A Novel Method for Adding Graphite Flakes to Al₂O₃–ZrO₂‐Graphite Composites and Performance Testing

A novel method to produce graphite flakes was invented, and this method is good for homogeneous of graphite among the Al₂O₃‐ZrO₂‐Graphite composite powder. Graphite ball, alumina ball, and alumina powder are put into planetary muller together, and the graphite flakes are produced by shear forces between the surface of graphite and alumina ball during the ball mill process. Al₂O₃‐χwt%ZrO₂‐3wt%Graphite (A‐χZ‐3Gr, χ = 5, 10, 15, 20) composites powder are developed by this new method and then are sintered using microwave at a temperature of 1500 °C for 30 min in argon atmosphere. Actually 3wt%Graphite (Gr) is fully capable of forming a lubricating film on the rubbing surface of A‐χZ‐3Gr composites to ensure a low friction coefficient. On the other hand, the ZrO₂ addition is good for the mechanical properties. The effect of ZrO₂ addition on the relative density, hardness, fracture toughness and bending strength of the various A‐χZ‐3Gr composites are investigated. The performance of A‐χZ‐3Gr composites has been greatly improved as compared with Al₂O₃‐3 wt% Graphite sintered under the same condition. The A‐10Z‐3Gr composite exhibited excellent performance such as its relative density, hardness, fracture toughness, bending strength, friction coefficient, and wear rate are 95.4%, 323.7Mpa, 5.8Mpa · m^1/2, 9.3Gpa, 0.31 and 5.19 × 10⁻⁶mm³ Nm⁻¹, respectively.