduction of friction plate transfer torque. Therefore, it is more feasible to design the material prescription, preparation technology and structure of powder metallurgy material friction plate. In addition, the aluminium bronzes have good mechanism properties, corrosion resistance and tribological performance. Thus, aluminium bronzes can be used as matrix material to prepare self-lubricating composites. In terms of this issue, the bronze-Ti₃AlC₂ composites and engineering samples were prepared. The friction coefficient, wear rate, impacting coefficient, transfer torque, vibratory shock resistance and thermal shock resistance were tested under different conditions. The mechanical properties, worn surfaces state and friction mechanism were analyzed. Results showed that, Ti₃AlC₂ improved the compressive strength and hardness of composites. Ti₃AlC₂ increased the wear resistance and thermal shock resistance limitation by weakening the adhesive wear. The friction plates containing Ti₃AlC₂ possessed stable transfer torque, and the shock during friction process under heavy load and high speed conditions was weakened by increasing lubricating property. However, the excess Ti₃AlC₂ was harmful to wear resistance and vibratory shock resistance by reducing homogeneity of structure and binding force. After optimizing the content of Ti₃AlC₂, the bronze-Ti₃AlC₂ composites possessed good mechanical properties, tribological performances and shock resistance, which improved the wear resistance, vibratory shock resistance and thermal shock resistance of friction plates under utmost conditions.